access-consciousness The mental experiences of which we are aware and have the ability to report on without the capacity to report on how the content was built up by all the neurons, neurotransmitters, and so forth, in the nervous system.

action–outcome When there is a causal relationship between the action and the reward.

action–outcome decision A decision that involves some form of evaluation (not necessarily conscious) of the expected outcomes.

achromatopsia A selective disorder of color perception resulting from a lesion or lesions of the central nervous system, typically in the ventral pathway of the visual cortex. In achromatopsia, the deficit in color perception is disproportionately greater than that associated with form perception. Colors, if perceived at all, tend to be muted.

acquired alexia See alexia.

acquisition The registration of inputs in sensory buffers and sensory analysis stages.

action potential The active or regenerative electrical signal that is required for synaptic communication. Action potentials are propagated along the axon and result in the release of neurotransmitter.

affective Having an emotional value, either positive or negative; not neutral.

affective flexibility The ability to process the relevance of various emotional stimuli depending on a one’s current goals and motivation.

aggregate field theory The belief that the whole brain participates in behavior.

agnosia A neurological syndrome in which disturbances of perceptual recognition cannot be attributed to impairments in basic sensory processes. Agnosia can be restricted to a single modality, such as vision or audition.

agrammatic aphasia Difficulty producing and/or understanding the structure of sentences. Agrammatic aphasia is seen in brain-damaged patients who may speak using only content words, leaving out function words such as the and a.

akinetopsia A selective disorder of motion perception resulting from a lesion or lesions of the central nervous system. Patients with akinetopsia fail to perceive stimulus movement, created by either a moving object or their own motion, in a smooth manner. In severe cases, the patient may only infer motion by noting that the position of objects in the environment has changed over time, as if the patient were constructing dynamics through a series of successive static snapshots.

alexia A neurological syndrome in which the ability to read is disrupted. Alexia is frequently referred to as acquired alexia to indicate that it results from a neurological disturbance such as a stroke, usually including the occipitoparietal region of the left hemisphere. In contrast, refers to problems in reading that are apparent during childhood development. The phrases and developmental dyslexia are commonly used to indicate that reading is abnormal, either from a neurological disturbance of as part of development.

alpha motor neurons The neurons that terminate on muscle fibers, causing contractions that produce movements. Alpha motor neurons originate in the spinal cord and exit through the ventral root of the cord.

amnesia Deficits in learning and memory ability following brain damage or disease.

amobarbital A barbiturate used to produce rapid and brief anesthesia.

amygdala Groups of neurons anterior to the hippocampus in the medial temporal lobe that are involved in emotional processing.

analytic processing Perceptual analysis that emphasizes the component parts of an object. Reading is thought to be a prime example of analytic processing in that the recognition of words requires the analysis of at least some of the component letters. Compare holistic processing.

angiography An imaging method used to evaluate the circulatory system in the brain.

anomia A type of aphasia in which the person has difficulty generating the words used to label things in the world.

anterior cingulate cortex Anterior portion of the cingulate cortex, located below the frontal lobe along the medial surface. This region is characterized by a primitive cytoarchitecture (three-layered cortex) and is part of the interface between the frontal lobe and the limbic system. The anterior cingulate cortex is implicated in various executive functions, such as response monitoring, error detection, and attention.

anterior commissure The nerve bundle connecting the left and right cerebral hemispheres and that is located anterior to the corpus callosum.

anterograde amnesia The loss of the ability to form new memories. Compare retrograde amnesia.

aphasia A language deficit following brain damage or disease.

apperceptive agnosia A form of agnosia associated with deficits in the operation of higher-level perceptual analyses. A patient with apperceptive agnosia may recognize an object when seen from a typical viewpoint. However, if the orientation is unusual, or the object is occluded by shadows, recognition deteriorates. Compare associative agnosia.

apraxia A neurological syndrome characterized by loss of skilled or purposeful movement that cannot be attributed to weakness or an inability to innervate the muscles. Apraxia results from lesions of the cerebral cortex, usually in the left hemisphere.

apraxia Difficulty pronouncing words.

arcuate fasciculus A white matter tract that connects the posterior temporal region with frontal brain regions and is believed to transmit language-related information between the posterior and anterior brain regions.

area MT A region in the visual cortex containing cells that are highly responsive to motion. Area MT is part of the dorsal pathway, thought to play a role not only in motion perception but also in representing spatial information.

area V4 A region in the visual cortex containing cells that are thought to process color information.

association cortex The volume of the neocortex that is not strictly sensory or motor, but receives inputs from multiple sensorimotor modalities.

associationism The theory that the aggregate of a person’s experience determines the course of mental development.

associative agnosia A form of agnosia in which the patient has difficulty linking perceptual representations with long-term knowledge of the percepts. For example, the patient may be able to identify that two pictures are of the same object, yet fail to demonstrate an understanding of what the object is used for or where it is likely to be found. Compare apperceptive agnosia.

ataxia A movement disorder associated with lesions or atrophy of the cerebellum. Ataxic movements are clumsy and erratic, even though muscle strength is normal.

attentional blink A phenomenon often observed during rapid serial presentations of visual stimuli, in which a second salient target that is presented between 150-450 ms after the first one goes undetected.

autism A neurological disorder characterized by deficits in social cognition and social communication often associated with an increase in repetitive behavior or obsessive interests.

autonomic motor system See autonomic nervous system.

autonomic nervous system Also autonomic motor system or visceral motor system. The body system that regulates heart rate, breathing, and glandular secretions and may become activated during emotional arousal, initiating a “fight or flight” behavioral response to a stimulus. It has two subdivisions, the sympathetic and parasympathetic branches.

axon The process extending away from a neuron down which action potentials travel. The terminals of axons contact other neurons at synapses.

axon collateral Branches off an axon that can transmit signals to more than one cell.

axon hillock A part of the cell body of a neuron where the membrane potentials are summated before being transmitted down the axon.

backward referral hypothesis Libet’s hypothesis that the awareness of a neural event is delayed approximately 500 milliseconds after the onset of the stimulating event, and this awareness is referred back in time to the onset of the stimulating event.

Bálint’s syndrome A disorder following bilateral occipitoparietal stroke, characterized by difficulty in perceiving visual objects. Patients with the disorder can correctly identify objects but have difficulty relating objects to one another. They tend to focus attention on one object to the exclusion of others when the objects are presented simultaneously.

basal ganglia A collection of five subcortical nuclei: the caudate, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. The basal ganglia are involved in motor control and learning. Reciprocal neuronal loops project from cortical areas to the basal ganglia and back to the cortex. Two prominent basal ganglia disorders are Parkinson’s disease and Huntington’s disease.

basic emotion An emotion with unique characteristics, carved by evolution, and reflected through facial expressions.

BBB See blood–brain barrier.

behaviorism The theory that environment and learning are the primary factors in mental development, and that people should be studied by outside observation.

blindsight Residual visual abilities within a field defect in the absence of awareness. Blindsight can be observed when there is damage in the primary visual cortex. The residual function is usually observed with indirect measures such as by prodding the patient to look at or point to the location of a stimulus, even if the patient denies having seen the stimulus.

block design experiment An experiment in which the recorded neural activity is integrated over a “block” of time during which the participant is either presented a stimulus or performs a task. The recorded activity pattern is then compared to other blocks that have been recorded while doing the same task or stimulus, a different task or stimulus, or nothing at all.

blood–brain barrier (BBB) A physical barrier formed by the end feet of astrocytes between the blood vessels in the brain and the tissues of the brain. The BBB limits which materials in the blood can gain access to neurons in the nervous system.

blood oxygen level–dependent (BOLD) The BOLD signal is the change in magnetic resonance signal intensity of hydrogen ion concentration in the brain, which results from changes in local tissue oxygenation state. When neurons become more active, this triggers an increase in the amount of oxygenated blood entering local capillaries in the tissue. This alters the ratio of oxygenated to deoxygenated hemogloblin in the tissue. Because deoxygenated hemogloblein is paramagnetic, it disrupts the local magnetic properties of the tissue, and the MR signal intensity drops. Conversely, when oxygenated blood increases in response to local neuron activity, the MR signal intensity increases, and this is known as the BOLD response. The BOLD signal is an indirect measure of neural activity, and is delayed with respect to the neural activity that leads to the BOLD signal, taking about 2–3 seconds to begin, and about 5–6 seconds after the onset of neural activity to peak.

BMI See brain–machine interface.

