Modification of EEG asymmetry induced by auditory biofeedback loop during REM sleep in man

Auditory stimulation during REM sleep modulates REM electrophysiology and cognitive performance

REM sleep is critical for memory, emotion, and cognition. Manipulating brain activity during REM could improve our understanding of its function and benefits. Earlier studies have suggested that auditory stimulation in REM might modulate REM time and reduce rapid eye movement density. Building on this, we studied the cognitive effects and electroencephalographic responses related to such stimulation. We used acoustic stimulation locked to eye movements during REM and compared two overnight conditions (stimulation and no-stimulation). We evaluated the impact of this stimulation on REM sleep duration and electrophysiology, as well as two REM-sensitive memory tasks: visual discrimination and mirror tracing. Our results show that this auditory stimulation in REM decreases the rapid eye movements that characterize REM sleep and improves performance on the visual task but is detrimental to the mirror tracing task. We also observed increased beta-band activity and decreased theta-band activity following stimulation. Interestingly, these spectral changes were associated with changes in behavioural performance. These results show that acoustic stimulation can modulate REM sleep and suggest that different memory processes underpin its divergent impacts on cognitive performance.

Cerebral dominance, sleep and dream phenomena

Evidence from human and animal studies is discussed in relation to the role played by the cerebral hemispheres in the genesis of sleep and particularly dream phenomena. The inconclusiveness of such research is commented upon and suggestions for further research are outlined.

Sleep, brain activation and cognition

Some data have shown the presence of time-of-day effects in learning processes. We explore here whether the same phenomenon occurs during the night and how it relates to REM sleep. In an initial approach to the question, this paper points out the relationships between: 1) REM sleep and brain activation, and 2) REM sleep and information processing. The data are discussed in terms of a REM sleep implication on information processing and we examine the possibility of modifying this processing by acting on REM sleep.

Enhancement of memory by auditory stimulation during postlearning REM sleep in humans

REM sleep involvement in memory processes was demonstrated in animals and humans: 1) REM sleep deprivation impairs the memory fixation, 2) learning sessions are followed by modifications of REM sleep characteristics. Moreover, sleep patterns can be modified by applying auditory stimulations during REM sleep. We show that REM actual auditory stimulations significantly improve the retention of a Morse code learning task. These results are discussed in terms of brain activation.