Electrophysiological measures of attentional processes in man as related to the study of schizophrenia

Abstract

interferes with the ability to “filter out” irrelevant sensory information either because of a defect with the “filter” itself4 or because of a malfunction with the filter’s control system.516 Other authors argue that schizophrenia is associated with a partial collapse of response hierarchies, resulting in an increase in the probability of issuing inappropriate responses.7 Support for either position, as derived from behavioral measures, has been difficult to interpret. This difficulty stems in part from the problem of how to assess the selectivity of perception with behavioral tests. The traditional approach of testing the patient’s performance both with and without distracters present suffers from a serious weakness. By simply comparing performance on a given perceptual task in two different stimulus environments, one cannot ascertain whether the data reflect selective attention (i.e. a selective or di#erentiuZ allocation of processing capacity to the relevant stimuli in the environment) or general attentiveness (i.e. changes in the overall amount of processing capacity), or both. It is reasonable to suppose that an individual would become more generally attentive when placed in a more demanding task situation where distracters are present, as well as becoming more selective in his processing. A better methodological approach is to have a subject focus his attention on each of two (or more) sets of stimuli in turn in the same environment, and then to divide his attention across both sets concurrently. Ifperformance on each set is degraded in the divided attention condition relative to when attention was focused on the corresponding set, then one can infer that selective processing was operating during focused attention. This approach, however, *Supported by USPHS Grant MH 25594-01 to Steven A. Hillyard and NASA Grant NCR 05-009-198 to Robert Galambos. Grateful thanks are extended to Pennie Hink for her help with the preparation of the