BOLD See blood oxygen level–dependent.

bottleneck A stage of processing where not all of the inputs can gain access or pass through.

bradykinesia Slowness in the initiation and execution of movements. Bradykinesia is a prominent symptom in Parkinson’s disease.

brain graph A visual model of the connections within some part of the nervous system.

brain lesion Structural damage to the white or gray matter of the brain. Lesions result from many causes, including tumor, stroke, and degenerative disorders such as Alzheimer’s disease.

brain–machine interface (BMI) A device that uses the interpretation of neuronal signals to perform desired operations with a mechanical device outside the body. For instance, signals recorded from neurons or EEG can be used to move a prosthetic arm.

brainstem The region of the nervous system that contains groups of motor and sensory nuclei, nuclei of widespread modulatory neurotransmitter systems, and white matter tracts of ascending sensory information and descending motor signals.

Broca’s aphasia The oldest and perhaps best-studied form of aphasia, characterized by speech difficulties in the absence of severe comprehension problems. However, Broca’s aphasics may also suffer from problems in fully comprehending grammatically complex sentences. Compare Wernicke’s aphasia.

Broca’s area An area located in the left hemisphere of the frontal cortex that is important to language production.

CAT See computed tomography.

category-specific deficit Recognition impairment that is restricted to a certain class of objects. Some rare individuals demonstrate an impairment in their ability to recognize living things, yet exhibit near-normal performance in recognizing nonliving things. Such deficits are useful in the development of models about how perceptual and semantic knowledge is organized in the brain.

cellular architecture See cytoarchitectonics.

central nervous system (CNS) The brain and spinal cord. Compare peripheral nervous system.

central sulcus The deep fold or fissure between the frontal and parietal cortex that separates the primary motor cortex from the primary somatosensory cortex.

central pattern generator A neural network limited to the spinal cord that produces patterned motor outputs without descending commands from the cerebral cortex or sensory feedback.

cerebellum Also known as “little cerebrum.” A large, highly convoluted (infolded) structure located dorsal to the brainstem at the level of the pons. The cerebellum maintains (directly or indirectly) interconnectivity with widespread cortical, subcortical, brainstem, and spinal cord structures, and plays a role in various aspects of coordination ranging from locomotion to skilled, volitional movement.

cerebral cortex The layered sheet of neurons that overlies the forebrain. The cerebral cortex consists of neuronal subdivisions (areas) interconnected with other cortical areas, subcortical structures, and the cerebellum and spinal cortex.

cerebral specialization The adaptation of the activity in a particular brain region to subserve a given cognitive function or behavior.

cerebral vascular accident A rapid loss of brain function due to a compromise in the blood supply to the brain secondary to arterial occlusion or hemorrhage.

chaotic systems Systems that are highly sensitive to initial conditions. Although their future behavior is determined by their initial conditions, approximate determinations of these initial conditions cannot be used to approximate the future condition.

chemical senses The two senses that depend on environmental molecules for stimulation: taste and smell.

CNS See central nervous system.

cognitive control Processes that facilitate information processing. Control operations are thought to help coordinate activity across different neural regions; for example, the representation of a current goal in the prefrontal cortex can help control the retrieval of information in long-term memory. See also executive functions.

cognitive neuroscience The study of how the brain enables the mind.

cognitive psychology The branch of psychology that studies how the mind internally represents the external world and performs the mental computations required for all aspects of thinking. Cognitive psychologists study the vast set of mental operations associated with such things as perception, attention, memory, language, and problem solving.

commissure White matter tracts that cross from the left to the right side, or vice versa, of the central nervous system.

complex emotion Combinations of basic emotions, some of which may be socially or culturally learned, that can be identified as evolved, long-lasting feelings.

complex system A system composed of many interconnected parts, such that when the parts self-organize into a single system, the resulting system exhibits one or more properties not obvious from the properties of the individual parts.

computed tomography (CT or CAT) An noninvasive neuroimaging method that provides images of internal structures such as the brain. CT is an advanced version of the conventional X-ray. Whereas conventional X-rays compress three-dimensional objects into two dimensions, CT allows for the reconstruction of three-dimensional space from the compressed two-dimensional images through computer algorithms.

conduction aphasia A form of aphasia that is considered a disconnection syndrome. Conduction aphasia may occur when the arcuate fasciculus, the pathway from Wernicke’s area to Broca’s area, is damaged, thereby disconnecting the posterior and anterior language areas.

consciousness The human ability to be aware of some of the contents of mental activity and potentially describe these mental states to other individuals.

consolidation The process by which memory representations become stronger over time. Consolidation is believed to include changes in the brain system participating in the storage of information.

core affect A mental representation of the sensory input from the body and from the world.

corpus callosum A fiber system composed of axons that connect the cortex of the two cerebral hemispheres.

corpuscle A globular mass of cells that are part of the somatosensory system.

cortical visual areas Regions of visual cortex that are identified on the basis of their distinct retinotopic maps. The areas are specialized to represent certain types of stimulus information, and through their integrated activity they provide the neural basis for visually based behavior.

corticospinal tract (CST) Also pyramidal tract. A bundle of axons that originate in the cortex and terminate monosynaptically on alpha motor neurons and spinal interneurons in the spinal cord. Many of these fibers originate in the primary motor cortex, although some come from secondary motor areas. The corticospinal tract is important for the control of voluntary movements.

covert attention The ability to direct attention without overt alterations or changes in sensory receptors—for example, attending to a conversation without turning the eyes and head toward the speakers.

CT See computed tomography.

cytoarchitectonics The way in which cells differ between brain regions.

DBS See deep-brain stimulation.

decoding Using the brain activity, which is produced by a stimulus and detected by such methods as fMRI, in order to determine the original stimulus.

declarative memory Knowledge to which we have conscious access, including personal and world knowledge (events and facts). The term declarative signals the idea that declarations can be made about this knowledge, and that for the most part, we are aware that we possess the information. Compare nondeclarative memory.

deep-brain stimulation (DBS) The electrical stimulation of brain structures via an implanted electrode. Stimulation of the subthalamic nucleus, one of the nuclei of the basal ganglia, is used as a treatment for Parkinson’s disease.

default network A network of brain areas that is active when a person is at wakeful rest and not engaged with the outside world.

degenerative disorders Disorders or diseases, either genetic or environmental, in which the function or structure of the affected tissues will continue to deteriorate over time.

delayed-response task A task in which the correct response must be produced after a delay period of several seconds. Such tasks require the operation of working memory because the animal or person must maintain a record of the stimulus information during the delay period.

dendrites Large treelike processes of neurons that receive inputs from other neurons at locations called synapses.

depolarization A change in the membrane potential in which the electrical current inside the cell becomes less negative. With respect to the resting potential, a depolarized membrane potential is closer to the firing threshold. Compare hyperpolarization.

descriptive decision theory Theories that attempt to describe what people actually do, not what they should do.

developmental alexia See alexia.

dichotic listening An experimental technique in which subjects listen to a different message in each ear at the same time.

dichotic listening task An auditory task in which two competing messages are presented simultaneously, one to each ear, while the subject tries to report only one or both messages. The ipsilateral projections from each ear are presumably suppressed when a message comes over the contralateral pathway from the other ear.

diffusion tensor imaging (DTI) A neuroimaging technique employed using an MRI scanner that allows white matter pathways in the brain to be imaged.

dimensions of emotion A way to describe emotions that are fundamentally the same but that differ along one or more dimensions, such as valence (pleasant or unpleasant, positive or negative) and arousal (very pleasant to very unpleasant).

distributed representation The idea that information may be stored in large populations of neurons located in relatively widespread regions of the brain. This idea is in contrast to the idea that the representations of some items in memory are stored in a discrete, highly localized set of neurons.

dopamine An organic chemical amine that in the brain functions as a neurotransmitter. It is formed from L-DOPA by removing a carboxyl group.

dorsal (occipitoparietal) stream A processing pathway for visual stimuli that is specialized for spatial perception—for determining where an object is—and for analyzing the spatial configuration between different objects in a scene.

double dissociation A method used to develop functional models of mental and/or neural processes. Evidence of a double dissociation requires a minimum of two groups and two tasks. In neuropsychological research, a double dissociation is present when one group is impaired on one task and the other group is impaired on the other task. In imaging research, a double dissociation is present when one experimental manipulation produces changes in activation in one neural region and a different manipulation produces changes in activation in a different neural region. Double dissociations provide a strong argument that the observed differences in performance reflect functional differences between the groups, rather than unequal sensitivity of the two tasks. Compare single dissociation.

