Event-related potentials (ERPs) were recorded during sleep onset and various stages of sleep. A late component of the ERP, P300, is elicited when subjects detect a rare "target" stimulus. It is usually not elicited when subjects fail to detect the stimulus. The presence of P300 has therefore been used to index the extent to which the sleeper is aware of their external environment. During the transition to sleep, subjects were asked to detect a rare 2000 Hz target occurring among a train of 1000 Hz standards. A parietal maximum P300 was apparent in wakefulness, and remained large to detected targets in stage 1 sleep. It was however attenuated at frontal sites in stage 1. There were few detections in stage 2 and P300 was not evident. ERPs were then recorded within sleep. Very loud stimuli were employed since loud deviants will elicit an obligatory P300 response in waking-ignore conditions. In Experiment 2, 90 dB SPL tone pips were delivered on 5% of trials and 70 dB SPL tones on remaining trials. A large parieto-central positive wave was recorded in REM sleep. In non-REM sleep, a later and more occipital positivity was observed. It remained unclear whether the REM P300 was due to the rareness or the loudness of the deviant. In Experiment 3, various intensities (0, 60, 80, 100 dB SPL) were therefore delivered at equal probability (p = .25). A parietal maximum P300 was again recorded in REM following the 100 dB tone, but was not apparent following the lower intensities. A frontal P300 was not apparent following the loud stimulus. In Experiment 4, pitch- and intensity-deviants were investigated during sleep and wakefulness (attend and ignore conditions). In three separate groups, the rare stimulus was delivered on either 20%, 10% or 5% of trials. The pitch-deviant did not elicit P300 in any condition. In the waking-ignore condition, the intensity-deviant elicited a parietal maximum P300 that extended into the frontal region. A large REM-specific P300 was apparent at parietal sites following the intensity-deviant when stimuli were delivered on 5% of trials, but was not apparent at frontal sites. These studies illustrate that P300 can be recorded during sleep onset and during REM sleep. Only stimuli which are sufficiently intrusive and rare will elicit the parietal P300 in REM. While subjects may be able to detect stimulus deviance in stage 1 and REM, the frontal contribution to consciousness may be absent.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/8709 |
| Date | January 1999 |
| Creators | Côté, Kimberly Ann. |
| Contributors | Campbell, Kenneth, |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 217 p. |
Page generated in 0.002 seconds