1. Drummon, S. P. A., Brown, G. G., Gillin, J. C., Stricker, J. L., Wong, E. C., Buxton, R. B. Lecturer: Katie Yan

2. Introduction  Sleep Deprivation (SD) = lack of sleep Study specifies ~35 hours awake  One night’s sleep deprivation impairs performance on many cognitive tasks Especially verbal learning & tasks dependent upon Pre-Frontal Cortex (PFC) involvement  Associated with impairments in the cerebral systems that form the neural substrates of these functions  Effects are poorly understood

3. Variables DependentIndependent  Performance on verbal learning tasks  Brain areas activated  Rested State  Sleep-Deprived State

4. Hypothesis  Sleep Deprivation will significantly impair free recall. On the basis of previous studies, they predicted that PFC would be less responsive to cognitive demands following SD.

5. Methods Participants:  13 normal healthy young adults Relatively normal sleeping patterns  During SD: Monitored in a hospital from 22:00 until time of scan around 16:30-18:00 the next day ○ 34.7 ± 1.2 hours without sleep Not allowed stimulants of any kind

6. Methods Design:  Five baseline & four experimental blocks alternating Each block 40s; total trial 360s

7. Methods  Baseline Five words were presented & instructed to not memorize but to determine whether UPPER or lower-case letters.  Experimental Instructed to memorized the five words for later testing Tested ~10min after the end of functional scans

8. Methods Procedures:  The order of rested and SD conditions was counterbalanced: Four separate cognitive tasks during fMRI scans in both states Serial subtraction for analysis ○ 20 sagittally oriented slices covering whole brain ○ Identified regions that were significantly more activated during one state than the other

9. Results Subjects performed significantly less well on free recall when they were sleep-deprived.

10. Results Subjects did not perform significantly differently between Rested state and SD state in recognition tasks.

11. Results  The PFC was more responsive after one night of sleep deprivation than after normal sleep, contrary to the hypothesis. Increased subjective sleepiness in sleep- deprived subjects correlated significantly with activation of the PFC.

12. Temporal lobes were significantly more activated during rested state than during SD. The bilateral parietal lobes and two additional frontal regions were more activated after SD than rested state.

13. Results Although sleep deprivation significantly impaired free recall compared with the rested state, better free recall in sleep- deprived subjects was associated with greater parietal lobe activation. ○ Measured through haemodynamic responses

14. Discussion Regarding the Parietal Lobe:  Following SD, activation within the parietal lobes was related to preservation of near-normal verbal learning  Neurophysiological substrate of the initial compensation for SD  Underlie partially successful behaviour adaptation to SD during verbal learning  Restricted to certain cognitive functions

15. Discussion Regarding the Temporal Lobe:  Behavioural compensation for SD was not complete, and some of the changes in cerebral activation that followed SD may have contributed to poorer recall performance.  Reduced response of the left temporal lobe to verbal learning Lowered free recall scores?

16. Personal Opinions...  Considered that simple repetition of verbal learning task might alter BOLD response through practice effects or habituation. Used t-test to compare 1 st & 2 nd nights of activation to look for significant alterations of BOLD response No overlap! Strengths:

17. Personal Opinions...  Only had 13 subjects Gender was also not specified  Tasks consisted of only five words Too little?  Relatively short duration of sleep deprivation May have only measured period of time when brain is still able to compensate for SD and maintain relatively intact performance Limitations

18. Personal Opinions...  If they achieved longer sleep deprivation, they may have observed a smaller compensatory response, or even something novel. Try it!  Decreased temporal activity in Alzheimer’s Alzheimer patients as subjects! Future Possibilities:

19. Take Home Message: Only pull all-nighters for multiple choice final exams, don’t bother for short answer exams... You will probably fail. You will probably fail.

20. Les Questions?