DTI See diffusion tensor imaging.

dualism A major philosophical approach to describing consciousness, which holds that the mind and brain are two separate phenomena. Variations include popular dualism, property dualism, epiphenomenalism, and interactionist property dualism.

dura mater Dense layers of collagenous fibers that surround the brain and spinal cord.

dynamic filtering The hypothesis that a key component of working memory involves the selection of information that is most relevant, given current task demands. This selection is thought to be accomplished through the filtering, or exclusion of, potentially interfering and irrelevant information.

dysarthria Difficulty saying words.

dyslexia See alexia.

early selection The theoretical model positing that attention can select (partially or completely) incoming information prior to complete perceptual analysis and its encoding as categorical or semantic information. Compare late selection.

EEG See electroencephalography.

effector Any part of the body that can move, such as an arm, finger, or leg.

electrical gradient A force that develops when a charge distribution across the neuronal membrane develops such that the charge inside is more positive or negative than the one outside. Electrical gradients result from asymmetrical distributions of ions across the membrane.

electrocortogram (ECoG) A method to record electrical activity from the cerebral cortex by placing electrodes directly on the surface of the brain, either outside the dura or beneath it.

electroencephalography (EEG) A technique to measure the electrical activity of the brain. In EEG, surface recordings are made with electrodes placed on the scalp. The EEG signal includes endogenous changes in electrical activity (e.g., due to changes in arousal), as well as those triggered by specific events (e.g., stimuli or movements).

electrotonic conduction Passive current flow through neurons that accompanies activated electrical currents.

emergence The appearance of a new, previously nonexistent, structure with a new level of organization and new properties, which occurs from the self-organization of a complex system.

emotion An affective (positive or negative) mental response to a stimulus that is comprised of a physiological response, a behavioral response, and a subjective experience (e.g., by change in heart rate, facial expression, and speech).

emotion generation Typically a combination of a bottom up emotional response in combination with a top down emotional response that involves memory and linguistic representation.

emotion regulation Intentionally regulating how we experience and respond to our emotions.

emotional stimulus A stimulus that is highly relevant for the well-being and survival of the observer and automatically provokes an emotion.

empathic accuracy The ability to accurately infer the thoughts, feelings and/or emotional state of another person.

empathy The ability to experience and understand what others feel while still knowing the difference between oneself and others. Empathy is often described as the ability to “put oneself in another person’s shoes.”

empiricism The idea that all knowledge comes from sensory experience.

encoding The processing of incoming information to be stored. Encoding consists of two stages: acquisition and consolidation. Compare retrieval.

encoding model A model of how information in the environment is represented. Encoding models are used in fMRI to predict the BOLD response to different stimuli.

endogenous cuing The control of attention by internal stimuli under voluntary control. Compare exogenous cuing.

endpoint control A hypothesis concerning how movements are planned in terms of the desired final location. Endpoint control models emphasize that the motor representation is based on the final position required of the limbs to achieve the movement goal.

episodic memory Stored information about events in one’s life, including information about when they happened and what happened. Episodic memory is a form of declarative memory.

equilibrium potential The membrane potential at which a given ion (e.g., K+) has no net flux across the membrane; that is, as many of the ions move outward as inward across the membrane.

ERN See error-related negativity.

ERP See event-related potential.

error-related negativity (ERN) An electrical signal that is derived from the EEG record following an erroneous response. The ERN is seen as a prominent negative deflection in the ERP, and it is hypothesized to originate in the anterior cingulate.

event-related design A paradigm used in fMRI studies in which the BOLD response can be time-locked to particular stimuli or responses. Such designs require using delays or temporal variation in order to isolate the response to these events.

event-related potential (ERP) A change in electrical activity that is time-locked to specific events such as the presentation of a stimulus or the onset of a response. When the events are repeated many times, averaging the EEG signals reveals the relatively small changes in neural activity triggered by these events. In this manner, the background fluctuations in the EEG signal are removed, revealing the event-related signal with great temporal resolution.

exogenous cuing Also reflexive cuing. The control of attention by external stimuli and not by internal voluntary control. Compare endogenous cuing.

extinction The failure to perceive or respond to a stimulus contralateral to a lesion (contralesional) when presented with a simultaneous stimulus ipsilateral to the lesion (ipsilesional).

extrapyramidal tracts A collection of motor tracts that originate in various subcortical structures, including the vestibular nucleus and the red nucleus. These tracts are especially important for maintaining posture and balance.

extrastriate body area (EBA) A functionally-defined area in the lateral occipitotemporal cortex that has been found, in fMRI studies, to show a stronger response to images containing body parts relative to other animate and inanimate stimulus categories.

extrastriate visual areas Visual areas that lie outside the striate cortex (Brodmann area 17, the primary visual cortex) and are considered secondary visual areas because they receive input either directly or indirectly from the primary visual cortex.

facial expression The nonverbal communication of emotion by manipulation of particular groups of facial muscles. Research findings suggest six basic human facial expressions represent the emotional states anger, fear, disgust, happiness, sadness, and surprise.

False-Belief Task A task that measures the ability to simultaneously represent the individual, and sometimes different, mental states of at least two different people.

familiarity A memory that does not contain episodic awareness of the prior event but is recognized by the feeling that the item was seen before—that is, by its feeling familiar.

fear conditioning Learning in which a neutral stimulus acquires aversive properties by virtue of being paired with an aversive event.

feature integration theory of attention A psychological theory of visual perception based on the idea that the visual system can process in parallel elementary features such as color, shape, and motion, but requires spatial attention to bind the features that define an object.

feeling Either the sensation of touch or the conscious sensation of an emotion.

FFA See fusiform face area.

fissure See sulcus.

flow Described by psychologist Mihaly Csikszentmihalyi, the enjoyable state of being “in the zone.” He suggests that people are really happy when totally immersed in a challenging task that closely matches their abilities.

fMRI See functional magnetic resonance imaging.

forward model A theoretical construct referring to the idea that the brain generates predictions of expected events. In motor control, a forward model refers to the prediction of the expected sensory consequences of a movement.

fovea The central region of the retina that is densely packed with cone cells and provides high-resolution visual information.

free-rider A person who benefits from another’s goods or services with no cost to him/herself.

frontal lobe The mass of cortex anterior to the central sulcus and dorsal to the Sylvian fissure. The frontal lobe contains two principal regions—the motor cortex and the prefrontal cortex—each of which can be further subdivided into specific areas both architectonically and functionally.

frontal pole (FP) The most anterior part of the prefrontal cortex, including area 10 and parts of area 9. This region is hypothesized to play a critical role in the hierarchical representation of action goals.

functional asymmetries Differences in the functions that each hemisphere subserves.

functional magnetic resonance imaging (fMRI) A neuroimaging method that utilizes MRI to track blood flow changes in the brain that are thought to be correlated with local changes in neuronal activity.

fusiform body area (FBA) See extrastriate body area (EBA)

fusiform face area (FFA) A functionally defined area of the brain, located in the ventral surface of the temporal lobe in the fusiform gyrus, that responds to selective stimuli, such as faces.

fusiform gyrus A gyrus located along the ventral surface of the temporal lobe. This area has been shown in neuroimaging studies to be consistently activated when people view face stimuli. Neurological lesions that include the fusiform gyrus are associated with prosopagnosia, although the damage also extends to other regions of the cortex.

ganglion cell A type of neuron in the retina. Ganglion cells receive input from the photoreceptors (rods and cones) and intermediate cells of the retina and send axons to the thalamus and other subcortical structures.

glial cell Also neuroglial cell. One of two cell types (along with the neuron) in the nervous system. Glial cells are more numerous than neurons, by perhaps a factor of 10, and may account for more than half of the brain’s volume. They typically do not conduct signals themselves; but without them, the functionality of neurons would be severely diminished. Tissue made of glial cells is termed glia.

global aphasia A severe form of aphasia in which the patient has profound difficulty in both the comprehension of language and production of speech.

glomeruli (s. glomerulus) The neurons of the olfactory bulb.

gnostic unit A neuron or small set of neurons tuned for a specific percept (e.g., an apple). The concept of the gnostic unit is based on the idea that hierarchical models of perception imply that, at higher levels in the system, neurons become much more selective in terms of what they respond to.

goal-oriented action Actions that are planned and produced to achieve a particular result. Goal-oriented actions stand in contrast to more habitually or stimulus driven behavior and are strongly under the control of reinforcement.

goal-oriented behavior Behavior that allows us to interact in the world in a purposeful manner. Goals reflect the intersection of our internal desires and drives, coupled with the current environmental context.

gray matter Regions of the nervous system that contain primarily neuronal cell bodies. Gray matter includes the cerebral cortex, the basal ganglia, and the nuclei of the thalamus. Gray matter is so called because, in preservative solution, these structures look gray in comparison to the white matter where myelinated axons are found (which look more white).

gyrus (pl. gyri) A protruding rounded surface of the cerebral cortex that one can see upon gross anatomical viewing of the intact brain. Compare sulcus.

habit A response that is under stimulus control. Habits are formally defined as behaviors that occur independently of reinforcement. For example, if the reward is no longer given to a stimulus, the persistent response is referred to as a habit.

handedness The tendency to perform the majority of one’s manual actions with either the right or left hand.

