Y. Harrison & J.A. Horne A LEXANDRA T HOMSON

I NTRODUCTION  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)

I NTRODUCTION  Therefore, Harrison and Horne attempted to reduce boredom and sleepiness to specifically examine sleep loss effects on cognitive processes associated with temporal memory

R ESEARCH Q UESTION  Does sleep deprivation have an effect on temporal memory?  Note: Temporal memory = memory for when events occur (eg. recency of presentation)

M ETHODS

P ARTICIPANTS  40 individuals  20 males, 20 females  Mean age 23.4 years (range years old)  Non-smokers, not heavy drinkers  No sleep or medical problems  Moderate caffeine drinkers ( mg /day)

R ANDOMLY A SSIGNED G ROUPS Control Groups  Non-Sleep- Deprived plus Placebo  Non-Sleep- Deprived plus Caffeine Experimental Groups  Sleep-Deprived plus Placebo  Sleep-Deprived plus Caffeine

S LEEP  Sleep was monitored by actimeter  Sleep deprivation groups stayed in lab overnight and were monitored by two assistants  no sleeping

C AFFEINE OR D ECAF  350 mg anhydrous caffeine dissolved in 200mL decaffeinated coffee in 2 doses for caffeine groups  Placebo groups had decaffeinated coffee

T IME OF T ESTING  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

T ASKS  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).

Q UESTIONS  Seen face before ?  recognition memory  If yes, from list A or list B ?  recency discrimination (ie. Temporal memory)

C ONFIDENCE J UDGEMENTS  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

S UBJECTIVE S LEEPINESS  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

R ESULTS

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

F IGURE 1. M EAN SUBJECTIVE SLEEPINESS (K AROLINSKA S LEEPINESS S CALE ) SCORES THROUGHOUT DAY 2 FOR SD C AND SD P

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

R ESULTS Recognition  High scores indicate a high level of hits with low false positives  Sleep deprivation did not have a significant effect 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

C ONFIDENCE AND A CCURACY  Sleep deprivation  increased belief that they were correct  Especially when they were wrong  Caffeine had no significant effect on confidence judgements

D ISCUSSION  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 ?

M Y O PINION Strengths/Pros  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 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

F UTURE R ESEARCH  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)

Q UESTIONS

F ULL C ITATION Harrison, Y. & Horne J.A. (2000). Sleep Loss and Temporal Memory. The Quarterly Journal of Experimental Psychology, 1,