Adult Auditory Evoked Vertex Potentials In Sleep

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Abstract
Slow vertex potentials, evoked by filtered clicks (1200 Hz), were recorded (Cz–M1) from 11 adults while awake, in light sleep or in deep sleep. Sleep was induced by small doses of secobarbital, about 2.5 mg/kg. The familiar waking response pattern, N90–P170, was judged present or absent according to 5 voltage criteria, and the percentage of correct identifications (hit rate) and the percentage of false-positive judgments were related also to the sensation levels of the stimuli. If a 17-percent false-positive rate for a single trial is considered clinically acceptable, the best voltage criterion is about 3.3 μV. This gives a hit rate of about 80% for 20 dB SL clicks. The depth of sleep was estimated by the amount of dealta activity in the EEG, recorded with a 2 to 4-Hz pass-band, a full-wave rectifier and an integrator. Sleep response patterns, later and higher in voltage than the waking response, were clear in deep sleep (stages 3 or 4). The most characteristic and stable component was P200–N330, as described by Ornitz et al. [1967a and b]. For this the best voltage criterion was about 5 μV, which, for 9 of the 11 subjects, gave a hit rate of about 60% for 20 dB SL clicks. In light sleep (stages 1 or 2) the P200–N330 response was often present but it could not be so reliably identified because an increased percentage of false-positive ‘responses’ required the use of a very strict criterion, about 8 μV.

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