Hebbian learning The theory that, if a weak and a strong input act on a cell at the same time, the weak synapse becomes stronger. The theory is named for Donald Hebb, who postulated this mechanism as a means for the connectional strength between neurons to change in order to store information.

hemianopia A condition resulting from destruction of the primary visual cortex in one hemisphere. The patient is unaware of any visual stimulation presented in the side of space contralateral to the lesion.

hemiplegia A neurological condition characterized by the loss of voluntary movements on one side of the body. Hemiplegia typically results from damage to the corticospinal tract, either from lesions to the motor cortex or from white matter lesions that destroy the descending fibers.

heterotopic areas Noncorresponding areas of the brain. Usually such areas are referred to as heterotopic because of their connections with one another. For instance, a connection between M1 on the left side and V2 on the right side would be a connection joining heterotopic areas of the brain. Compare homotopic areas.

hierarchical structure A configuration that may be described at multiple levels, from global features to local features; the finer components are embedded within the higher level components.

hippocampus (pl. hippocampi) The “seahorse” of the brain. A layered structure in the medial temporal lobe that receives inputs from wide regions of the cortex via inputs from the surrounding regions of the temporal lobe, and sends projections out to subcortical targets. The hippocampus is involved in learning and memory, particularly memory for spatial locations in mammals and episodic memory in humans.

holistic processing Perceptual analysis that emphasizes the overall shape of an object. Face perception has been hypothesized to be the best example of holistic processing, in that the recognition of an individual appears to reflect the composition of the person’s facial features rather than being based on the recognition of the individual features themselves. Compare analytic processing.

homotopic areas Areas in corresponding locations in the two hemispheres. A connection between M1 on the right side and M1 on the left side would be joining homotopic areas. Compare heterotopic areas.

homunculus See primary somatosensory cortex.

Huntington’s disease A genetic degenerative disorder in which the primary pathology, at least in the early stages of the disease, is observed in the striatum (caudate and putamen) of the basal ganglia. Prominent symptoms include clumsiness and involuntary movements of the head and trunk. Cognitive impairments are also seen and become pronounced over time. Compare Parkinson’s disease.

hyperpolarization A change in the membrane potential in which the electrical current inside of the cell becomes more negative. With respect to the resting potential, a hyperpolarized membrane potential is farther from the firing threshold. Compare depolarization.

hypokinesia A movement disorder characterized by the absence or reduction in the production of movement. Hypokinesia is a prominent symptom of Parkinson’s Disease.

hypothalamus A small collection of nuclei that form the floor of the third ventricle. The hypothalamus is important for the autonomic nervous system and the endocrine system, and it controls functions necessary for the maintenance of homeostasis.

ideational apraxia A severe form of apraxia in which the patient’s knowledge about the intent of an action is impaired. For example, the patient may no longer comprehend the appropriate use for a tool, even though still capable of producing the required movement. Compare ideomotor apraxia.

ideomotor apraxia A form of apraxia in which the patient has difficulty executing the desired action properly. Patients with ideomotor apraxia appear to have a general idea about how the action should be performed and how tools are used, but they are unable to coordinate the movements to produce the action in a coherent manner. Compare ideational apraxia.

imitative behavior The spontaneous and uncontrolled mimicking of another person’s behavior that is sometimes exhibited by patients with frontal lobe damage.

inferior colliculus A part of the midbrain that is involved in auditory processing. Compare superior colliculus.

inhibition of return (IOR) A hypothesized process underlying the slowing of motor responses observed over time when attention is reflexively attracted to a location by a sensory event (i.e., reflexive cue). As the name implies, inhibition of return is conceptualized as inhibition of recently attended locations such that attention is inhibited in returning to that location (or object).

inhibitory control The hypothesis that one aspect of executive functions is the regulation of habitual responses or environmentally dictated actions by active inhibition. A loss of inhibitory control is assumed to underlie the tendency of some patients with prefrontal lesions to produce socially inappropriate behavior.

insula A part of cortex known to process gustatory information.

integrative agnosia A form of agnosia associated with deficits in the recognition of objects due to the failure to group and integrate the component parts into a coherent whole. Patients with this deficit can faithfully reproduce drawings of objects; however, their percept is of isolated, unconnected parts or contours.

interaural time The difference in time between when a sound reaches each of the two ears. This information is represented at various stages in the auditory pathway and provides an important cue for sound localization.

interoception Physical sensations arising from inside the body such as pain, temperature, hunger, etc.

interpreter A left-brain system that seeks explanations for internal and external events in order to produce appropriate response behaviors.

ion channel A passageway in the cell membrane, formed by a transmembrane protein that creates a pore, through which ions (charged atoms in solution) of sodium, potassium, and chloride (Na+, K+, and Cl–) might pass into or out of the cell.

ion pump Proteins in the cellular membrane of neurons that are capable of transporting ions against their concentration gradient. The sodium-potassium pump transports sodium ions out of the neuron and potassium ions into the neuron.

joint attention The ability to monitor someone else’s attention by observing that person’s gaze or actions and directing one’s own attention similarly.

knockout procedure A technique for creating a genetically altered version of a species. In the knockout species, specific genes are altered or eliminated. Knockout procedures can be used to study behavioral changes occurring in animals that have developed without the targeted gene, or to observe how genes code the development of the nervous system.

late selection The theoretical model positing that all inputs are equally processed perceptually, but attention acts to differentially filter these inputs at later stages of information processing. Compare early selection.

lateral fissure See Sylvian fissure.

lateral geniculate nucleus (LGN) The thalamic nucleus that is the main target of axons of the optic tract. Output from the LGN is directed primarily to the primary visual cortex (Brodmann area 17). Compare medial geniculate nucleus.

lateral occipital complex (or cortex) (LOC) A region of extrastriate cortex that is part of the ventral pathway. Processing in LOC is essential for shape perception and recognition.

lateral prefrontal cortex (LPFC) The region of the cerebral cortex that lies anterior to Brodmann area 6, along the lateral surface. This region has been implicated in various executive functions, such as working memory and response selection.

layer A common organizational cluster of neurons in the central nervous sytem.

learning The process of acquiring new information.

lexical access The process by which perceptual inputs activate word information in the mental lexicon, including semantic and syntactic information about the word.

lexical integration The function of words being integrated into a full sentence, discourse, or large current context to discern the message.

lexical selection The process of selecting from a collection of representations the activated word that best matches the sensory input.

LGN See lateral geniculate nucleus.

limbic system Several structures that form a border (limbus in Latin) around the brainstem, named the grand lobe limbique (“limbic lobe”) by Paul Broca. The limbic system is the emotional network that includes the amygdala, orbitofrontal cortex, and portions of the basal ganglia.

limited capacity The concept that the stages of information processing have a finite processing capability, leading to the need for the system to select high-priority information for access to these stages of analysis.

long-term memory The retention of information over the long term, from hours to days and years. Compare sensory memory and short-term memory.

M1 See primary motor cortex.

magnetic resonance imaging (MRI) A neuroimaging technique that exploits the magnetic properties of organic tissue. Certain atoms are especially sensitized to magnetic forces because of the number of protons and neutrons in their nuclei. The orientation of these atoms can be altered by the presence of a strong magnetic field. A radio frequency signal can be used to knock these aligned atoms from their orientation in the magnetic field. The atoms will then realign with the magnetic field and give off a radio frequency signal that can be measured by sensitive detectors. Structural MRI studies usually measure variations in the density of hydrogen ions in the tissue being scanned. Functional MRI measures changes over time in the signal intensity of the targeted atom.

magnetoencephalography (MEG) A measure of the magnetic signals generated by the brain. The electrical activity of neurons also produces small magnetic fields, which can be measured by sensitive magnetic detectors placed along the scalp, similar to the way EEG measures the surface electrical activity. MEG can be used in an event-related manner similar to ERP studies, with similar temporal resolution. The spatial resolution, in theory, can be superior with MEG because magnetic signals are minimally distorted by organic tissue such as the brain or skull.

materialism A major philosophical approach to describing consciousness, based on the theory that the mind and brain are both physical mediums. Variations include: philosophical behaviorism, reductive materialism, and functionalism.

medial frontal cortex (MFC) The medial region of the frontal cortex that includes parts of areas 24, 32, and inferior aspects of 6 and 8. The medial frontal cortex is associated with cognitive control—in particular, monitoring functions for error detection and resolving conflict.

medial geniculate nucleus (MGN) A collection of cell bodies in the medial portion of the thalamus involved in processing auditory information. Output from the MGN is directed primarily to the primary auditory cortex. Compare lateral geniculate nucleus.

medulla Also myelencephalon. The brainstem’s most caudal portion. The medulla is continuous with the spinal cord and contains the prominent, dorsally positioned nuclear groups known as the gracile and cuneate nuclei, which relay somatosensory information from the spinal cord to the brain, and the ventral pyramidal tracts, containing descending projection axons from the brain to the spinal cord. Various sensory and motor nuclei are found in the medulla.

