Sleep Deprivation History and Memory Consolidation

1. Sleep Deprivation History and Memory Consolidation Mikiko Fujiwara MCB 186

2. Introduction • Memory is improved in a sleep-dependent manner • Motor skills and memory: possible improvement in stage 2 sleep • Sleep deprivation reduces overall alertness, reaction time, and causes many physiological changes in sleep profile • To date, most studies on sleep-dependent motor skill enhancement do not explore sleep deprivation effects on learning

3. Problems • Does prior sleep history affect learning? • How does prior sleep history affect memory consolidation? • Does the second night of sleep always improve learning equally?

4. Hypothesis • Learning ability will correlate with amount of sleep obtained • Performance improvement due to post training sleep will correlate with amount of sleep obtained, but will also plateau at ~9h of sleep.

5. Methods • 120 healthy volunteers, age 18-30, screened for sleep disorders and substance abuse, little to mild caffeine usage, normal sleep schedules • split into 6 groups of 20 • Sleep 8-9 h for 2 weeks at home; confirmed using sleep logs/actigraphy watches • First night in lab: groups sleep 4, 6, 8, 9, 10, 12h • Subjects trained every 3h starting 1h post wake • Evaluated on task 1h before sleep. • Second night in lab: All groups sleep for 8.5h • Evaluated on task 1, 4, and 7h post wake.

6. Methods (Cont.) • Sequential finger-tapping task: • Subjects asked to type 4-6-1-7-3-2-5-7-4 using standard PC keyboard repeatedly and as quickly as possible for 30s period • Sequence always displayed, white dots indicate typed number • Training: 12 30s trials with 30s rest period • Averages of trials taken for each evaluation.

7. Expected Results

8. Significance of Results • Day 1: zero, equal, or gradated improvement? • Day 2: equal or gradated improvement? • Factors involved: preoccupation with sleep debt recovery-->differing stages of sleep • Too much of a good thing? • Implications for sensitive hands-on learning (i.e., surgery, operating machinery/vehicles, music) • Further insight into memory consolidation and learning

9. Future Directions • Explorations of mechanisms behind memory consolidation of motor skills --> Ach involvement? • Similar effects in other types of learning? (i.e., visual, auditory, perceptive, etc.) • EEG or MRI study on motor skill improvement with sleep deprivation

10. Acknowledgements • Profs. C.A.Czeisler and J.W.Hastings • Dr. J.J.Gooley • MCB 186 classmates

11. References • S. Fischer, M.Hallschmid, A.L.Elsner, and J. Born. Sleep forms memory for finger skills. 2002 99:18: 11987–11991 PNAS. • K. Kuriyama, R. Stickgold, and M.P. Walker. Sleep-dependent learning and motor-skill complexity. 2004 11: 705-713 Learn. Mem. • M.E. Smith, L.K. McEvoy, A.Gevins. The Impact of Moderate Sleep Loss on Neurophysiologic Signals during Working-Memory Task Performance. Sleep. 2002 November 1; 25(7): 784–794. • R. Stickgold. Sleep-dependent memory consolidation. 2005 437: 1272-1278 Nature. • M.P. Walker, T.Brakefield, J.Seidman, A.Morgan, J.A.Hobson and R.Stickgold. Sleep and the Time Course of Motor Skill Learning. 2003 10: 275-284 Learn. Mem.