The effects of sleep deprivation on the N350 during the wake/sleep transition
This research addressed the impact of one night of sleep deprivation on the amplitude of a sleep-onset event-related potential (ERP), the N350, believed to reflect a breakdown in sleep-related inhibitory processes. There are no published studies examining differences between sleep ERPs before and after sleep deprivation. It was hypothesized that N350 amplitude would be larger post sleep deprivation compared to baseline. Ten subjects took two 20 m naps separated by a 20 m break at their normal bedtime. Tones were presented at three intensity levels (60, 75, and 90 dB) with a 5 second interstimulus interval and response requirement to each stimulus. Subjects were kept awake until their normal bedtime the following day, at which time they repeated the two-nap tone presentation procedure. Mean amplitude of averaged N350s obtained across tone intensity and wake/sleep state were compared between pre and post sleep deprived conditions using repeated measures statistical procedures. As expected, N350 emerged as subjects fell asleep. This effect was greater for more intense tones and largest at the CZ electrode. N350 was larger at times following deprivation compared to baseline. The expected interaction was seen only during Stage 2K sleep, which is suspect because of the limited number of trials used for this analysis. Increasing sleep pressure, and therefore the presumed amount of inhibitory activity, increased the amplitude of N350. These data fit into the current theory that N350 is a breakdown in sleep related inhibition, but do not exclude alternate interpretations.