MEG See magnetoencephalography.

memory The persistence of learning in a state that can be revealed later.

mental lexicon A mental store of information about words, including semantic information (meanings of the words), syntactic information (rules for using the words), and the details of word forms (spellings and sound patterns).

mesocortical pathway A path through which dopaminergic projections travel to reach the neocortex.

MGN See medial geniculate nucleus.

microstimulation Injection of electrical current in the vicinity of a group of neurons of interest, in order to induce neural activity. Microstimulation allows the experimenter to manipulate normal neural activity and observe the consequences on behavior.

midbrain The part of the brain consisting of the tectum (meaning “roof,” and representing the dorsal portion of the mesencephalon), tegmentum (the main portion of the midbrain), and ventral regions occupied by large fiber tracts (crus cerebri) from the forebrain to the spinal cord (corticospinal tract), cerebellum, and brainstem (corticobulbar tract). The midbrain contains neurons that participate in visuomotor functions (e.g., superior colliculus, oculomotor nucleus, trochlear nucleus), visual reflexes (e.g., pretectal region), auditory relays (inferior colliculus), and the mesencephalic tegmental nuclei involved in motor coordination (red nucleus). It is bordered anteriorly by the diencephalon, and caudally by the pons.

mirror neuron Neurons that show similar responses when an animal is performing an action or observing that action produced by another organism. Mirror neurons are hypothesized to provide a strong link between perception and action, perhaps providing an important basis for the development of conceptual knowledge.

mirror system A distributed network of neurons that respond not only to one’s own action but also to perceived actions. For instance, a mirror neuron responds when you pick up a pencil and when you watch someone else pick up a pencil.

module A specialized processing unit of the nervous system. Modules are hypothesized to perform specific computations; for example, some theorists believe there are dedicated modules for speech perception, distinct from those used for auditory perception.

monitoring The executive function associated with evaluating whether current representations and/or actions are conducive to the achievement of current goals. Errors can be avoided or corrected by a monitoring system. One of the hypothesized operations of a supervisory attentional system.

Montreal procedure Created by Wilder Penfield and Herbert Jasper, a procedure to treat epilepsy in which the neurons that produced seizures were surgically destroyed.

morpheme Morphemes are the smallest grammatical units of a language that carry bits of meaning. They may or may not be whole words; for example, dog, spit, un- and –ly are morphemes.

multiple realizability A philosophy of mind thesis that contends that a single mental state or event (such as pain) can be realized by many different physical states or events.

MRI See magnetic resonance imaging.

multisensory integration The integration of information from more than one sensory modality. Watching someone speak requires the integration of auditory and visual information.

multiunit recording A physiological procedure in which an array of electrodes is inserted in the brain such that the activity of many cells can be recorded simultaneously.

myelencephalon See medulla.

myelin A fatty substance that surrounds the axons of many neurons and increases the effective membrane resistance, helping to speed the conduction of action potentials.

N400 response Also simply “the N400.” A negativepolarity event-related potential that is elicited by words, and that is larger in amplitude for words that do not fit well into the sentence context. Compare P600 response.

neglect See unilateral spatial neglect.

neocortex The portion of the cortex that typically contains six main cortical layers (with sublayers) and has a high degree of specialization of neuronal organization. The neocortex is composed of areas like the primary sensory and motor cortex and association cortex, and as its name suggests, is the most modern (evolved) type of cortex.

neural circuit Groups of interconnected neurons that process specific kinds of information.

neural network Computer model in which processing is distributed over units whose inputs and outputs represent specific features. For example, they may indicate whether a stimulus contains a visual feature, such as a vertical or horizontal line.

neural system Groups of neural circuits that combine to form larger systems for processing information. For example, the visual system is a system comprising many smaller more specialized neural circuits.

neuroeconomics An emerging field of brain science that combines economics and cognitive neuroscience with the goal of understanding the neural mechanisms involved in decision making.

neuron One of two cell types (along with the glial cell) in the nervous system. Neurons are responsible for processing sensory, motor, cognitive, and affective information.

neuron doctrine The concept proposed by the great Spanish neuroanatomist Santiago Ramon y Cajal in the 19th century that the neuron is the fundamental unit of the nervous system, and that the nervous system is composed of billions of these units (neurons) connected to process information.

neurophysiology The study of the physiological processes of the nervous system. Neural activity is characterized by physiological changes that can be described both electrically and chemically. The changes can be observed at many different levels, ranging from the gross changes recorded with EEG, to the firing of individual neurons, to the molecular changes that occur at the synapse.

neurotransmitter A chemical substance that transmits the signal between neurons at chemical synapses.

nociceptors The somatosensory receptors that convey pain information.

node of Ranvier A location at which myelin is interrupted between successive patches of axon, and where an action potential can be generated.

nondeclarative memory Knowledge to which we typically have no conscious access, such as motor and cognitive skills (procedural knowledge). For example, the ability to ride a bicycle is a nondeclarative form of knowledge. Although we can describe the action itself, the actual information one needs to ride a bicycle is not easy to describe. Compare declarative memory.

normative decision theory A theory of how actions are selected in which the basic premise is that the agent makes the optimal choice, having considered the possible rewards and costs associated with each option.

nucleus (pl. nuclei) 1. In neuroanatomy, a collection of cell bodies in the central nervous system—for example, the lateral geniculate nucleus. 2. In biology, a cellular organelle where DNA is stored.

nucleus accumbens The ventral part of the striatum, one of the nuclei of the basal ganglia. The nucleus accumbens is associated with the reward system of the brain, showing changes in activity in response to both primary and secondary reinforcers.

object constancy The ability to recognize invariant properties of an object across a wide range of contexts. For example, although the size of the retinal image changes dramatically when a car recedes in the distance, our percept is that the car remains the same size. Similarly, we are able to recognize that an object is the same when seen from different perspectives.

occipital lobe A cortical lobe located at the posterior of the cerebral cortex that primarily contains neurons involved in visual information processing.

odorant A molecule conducted through the air that leads to activation of the olfactory receptors and may be perceived as having a smell when processed through the olfactory system. Compare tastant.

optic ataxia A neurological syndrome in which the patient has great difficulty using visual information to guide her actions, even though she is unimpaired in her ability to recognize objects. Optic ataxia is associated with lesions of the parietal lobe.

optogenetics A procedure in which a genetic manipulation is performed that will result in the expression of a photosensitive protein. The experimenter can then activate the neurons by exposing the tissue to light. The genetic manipulation can be modified such that the protein expression is limited to particular neural regions.

orbitofrontal cortex (OFC) A region of the frontal lobe, located above the orbits of the eyes, that is implicated in a range of functions, including perceptual processes associated with olfaction and taste, as well as those associated with monitoring whether one’s behavior is appropriate.

overt attention Turning one’s head to orient towards a stimulus, be it visual, auditory, olfactory, etc.

P600 response Also syntactic positive shift. A positivepolarity event-related potential elicited when words violate syntactic rules in sentences. Compare N400 response.

parahippocampal place area (PPA) A functionally defined area of the brain (usually with fMRI), located in the parahippocampal region of the temporal lobe that shows a preferential response to stimuli depicting scenes or places.

parietal lobe A cortical lobe located posterior to the central sulcus, anterior to the occipital lobe, and superior to the posterior temporal cortex. This cortical region contains a variety of neurons, including the somatosensory cortex, gustatory cortex, and parietal association cortex, which includes regions involved in visuomotor orienting, attention, and representation of space.

