Sensory gating-out and gating-in in normal and schizophrenic participants

In contrast to sensory gating, the brain's ability to re-respond to relevant stimuli and the potential differences between healthy and schizophrenic participants have not been studied in great detail. Here, we explore what auditory paradigms are useful to measure this re-responding ability. Evoked potentials (EPs) were obtained from the Cz channel using 3 paired stimulus paradigms (pairs with equal stimuli {PE}, the second stimulus being lower {PL} or higher {PH} in frequency) and 2 short-train paradigms in which 5 identical stimuli were followed by a lower frequency stimulus (train lower {TL}) or higher frequency stimulus (train higher {TH}). Data were collected from 17 healthy control participants (NC) and 17 age and gender-matched patients with schizophrenia (SZ). Up to 4 data sets obtained on 4 different days were available for each participant. Ensemble averages were computed for each session, from which the P50, N100, and P200 latencies and amplitudes were obtained. No significant differences in amplitude or latency of the various EP components were found between the responses to the second stimulus obtained with the 5 paradigms. Neither did the responses to the fifth and sixth stimuli differ for the TL and TH paradigm, with the exception of the N100 latency of the fifth stimulus, which was longer for TH than TL for NC. Healthy participants had larger amplitudes and shorter latencies than the patients with schizophrenia for the responses to the first stimuli, with the latency differences continuing for the fifth and sixth response. Also, the amplitude and latency of the first response was larger than for the second response in both populations. In conclusion, none of the paradigms studied here, with the employed parameters, are useful to measure the re-responding ability of the brain. Also, the shorter latencies for the repeated stimulus suggest that the neural mechanism underlying attenuation of repeated stimuli is of a facilitating nature.