Aging and Alzheimer's disease (AD) are both characterized by memory impairments and sleep changes. We investigated the potential link between these disturbances, focusing on sleep spindles, involved in memory consolidation. Two episodic memory tasks were given to young and old healthy participants, as well as to AD patients. Postlearning sleep was recorded. Sleep spindles were globally reduced in aging and AD. AD patients also exhibited a further decrease in fast spindles. Besides, mean intensity of fast spindles was positively correlated, in AD patients, with immediate recall performance. Our results are the first report of a specific decrease in fast spindles in AD, associated with learning abilities. They also give further hints for a functional differentiation between slow and fast spindles.

Several studies have suggested that anxiety may play a role in motion sickness susceptibility (MSS) variability. This study aimed to assess motion sickness susceptibility in healthy subjects and chronic vestibular patients and to investigate its relationship to gender, age and trait-anxiety. Healthy subjects (n=167) and chronic dizzy patients with various vestibulopathies (n=94), aged from 20 to 92 years old, were asked to complete Motion Sickness Susceptibility questionnaire (MSSQ) and trait-anxiety questionnaire (STAI-B). When patients were divided into those who had vestibular loss (n=51) vs. patients without vestibular loss (n=43), the MSSQ scores (mean ± SD) for patients with vestibular loss (18.8 ± 30.9) were lower than healthy subjects (36.4 ± 34.8), who were lower than vestibular patients without vestibular loss (59.0 ± 39.7). These significant differences could not be explained by gender, age, trait-anxiety, or interaction. Women had higher MSS than men, and MSS declined with age for healthy subjects and vestibular patients. The overall relationship between anxiety and MSS scores was weak and only reached significance in healthy subjects. These results support the conclusion that the vestibular system is heavily involved in MSS and that trait-anxiety may play a role in MSS but only in healthy subjects.

The aim of this study is to examine the effects of sleep deprivation during the first or second half of the night on episodic memory consolidation. Episodic memory is defined as memory for events located in time and space. It is also characterized by autonoetic consciousness, which gives a subject the conscious sensation of traveling back in time to relive the original event and forward into the future. Consolidation of episodic information was tested after 4-hour retention intervals, which followed learning and occurred during either the early or late half night, respectively dominated by slow wave sleep (SWS) or rapid eye movement (REM) sleep, or corresponding periods of wakefulness. Data collection occurred in the sleep laboratory. Forty-three young healthy subjects: 9 men and 34 women, age ranging from 18 to 26 years (mean 20.18 ± 1.94 years) were included in this study. Waking after a 4-hour retention interval filled with early or late sleep, or 4-hour sleep deprivation, during early or late period of night. The cognitive task, named the What-Where-When test, was specially designed to assess factual, spatial, and temporal components of episodic memory. This task was associated with the Remember/Know paradigm to assess autonoetic consciousness. We measured performance on immediate free recall, delayed free recall (after a 4-hour interval of wakefulness or sleep), and delayed recognition. We also calculated a forgetting rate for each feature (factual, spatial, and temporal) and, for the recognition task, scores of autonoetic consciousness (R responses). REM-sleep deprivation was associated with significantly lower recall of spatial information compared to SWS deprivation (P < .01) or late sleep (P < .05) conditions. REM-sleep deprivation was also associated with a higher forgetting rate of temporal information as compared to the early sleep condition (P < .01). Finally, REM-sleep deprivation led subjects to give significantly fewer R responses, indicative of true memories, as compared to SWS deprivation (P < .05). These results suggest that consolidation of truly episodic memories mainly involves REM sleep.