Parkinson’s disease A degenerative disorder of the basal ganglia in which the pathology results from the loss of dopaminergic cells in the substantia nigra. Primary symptoms include difficulty in initiating movement, slowness of movement, poorly articulated speech, and, in some cases, resting tremor. Compare Huntington’s disease.

perceptual representation system (PRS) A form of nondeclarative memory, acting within the perceptual system, in which the structure and form of objects and words can be primed by prior experience and can be revealed later through implicit memory tests.

peripheral nervous system (PNS) A courier network that delivers sensory information to the CNS and then conducts the motor commands of the CNS to control muscles of the body; anything outside the brain and spinal cord. Compare central nervous system.

permeability The extent to which ions can cross a neuronal membrane.

perseveration The tendency to produce a particular response on successive trials, even when the context has changed such that the response is no longer appropriate. Commonly observed in patients with prefrontal damage, perseveration is thought to reflect a loss of inhibitory control.

PET See positron emission tomography.

pharmacological studies Experimental method in which the independent variable involves the administration of a chemical agent or drug. An example would be when people are given drugs that act as dopamine agonists and observations are made on their performance in decision-making tasks.

phoneme The smallest perceived units of sound in a language, of which, for example, there are 40 in the English language.

phonology The way sounds of a language are organized to create meaning.

photoreceptor A specialized cell in the retina that transduces light energy into changes in membrane potential. The photoreceptors are the interface for the visual system between the external world and the nervous system.

phrenology The study of the physical shape of the human head, based on the belief that variations in the skull’s surface can reveal specific intellectual and personality traits. Today phrenology is understood to lack validity.

PiB A radioactive compound that is used as a tracer in PET studies to label beta-amyloid, a substance that is associated with Alzheimer’s Disease. The discovery of PiB provided an important biomarker for identifying people at risk for developing this disease.

pituitary gland Controlled by the hypothalamus, the pituitary gland helps maintain the normal state of the body (homeostasis).

planum temporale The surface area of the temporal lobe that includes Wernicke’s area. The planum temporale has long been believed to be larger in the left hemisphere because of the lateralization of language function, although this theory is currently controversial.

PNS See peripheral nervous system.

pons A region in the brain that includes the pontine tegmental regions on the floor of the fourth ventricle, and the pons itself, a vast system of fiber tracts interspersed with pontine nuclei. The fibers are continuations of the cortical projections to the spinal cord, brainstem, and cerebellar regions. The pons also includes the primary sensory nuclear groups for auditory and vestibular inputs, and somatosensory inputs from, and motor nuclei projecting to, the face and mouth. Neurons of the reticular formation can also be found in the anterior regions of the pons.

population vector A statistical procedure to represent the activity across a group of neurons. Population vectors reflect the aggregate activity across the cells, providing a better correlation with behavior than that obtained from the analysis of individual neurons. For example, the population vector calculated from neurons in the motor cortex can predict the direction of a limb movement.

positron emission tomography (PET) A neuroimaging method that measures metabolic activity or blood flow changes in the brain by monitoring the distribution of a radioactive tracer. The PET scanner measures the photons that are produced during the decay of a tracer. A popular tracer for cognitive neuroscience studies is O15 because its decay time is rapid and the distribution of oxygen increases to neural regions that are active.

posterior commissure Located above the cerebral aqueduct at the junction of the third ventricle, this carries interhemispheric fibers that contribute to the papillary light reflex.

postsynaptic Referring to the neuron located after the synapse with respect to information flow. Compare presynaptic.

prediction error A theoretical construct in theories of reinforcement learning that is defined as the difference between an expected and actual outcome or reward. If the reward is greater than expected, a positive prediction occurs which can be used to increase the likelihood of the behavior. If the reward is less than expected, the negative prediction can be used to decrease the likelihood of the behavior.

preferred direction A property of cells in the motor pathway, referring to the direction of movement that results in the highest firing rate of the neuron. Voxels have also been shown to have preferred directions in fMRI studies, indicating that such preferences can even be measured at the cell population level of analysis.

prefrontal cortex (PFC) A region of cortex that takes part in the higher aspects of motor control and the planning and execution of behavior, perhaps especially tasks that require the integration of information over time and thus mandate the involvement of working memory mechanisms. The prefrontal cortex has three or more main areas that are commonly referred to in descriptions of the gross anatomy of the frontal lobe: the dorsolateral prefrontal cortex, the anterior cingulate and medial frontal regions, and the orbitofrontal cortex.

premotor cortex A secondary motor area that includes the lateral aspect of Brodmann area 6, just anterior to the primary motor cortex. Although some neurons in the premotor cortex project to the corticospinal tract, many terminate on neurons in the primary motor cortex and help shape the forthcoming movement.

presynaptic Referring to the neuron located before the synapse with respect to information flow. Compare postsynaptic.

primary auditory cortex (A1) The initial cortical processing area of the auditory system.

primary gustatory cortex The initial cortical processing area for gustation, located in the insula and operculum.

primary motor cortex (M1) A region of the cerebral cortex that lies along the anterior bank of the central sulcus and precentral gyrus, forming Brodmann area 4. Some axons originating in the primary motor cortex form the majority of the corticospinal tract; others project to cortical and subcortical regions involved in motor control. The primary motor cortex contains a prominent somatotopic representation of the body.

primary olfactory cortex The initial cortical processing area for olfaction, located at the ventral junction of the frontal and temporal cortices, near the limbic cortex.

primary reinforcer A reward or outcome that has a direct benefit for survival. The classic examples are food, water, and sex, since without these, the individual or the species would not survive.

primary somatosensory cortex (S1) The initial cortical processing area for somatosensation, including Brodmann areas 1, 2, and 3. This area of the brain contains a somatotopic representation of the body called the sensory homunculus.

primary visual cortex (V1) The initial cortical processing area for vision, located in the most posterior portion of the occipital lobe, known as Brodmann area 17.

priming A form of learning in which behavior or a physiological response is altered because of some recent stimulus or state. Priming usually refers to changes that occur over a short-time scale; for example, hearing the word “river” primes the word “water.”

procedural memory A form of nondeclarative memory that involves the learning of a variety of motor skills (e.g., knowledge of how to ride a bike) and cognitive skills (e.g., knowledge of how to read).

proprioception The awareness of the position of one’s own body parts, such as limbs. This awareness arises from the information provided by specialized nerve cells at the linkage of the muscles and tendons.

prosopagnosia A neurological syndrome characterized by a deficit in the ability to recognize faces. Some patients will show a selective deficit in face perception, a type of category-specific deficit. In others, the prosopagnosia is one part of a more general agnosia. Prosopagnosia is frequently associated with bilateral lesions in the ventral pathway, although it can also occur with unilateral lesions of the right hemisphere.

PRS See perceptual representation system.

pulvinar A large region of the posterior thalamus comprising many nuclei having interconnections with specific regions of the cortex.

qualia A philosophical term referring to an individual’s personal perception or experience of something.

quantum theory The study of the smallest particles that make up atoms in order to understand the fundamental properties of matter.

rationalism The idea that, through right thinking and rejection of unsupportable or superstitious beliefs, true beliefs can be determined.

rCBF See regional cerebral blood flow.

reappraisal An early cognitive strategy to reassess an emotion.

recency memory Memory for the temporal order of previous events. Recency memory is a form of episodic memory in that it involves remembering when a specific event took place. Patients with prefrontal lesions do poorly on tests of recency memory, even though their long-term memory is relatively intact.

receptive field The area of external space within which a stimulus that must be presented in order to activate a cell. For example, cells in the visual cortex respond to stimuli that appear within a restricted region of space. In addition to spatial position, the cells may be selective to other stimulus features, such as color or shape. Cells in the auditory cortex also have receptive fields. The cell’s firing rate increases when the sound comes from the region of space that defines its receptive field.

reflexive attention The automatic orienting of attention induced by bottom-up, or stimulus-driven, effects, such as when a flash of light in the periphery captures one’s attention. Compare voluntary attention.

reflexive cuing See exogenous cuing.

refractory period The short period of time following an action potential during which the neuron may not be able to generate action potentials or may be able to do so only with larger-than-normal depolarizing currents.

regional cerebral blood flow (rCBF) The distribution of the brain’s blood supply, which can be measured with various imaging techniques. In PET scanning, rCBF is used as a measure of metabolic changes following increased neural activity in restricted regions of the brain.

relational memory Memory that relates the individual pieces of information relevant to a particular memory and that supports episodic memories.

repetition suppression effect The phenomenon seen during functional MRI in which the BOLD response to a stimulus decreases with each subsequent stimulus repetition.

response conflict A situation in which more than one response is activated, usually because of some ambiguity in the stimulus information. It has been hypothesized that the anterior cingulate monitors the level of response conflict and modulates processing in active systems when conflict is high.

resting membrane potential The difference in voltage across the neuronal membrane at rest, when the neuron is not signaling.

restorative justice An attempt to restore the harm done by involving the perpetrator, the victim and the community in the resolution.

retina A layer of neurons along the back surface of the eye. The retina contains a variety of cells, including photoreceptors (the cells that respond to light) and ganglion cells (the cells whose axons form the optic nerve).

retinotopic Referring to a topographic map of visual space across a restricted region of the brain. Activation across the retina is determined by the reflectance of light from the environment. A retinotopic map in the brain is a representation in which some sort of orderly spatial relationship is maintained. Multiple retinotopic maps have been identified in the cortex and subcortex.

retinotopic map A topographic representation in the nervous system that reflects spatial properties of the environment in an eye-based reference frame. For example, primary visual cortex contains a retinotopic map of the contralateral side of space, relative to the center of gaze.

retributive justice Justice that imposes punishment commiserate with the magnitude of the crime as the best response to a crime.

retrieval The utilization of stored information to create a conscious representation or to execute a learned behavior like a motor act. Compare encoding.

retrograde amnesia The loss of memory for events that happened in the past. Compare anterograde amnesia.

