Differential effects of non-REM and REM sleep on sensory gating in rats

Sensory gating in rats can be measured with a double click paradigm. The di minished response towards the second click is a physiological manifestation of reduced sensory input. This physiological process seems to be disturbed in human psychoses. It is thought that gating, as measured with this parad igm, is a preattentive, involuntary phenomenon which is not modulated by at tention. If this is indeed the case, than it is hypothesized that gating sh ould not be modulated by non-REM sleep. In the present experiment pairs of clicks (500 ms interval) were presented during wakefulness, non-REM as well as REM sleep and cortical auditory evoked potentials (AEP's) were recorded in chronically implanted rats. Rather similar AEP's were found after the f irst and second stimulus. However, the amplitudes of the various components of the second AEP were smaller than those of the first AEP, suggesting a g ated response. This was the case during all three levels of vigilance. The amplitudes of both AEP's showed the more often reported changes in amplitud e during sleep and REM sleep. Clear differences were seen in gating: compar ed to wakefulness a decrease in gating was found during REM sleep while gat ing was unchanged during non-REM sleep. The latter outcome seems to confirm that gating in rats is indeed a preattentive process. Finally, results wer e discussed in terms of neuronal properties of thalamic relay cells and it is suggested that firing properties of thalamic relay cells are not involve d in this type of sensory gating.