The role of phasic and tonic rapid eye movement sleep in implicit memory consolidation

Sleep is essential for memory consolidation, yet its role in implicit visuomotor memory remains poorly understood. Rapid eye movement (REM) sleep, particularly its Phasic and Tonic sub-states, may contribute to this process. This study revisits data from Viczko et al. (2018) to examine Phasic and Tonic REM characteristics and electroencephalography activity in implicit visuomotor memory consolidation using the Serial Reaction Time Task.

Participants trained on an implicit visuomotor sequence and were tested post-training, after a sleep/wake interval, and 1 week later. Polysomnography was used to analyze sleep architecture, focusing on REM sub-states. Electroencephalography data during REM were assessed for theta power (~4-8 Hz) using event-related spectral perturbation. Eye movements were categorized into Phasic or Tonic REM, with task-specific regional activity examined over frontal (Fz) and motor areas (C4).

Increases in total REM sleep and Tonic REM sleep duration were observed during the experimental compared to the control night. Changes in Tonic REM sleep correlated with motor representation speed post-sleep. Event-related spectral perturbation analysis revealed enhanced theta power time-locked to Phasic and Tonic REM eye movements, with regionally specific task-related increases over Fz and C4 (but not contralaterally).

Findings suggest Tonic REM stabilizes visuomotor memory, with theta oscillations serving as electrophysiological markers of consolidation. Task-specific theta increases highlight regional specificity of memory processing during sleep. This study underscores the roles of REM sub-states in implicit visuomotor memory consolidation and the need to further explore sleep sub-states.