66. Not until recently did scientists find out that ____.

1. new neurons could grow in adult brains
2. neurons could be man-made in the laboratory
3. neurons were destroyed in Alzheimer's disease
4. humans could produce new neurons as animals

67. Gould's notion was that the short-lived neurons ____.

1. did survive longer than expected
2. would die much sooner than expected could
3. could actually better learning and memory
4. could be kept alive by stimulating the hippocampus

68. Which of the following can clearly tell the two groups of rats from each other in the test?

1. The water used.
2. The noises played.
3. The neurons newly born.
4. The hippocampus involved.

69. Gould theorizes that the Salk group's failure to report the same results was due to ____.

1. the timing of labeling new neurons
2. the frequency of stimulation
3. the wrongly labeled neurons
4. the types of learning tasks

70. Which of the following can be the best title for the passage?

1. Use It or Lose It
2. Learn to Survive
3. To Be or Not to Be
4. Stay Mentally Healthy

(Reference keys.)