After effects of noise-induced sleep disturbances on inhibitory functions.

The study focuses on possible after effects of noise-induced sleep disturbances on inhibitory brain processes reflecting in performance changes and alternations of inhibition-related components of event-related potentials (ERPs). Following a quiet night and three nights, in which railway noise was presented with different levels, twelve women and ten men (19-28 years) performed a visual Go/Nogo task that contained stimuli either compatible or incompatible with a response. Noise-induced sleep disturbances are highly evident in worsening of subjective sleep quality but did not show up in significant changes of reaction time and error rate. A smaller N2 amplitude and longer latency to incompatible than to compatible stimuli as well as an unspecific attenuation of N2 amplitude under Noise were found. The amplitude of the fronto-central P3 was reduced under Noise compared to baseline only in Nogo trials. The amplitude of the parietal P3 in Go trials was smaller to incompatible than to compatible stimuli but was not affected by Noise. Disturbed sleep was associated with a decreased blink rate during task performance. The results suggest that physiological costs to maintain performance are increased after noisy nights. Decisional processes underlying overt responses (Go-P3) are less vulnerable to noise-disturbed sleep than those related to inhibition (Nogo-N2, NoGo-P3). The deficits may have been compensated by increased on-task concentration and thereby did not become apparent in the performance data. Inhibition-related ERPs may be more sensitive indicators of moderate sleep disturbances caused by noise than performance measures.