Ribot’s Law See temporal gradient.

reversal learning An attempt to teach someone to respond in the opposite way in which they were previously taught.

S1 See primary somatosensory cortex.

S2 See secondary somatosensory cortex.

saltatory conduction The mode of conduction in myelinated neurons, in which action potentials are generated down the axon only at nodes of Ranvier. Measurement of the propagation of the action potential gives it the appearance of jumping from node to node—hence the term saltatory, which comes from the Latin saltare, meaning “to jump.”

SAS See supervisory attentional system.

scotoma A region in external space in which a person or animal fails to perceive a stimulus following neural damage. Scotomas occur following lesions of primary visual cortex or partial lesions of ascending visual pathways. The size and location of scotomas vary depending on the extent and location of the lesions.

secondary reinforcer Rewards that do not have intrinsic, or direct value, but have acquired their desirability as part of social and cultural norms. Money and social status are important secondary reinforcers.

secondary somatosensory cortex (S2) The area of the brain that receives inputs from primary somatosensory cortex and processes higher level somatosensory information.

selective attention The ability to focus one’s concentration on a subset of sensory inputs, trains of thought, or actions, while simultaneously ignoring others. Selective attention can be distinguished from nonselective attention, which includes simple behavioral arousal (i.e., being generally more versus less attentive).

self-knowledge A philosophical term referring to an individual’s knowledge of their own personal nature such as beliefs, abilities and desires.

self-reference effect An effect rooted in the theoretical perspective that the recall of information is related to how deeply the information was initially processed. Specifically, the self-reference effect is the superior memory for information that is encoded in relation to oneself.

semantic The way that meaning is represented in the words of a language.

semantic memory Knowledge that is based on facts one has learned, but does not include knowledge of the context in which the learning occurred. A form of declarative memory. Contrast with episodic memory.

semantic paraphasia The production of a word related in meaning to the intended word (e.g., horse for cow) instead of the intended word itself. Wernicke’s aphasia patients often produce semantic paraphasias.

sensorimotor adaptation A form of motor learning in which a learned skill is modified due to some change in the environment or agent. For example, a soccer player who adjusts her shot to compensate for a strong cross-wind is exhibiting a form of motor adaptation.

sensorimotor learning A term that refers to the acquisition of a new motor skill or capability. Motor learning can arise from maturation processes (e.g, infants crawling) or intense, dedicated practice (e.g, piano playing).

sensory memory The short-lived retention of sensory information, measurable in milliseconds to seconds, as when we recover what was said to us a moment before when we were not paying close attention to the speaker. Sensory memory for audition is called echoic memory; sensory memory for vision is called iconic memory. Compare short-term memory and long-term memory.

sentience The ability to be conscious and experience subjectivity.

short-term memory The retention of information over seconds to minutes. See also working memory. Compare long-term memory and sensory memory.

simulation A method used in computer modeling to mimic a certain behavior or process. Simulations require a program that explicitly specifies the manner in which information is represented and processed. The resulting model can be tested to see if its output matches the simulated behavior or process. The program can then be used to generate new predictions.

simulation theory A theoretical account of how we understand other people’s minds. From this perspective, we try to make inferences about other people’s minds by considering what we might do if we were in their position.

single-cell recording A neurophysiological method used to monitor the activity of individual neurons. The procedure requires positioning a small recording electrode either inside a cell or, more typically, near the outer membrane of a neuron. The electrode measures changes in the membrane potential and can be used to determine the conditions that cause the cell to respond.

single dissociation A method used to develop functional models of mental and/or neural processes. Evidence of a single dissociation requires a minimum of two groups and two tasks. A single dissociation is present when the groups differ in their performance on one task but not the other. Single dissociations provide weak evidence of functional specialization since it is possible that the two tasks differ in terms of their sensitivity to detect group differences. Compare double dissociation.

SMA See supplementary motor area.

smoothing Data processing technique used in functional imaging studies. Given that the signal being measured in small, relative to the noise (random variation), signal processing techniques provide a more robust measure by performing a weighted average of the signal from the observed location with its spatial neighbors.

social cognitive neuroscience An emerging field of brain science that combines social-personality psychology and cognitive neuroscience with the goal of understanding the neural mechanisms involved in social interaction in humans.

soma (pl. somata) The cell body of a neuron.

somatic marker A physiological-emotional mechanism that was once theorized to help us sort through possible options and make a decision. Somatic markers were thought to provide a common metric for evaluating options with respect to their potential benefit.

somatotopy A point-for-point representation of the body surface in the nervous system. In the somatosensory cortex, regions of the body near one another (e.g., the index and middle fingers) are represented by neurons located near one another. Regions that are farther apart on the body surface (e.g., the nose and the big toe) are coded by neurons located farther apart in the somatosensory cortex.

spike-triggering zone The location, at the juncture of the soma and the axon of a neuron, where currents from synaptic inputs on the soma and distant dendrites are summed and where voltage-gated Na+ channels are located that can be triggered to generate action potentials that can propagate down the axon.

spinal interneurons A neuron found in the spinal cord. Many descending axons from the pyramidal and extrapyramidal tracts synapse on interneurons which, in turn, synapse on other interneurons or alpha motorneurons.

spine A little knob attached by a small neck to the surface of a dendrite. Synapses are located on spines.

splenium The posterior area of the corpus callosum that interconnects the occipital lobe.

split-brain research The study of patients who have had the corpus callosum severed, typically as a radical treatment for intractable epilepsy.

stimulus-driven Describing behavior that is dictated by the environmental context and fails to incorporate an animal’s or person’s goals. For example, a person with a lesion of prefrontal cortex might drink from a glass placed in front of him even if he isn’t thirsty.

storage The result of the acquisition and consolidation of information, which create and maintain, respectively, a permanent record.

striatum One of the nuclei of the basal ganglia. The striatum is the main receiving zone of the basal ganglia, receiving extensive inputs from the cerebral cortex and other subcortical structures. The striatum in humans is composed of the caudate and putamen nuclei.

stimulus–response decision Behavior in which the response is tightly linked to the stimulus, usually through extensive experience. See also habit.

subliminal perception When a stimulus, which is not consciously perceived, nevertheless influences one’s conscious state.

substantia nigra One of the nuclei that form the basal ganglia. The substantia nigra is composed of two parts: The axons of the substantia nigra pars compacta provide the primary source of the neurotransmitter dopamine and terminate in the striatum (caudate and putamen). The substantia nigra pars reticularis is one of the output nuclei from the basal ganglia.

sulcus (pl. sulci) Also fissure. An invaginated region that appears as a line or crease of the surface of the cerebral cortex. Compare gyrus.

superior colliculus A subcortical visual structure located in the midbrain. The superior colliculus receives input from the retinal system and is interconnected with the subcortical and cortical systems. It plays a key role in visuomotor processes and may be involved in the inhibitory component of reflexive attentional orienting. Compare inferior colliculus.

supervisory attentional system (SAS) The psychological model used to explain how response selection is achieved in a flexible manner. Without the SAS, behavior is dictated by context, with the selected action being the one that has been produced most often in the current context. The SAS allows for flexible behavior by biasing certain actions based on current goals or helping to determine actions in unfamiliar situations.

supplementary motor area (SMA) A secondary motor area that includes the medial aspect of Brodmann area 6, just anterior to the primary motor cortex. The SMA plays an important role in the production of sequential movements, especially those that have been well learned.

suppression Intentionally excluding a thought or feeling from conscious awareness.

