Abstract
Naps enhance a wide range of learning, including visual perceptual, motor and declarative memory. However, napping is not as common a sleepiness-countermeasure as caffeine and modafinil. The extent to which these wakefulness promoters produce benefits equal to napping is unknown. In a double-blind study, we compared the effects of a 60–90min nap to 200mg of caffeine, 100mg of modafinil, and placebo on four different memory processes. 46 healthy volunteers were tested on four different types of learning: 1) perceptual: Texture Discrimination Task (TDT), visuospatial: Rey-Osterreith Complex Figure (RO) 2) motor: Finger Tapping Task (FTT), 3) declarative: Verbal Learning Task (VL). The first test session was at 9AM. At 12:30, all subjects were fitted with polysomnography monitors. Starting at 1PM, nappers slept up to 90 minutes but stayed in bed no later than 3PM, while non-nappers listened to a book on tape. Pills were administered at 2:30PM. Vitals signs were measured every half hour. At 3PM, all subjects retested. Task order was randomized across subjects, and each test session lasted 2 hours. Group differences were found on the four memory tasks. TDT: nappers showed improvement, there was no change in either drug group, and performance deteriorated in the placebo group. RO: nappers and modafinil groups showed improved visuospatial memory. FTT: The caffeine and modafinil groups showed slowed response times. HVLT: the modafinil group showed increased delayed recall, whereas the caffeine group showed decreases in most measures of declarative memory; nappers and placebo showed no change. We found differential memory enhancement and deterioration with the administration of a nap, caffeine and modafinil. Perceptual learning required a nap. Motor learning deteriorated with pharmacological intervention. Visuospatial memory improved with naps and modafinil. Declarative memory improved with naps and modafinil. These results have important implications for sustained performance applications in civilian and military operations.