The effect of unilateral somatosensory stimulation on hemispheric asymmetries during slow wave sleep

Abstract

Study Objectives: To examine the effect of unilateral somatosensory stimulation on the laterally of delta band activity during slow wave sleep (SWS). Design: Participants napped for two hours on two separate days. Two types of vibratory stimuli were randomly presented to one hand: a short and more intense vibration (rare stimulus) and a long and less intense vibration (frequent stimulus). The vibratory stimuli were presented to participants once in SWS in alternating periods of stimulation and no stimulation. Electroencephalographic (EEG) recordings were obtained from homologous electrode sites and analyzed for asymmetry. Setting: State University of New York at Stony Brook. Participants: Eight right-handed college students (ages 18 to 24). Measurements & Results: Delta band activity (>0-3.906 Hz) at homologous electrode sites was obtained and an asymmetry index (AI) was derived. The A1 varied as a function of Stimulus Type (rare, frequent, no stimulus). Less asymmetry was observed after rare stimuli than after frequent or no stimuli. There was no difference in Al between right and left hand stimulation. Absolute delta power was greater to rare stimuli than to frequent or no stimuli. Amplitude of ERP (event-related potential) components during wakefulness and sleep were also examined. Conclusions: The results of this study do not support the idea that vibra tory stimulation of a given hand will disrupt sleep in the contralateral hemisphere. However, the results do support the idea that the human brain is capable of monitoring the environment without compromising slow wave sleep.