Sylvian (lateral) fissure Also lateral fissure. A large fissure (sulcus) on the lateral surface of the cerebral cortex first described by the anatomist Franciscus Sylvius. The Sylvian fissure separates the frontal cortex from the temporal lobe below.

symmetry breaking A term in physics, which describes the phenomenon that occurs when small fluctuations acting on a system at a critical point determine which of several equally likely outcomes will occur.

synapse The specialized site on the neural membrane where a neuron comes in close position to another neuron to transmit information. Synapses include both presynaptic (e.g., synaptic vesicles with neurotransmitter) and postsynaptic (e.g., receptors) specializations in the neurons that are involved in chemical transmission. Electrical synapses involve special structures called gap junctions that make direct cytoplasmic connections between neurons.

synapse elimination The elimination of some synaptic contacts between neurons during development, including postnatally.

synaptic cleft The gap between neurons at synapses.

synaptic potential The voltage difference across the membrane at the synapse during synaptic transmission.

synaptogenesis The formation of synaptic connections between neurons in the developing nervous system.

syncytium (pl. syncytia) A continuous mass of tissue that shares a common cytoplasm.

synesthesia A mixing of the senses whereby stimulation of one sense (e.g., touch) automatically causes an illusory perceptual experience in the same or another sense (e.g., vision).

syntactic parsing The assignment of a syntactic structure to a word in a sentence (e.g., this word is the object of the sentence, and this word is the action).

syntax The rules that constrain word combinations and sequences in a sentence.

Talairach coordinate An anatomical referencing system in which a brain location is defined in three spatial dimensions (x,y,z). The Talairach atlas was devised from the detailed analysis of one human brain and has been used to provide a reference for comparing across individuals in neuroimaging studies.

tastant A food molecule that stimulates a receptor in a taste cell to initiate the sensory transduction of gustation. Compare odorant.

temporal gradient The effect in which some cases of retrograde amnesia tend to be greatest for the most recent events.

temporal lobe Lateral ventral portions of the cerebral cortex bounded superiorly by the Sylvian fissure and posteriorly by the anterior edge of the occipital lobe and ventral portion of the parietal lobe. The ventromedial portions contain the hippocampal complex and amygdala. The lateral neocortical regions are involved in higher order vision (object analysis), the representation of conceptual information about the visual world, and linguistic representations. The superior portions within the depths of the Sylvian fissure contain auditory cortex.

temporally limited amnesia Retrograde amesia following brain damage that extents backwards from the time of the damage, but does not include the entire life of the individual.

thalamic reticular nucleus (TRN) A thin layer of neurons surrounding the nuclei of the thalamus, which receives inputs from the cortex and subcortical structures and sends projections to the thalamic relay nuclei.

thalamus A group of nuclei, primarily major sensory relay nuclei for somatosensory, gustatory, auditory, visual, and vestibular inputs to the cerebral cortex. The thalamus also contains nuclei involved in basal ganglia–cortical loops, and other specialized nuclear groups. It is a part of the diencephalon, a subcortical region, located in the center of the mass of the forebrain. Each hemisphere contains one thalamus, and they are connected at the midline in most humans by the massa intermedia.

theory of mind Also mentalizing. The ability to self-reflect and think about the mental states of others, which allows predictions of what others can understand, and how they will interact and behave in a given situation. This trait is considered unique to the human species.

theory theory A scientific theory where one makes an assessment of other’s mental states based on their own theories of the outside world.

threshold The membrane potential value to which the membrane must be depolarized for an action potential to be initiated.

time-frequency analysis Signal processing technique for analyzing the content of a stimulus and how that content changes over time. For example, in ECoG, a time frequency analysis describes the power of the neural activity at different frequencies over time.

TMS See transcranial magnetic stimulation.

topography The systematic relationship between a particular property of the external world and the neural representation of that property. Examples of topographic representations include retinotopic maps in the visual cortex, tonotopic maps in the auditory cortex, and somatosensory maps in the motor and sensory cortices.

tract A bundle of axons in the central nervous system.

transcortical Pertaining to communication between locations in the cortex. For example, transcortical fibers connect the frontal cortex to the temporal cortex.

transcranial direct current stimulation (tDCS) A noninvasive method in which a low voltage electrical current is created across the brain by applying two electrodes to the scalp. tDCS is hypothesized to potentiate neurons near the anodal electrode and hyperpolarize neurons near the cathodal electrode.

transcranial magnetic stimulation (TMS) A noninvasive method used to stimulate neurons in the intact human brain. A strong electrical current is rapidly generated in a coil placed over the targeted region. This current generates a magnetic field that causes the neurons in the underlying region to discharge. TMS is used in clinical settings to evaluate motor function by direct stimulation of the motor cortex. Experimentally, the procedure is used to transiently disrupt neural processing, thus creating brief, reversible lesions.

transient global amnesia A sudden, dramatic, but transient (lasting only hours) amnesia that is both anterograde and retrograde.

traumatic brain injury (TBI) A form of brain injury resulting from an accident such as a diving accident, bullet wound, or blast injury. The damage in TBI is usually diffuse with damage to both grey and white matter tracts from the accelerative forces experienced at the time of the injury.

unilateral spatial neglect Also simply neglect. A behavioral pattern exhibited by neurological patients with lesions to the forebrain, in which they fail at or are slowed in acknowledging that objects or events exist in the hemispace opposite their lesion. Neglect is most closely associated with damage to the right parietal cortex.

utilitarian justice Also known as consequentialism, is justice that is forward looking and is concerned about the greater future good for society. This may or may not involve punishment, deterrence, incapacitation, rehabilitation, and may or may not be “fair.”

utilization behavior An extreme dependency on the prototypical use of an object without regard for its use in a particular context.

V1 See primary visual cortex.

value An abstract entity referring to the overall preference given to a stimulus or action. The value is assumed to reflect the combination of a number of different attributes such as how much reward will be received, the likelihood of that reward, and the efforts and costs required to achieve the reward.

ventral (occipitotemporal) stream The visual pathway that traverses the occipital and temporal lobes. This pathway is associated with object recognition and visual memory.

ventral tegmental area A part of the dopamine system. Dopaminergic neurons originating here project through either the mesolimbic pathway, or the mesocortical pathway.

vesicle A small intracellular organelle, located in the presynaptic terminals at synapses, that contains neurotransmitter.

view-dependent frame of reference A theory based on the idea that perception involves recognizing an object from a certain viewpoint. View-dependent theories assume that visual memory is based on previous experiences with objects in specific orientations and that the recognition of an object in a novel orientation involves an approximation process to the stored representations of specific perspectives. Compare view-invariant frame of reference.

view-invariant frame of reference A theory based on the idea that perception involves recognizing certain properties of an object that remain invariant, or constant across different perspectives. In this view, these properties form the basis of visual memory, and recognition entails matching the perceived properties to this knowledge base. Compare view-dependent frame of reference.

visual agnosia A failure of perception that is limited to the visual modality. In visual agnosia, the patient is relatively good at perceiving properties such as color, shape, or motion yet cannot recognize objects or identify their uses.

visuomotor adaptation A form of sensorimotor adaptation in which the visual feedback is altered, resulting in a mismatch between proprioception and vision. With practice, the motor system adjusts to compensate for the mismatch.

voltage-gated ion channel A transmembrane ion channel that changes molecular conformation when the membrane potential changes, changing the conductance of the channel for specific ions such as sodium, potassium or chloride.

voluntary attention The volitional, or intentional, focusing of attention on a source of input, train of thought, or action. Compare reflexive attention.

voxel The smallest unit of three-dimensional data that can be represented in an MRI.

Wada test A clinical procedure in which a barbituate is injected to temporarily disrupt function in one of the cerebral hemispheres. This procedure, used to identify the source of epileptic seizures provided important initial insights into hemispheric specialization.

Wernicke’s aphasia A language deficit usually caused by brain lesions in the posterior parts of the left hemisphere, resulting in comprehension deficits. Compare Broca’s aphasia.

Wernicke’s area Area of human left posterior superior temporal gyrus: Identified by Carl Wernicke in the 19th century.

white matter Regions of the nervous system composed of millions of individual axons, each surrounded by myelin. The myelin is what gives the fibers their whitish color—hence the name white matter. Compare gray matter.

working memory Transient representations of task-relevant information. These representations may be related to information that has just been activated from long-term memory or something recently experienced. Representations in working memory guide behavior in the present, constituting what has been called, “the blackboard of the mind.” See also short-term memory.