Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory

Abstract

Caffeine, the world's most common psychoactive substance, is used by approximately 90% of North Americans everyday. Little is known, however, about its benefits for memory. Napping has been shown to increase alertness and promote learning on some memory tasks. We directly compared caffeine (200mg) with napping (60-90 minutes) and placebo on three distinct memory processes: declarative verbal memory, procedural motor skills, and perceptual learning. In the verbal task, recall and recognition for unassociated words were tested after a 7hr retention period (with a betweensession nap or drug intervention). A second, different, word list was administered post-intervention and memory was tested after a 20min retention period. The non-declarative tasks (finger tapping task and texture discrimination task) were trained before the intervention and then retested afterwards. Naps enhanced recall of words after a 7hr and 20min retention interval relative to both caffeine and placebo. Caffeine significantly impaired motor learning compared to placebo and naps. Napping produced robust perceptual learning compared with placebo; however, naps and caffeine were not significantly different. These findings provide evidence of the limited benefits of caffeine for memory improvement compared with napping. We hypothesize that impairment from caffeine may be restricted to tasks that contain explicit information; whereas strictly implicit learning is less compromised.

REM, not incubation, improves creativity by priming associative networks

“…While controlling for circadian effects, the present study found that sleep specifically enhanced the associative network for primed solutions but did not improve memory consolidation. Although other studies have reported that sleep enhances explicit verbal memory (22,35), our memory measures were not comparable with these recall tasks because exposure to the verbal material was primed and not explicitly presented. Furthermore, not only were NREM sleep, REM sleep, and quiet rest groups indistinguishable on the memory measures, performance on these memory measures was not correlated with performance on the primed RAT items.…”

“…Because daytime sleep has been shown to increase alertness and improve a range of cognitive functions (perceptual, verbal, and motor learning; declarative and implicit memory) (18,(21)(22)(23)(24), we tested whether sleep or quiet rest might enhance general creativity on new RAT items. Baseline assessments were measured on the morning RAT.…”

The effect of caffeine on working memory load-related brain activation in middle-aged males

“…The Karolinska sleepiness scale (KSS) was administered as a measure of subjective feelings of sleepiness/alertness (1 = very alert, 9 = very sleepy) (Akerstedt and Gillberg, 1990), with demonstrated sensitivity to caffeine effects (Mednick et al, 2008). The Dutch short visual analogue scale (VAS) version of the Profile of Mood States (POMS) (Wald and Mellenbergh, 1990) was administered; the fatigue (6 items: 0 = low fatigue, 100 = high fatigue) and vigour (5 items: 0 = low vigour, 100 = high vigour) subscales are recommended measures of the mood of energy and fatigue in investigations that are short in duration (O'Connor, 2006) and the vigour scale has shown sensitivity to caffeine effects (Childs and de Wit, 2008;Herz, 1999).…”

Napping During Night Shift: Practices, Preferences, and Perceptions of Critical Care and Emergency Department Nurses

“…A growing body of literature in areas outside of health care supports the concept that vigilance 45 and memory 46,47 are improved when workers are allowed to nap. Several studies support positive outcomes for on-duty napping by health professionals.…”