Mismatch negativity in detection of interval duration deviation in schizophrenia.

Temporal processing deficits have been noted in behavioral studies assessing patients with schizophrenia. The current study sought to explore the physiology of temporal perception while controlling the effects of motivation, attention and other cognitive processes that may contribute to behavioral measures of temporal processing. Mismatch negativity (MMN) waveforms were measured in response to variations in the temporal parameters of an ongoing train of pure tones. A standard inter-stimulus interval of 400 ms was interrupted, on average, every 20th tone by an inter-stimulus interval of 340 ms. Amplitude of MMN waveform elicited by the temporal deviance was significantly reduced in the schizophrenia group compared with controls (p = 0.016). Results suggest that behavioral difficulties on time processing tasks in schizophrenia may reflect a physiological deficit in temporal perception in this population rather than simply more general difficulties in attention or motivation.

Sensory gating impairment associated with schizophrenia persists into REM sleep.

Physiological measures of sensory gating are increasingly used to study biological factors associated with attentional dysfunction in psychiatric and neurologic patient populations. The present study was designed to assess sensory gating during rapid eye movement (REM) sleep in patients with schizophrenia, a population bearing a genetic load for gating impairment. Auditory event-related potentials (ERPs) were recorded in response to paired clicks during separate waking and overnight sleep recording sessions in controls and schizophrenia patients. Suppression of ERP component P50 was significantly impaired in the patient group during both waking and REM sleep, whereas the difference between groups for N100 gating was dependent on state. These results suggest that REM sleep is an appropriate state during which to assess P50 gating in order to disentangle the effects of state and trait on sensory gating impairment in other clinical populations.

Early postnatal development of sensory gating.

Sensory gating represents the nervous system's ability to inhibit responding to irrelevant environmental stimuli. In order to characterize the early development of acoustic sensory gating, suppression of auditory evoked potential component P1 (i.e. P50) in response to paired clicks was measured during REM sleep in healthy infants (1-4 months) that were without genetic risk for disrupted sensory gating function (i.e. having a relative with schizophrenia). As a group, the subjects exhibited significant response suppression. A correlation between increasing age and stronger response suppression was uncovered, even within this restricted age range. Parallel changes in sleep physiology could not be ruled out as the explanation for this change. Nevertheless, these results demonstrate that the neural circuits underlying sensory gating are functional very early in postnatal development.