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Alexandra Thomson

Sleep Loss and Temporal Memory. Alexandra Thomson. Y. Harrison & J.A. Horne. Introduction. Other tests have used sleep-deprived volunteers that are previously well trained in the task procedure  minimize “practice effects”

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Alexandra Thomson

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  1. Sleep Loss and Temporal Memory Alexandra Thomson Y. Harrison & J.A. Horne

  2. Introduction • Other tests have used sleep-deprived volunteers that are previously well trained in the task procedure  minimize “practice effects” • Failed to consider that eventually the task becomes uninteresting  Boredom (Kjellberg, 1977; Wilkinson, 1961)

  3. Introduction • Therefore, Harrison and Horne attempted to reduce boredom and sleepiness to specifically examine sleep loss effects on cognitive processes associated with temporal memory

  4. Research Question • Does sleep deprivation have an effect on temporal memory? • Note: Temporal memory = memory for when events occur (eg. recency of presentation)

  5. Methods

  6. Participants • 40 individuals • 20 males, 20 females • Mean age 23.4 years (range 18-34 years old) • Non-smokers, not heavy drinkers • No sleep or medical problems • Moderate caffeine drinkers (100-400 mg /day)

  7. Randomly Assigned Groups Control Groups Experimental Groups Sleep-Deprived plus Placebo Sleep-Deprived plus Caffeine • Non-Sleep-Deprived plus Placebo • Non-Sleep-Deprived plus Caffeine

  8. Sleep • Sleep was monitored by actimeter • Sleep deprivation groups stayed in lab overnight and were monitored by two assistants  no sleeping

  9. Caffeine or Decaf • 350 mg anhydrous caffeine dissolved in 200mL decaffeinated coffee in 2 doses for caffeine groups • Placebo groups had decaffeinated coffee

  10. Time of Testing • Tested between 19:30 hr and 20:30 hr on the second day (ie. After 35 hour sleep deprivation for sleep deprivation groups) • Circadian acrophase: feel most alert

  11. Tasks • Coloured photographs of unfamiliar faces. • List A and B, each containing 12 faces. Shown sequentially, one every 10 s. • Self-ordered pointing task (distraction/way to occupy them in a standard way) during interim period that lasted 5 minutes • 48 faces shown (including 24 from list A and B).

  12. Questions • Seen face before ?  recognition memory • If yes, from list A or list B ?  recency discrimination (ie. Temporal memory)

  13. Confidence Judgements • Ratings separated for right and wrong responses (“accuracy”) • 5-point scale • 5= 100% certain (that I am correct) • 4= Very certain • 3= Quite certain • 2= Not very certain • 1= Just guessing

  14. Subjective Sleepiness • Karolinska Sleepiness Scale (9-point scale) • 9= Very sleepy, great effort to keep awake, fighting sleep • 8= Sleepy, some effort to stay awake • 7= Sleepy, no effort to stay awake • 6= Some signs of sleepiness • 5= Neither alert nor sleepy • 4= Some signs of alertness • 3= Alert • 2= Very alert • 1= Extremely alert

  15. Results

  16. Results • Sleep-deprived caffeine group was significantly less sleepy (ie. More alert) than the sleep-deprived placebo group.

  17. Figure 1. Mean subjective sleepiness (Karolinska Sleepiness Scale) scores throughout day 2 for SDc and SDp

  18. Figure 2. Mean and standard deviation for d’ (recognition). Mean and standard deviation for z sensitivity (recency)

  19. Results Recognition Recency High scores indicate good performance Sleep deprivation significantly impaired temporal memory Sleep-deprived group with caffeine scored higher than sleep-deprived placebo group Non-sleep-deprived groups did the best • High scores indicate a high level of hits with low false positives • Sleep deprivation did not have a significant effect

  20. Confidence and Accuracy • Sleep deprivation increased belief that they were correct • Especially when they were wrong • Caffeine had no significant effect on confidence judgements

  21. Discussion • Optimum performance circumstances (novel test, short, circadian acrophase, caffeine)  still significant impairment of temporal memory • Research has shown that temporal memory depends on pre-frontal cortex (lesion studies and patients with damaged pre-frontal cortex  poor recency discrimination, no effect on recognition) • Daum, Graber, Schugens, and Mayes (1996), McIntosh, Grady, Haxby, Ungerleider, and Horwitz (1996); Milner, Corsi, and Leonard, (1991) • Do the present findings indicate that sleep deprivation affects prefrontal cortex ?

  22. My Opinion Strengths/Pros Limitations/Cons Small sample size (5 females and 5 males per group) No brain scans, lacking visuals Didn’t show results of actimeter Unclear if effects of sleep deprivation specifically relates to temporal memory • Placebo and caffeine given double blind • Equal number of males and females in each of the 4 groups • Tried to reduce boredom as much as possible to ensure results were due to sleep deprivation on temporal memory • Easy to read, no jargon • Broken up into clear sections

  23. Future Research • Use higher doses of caffeine to see if the adverse effects of sleep deprivation on temporal memory could be eliminated • Investigate if there is a dose-response relationship • Do the effects relate to a more general problem with source memory? • Need to look at other aspects of the encoding stage (if and when)

  24. Questions

  25. Harrison, Y. & Horne J.A. (2000). Sleep Loss and Temporal Memory. The Quarterly Journal of Experimental Psychology, 1, 271-279. Full Citation

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