Structured interview for assessing perceptual anomalies (SIAPA)

Clinical descriptions of perceptual and attentional anomalies in schizophre nia emphasize phenomena such as flooding, or inundation, by sensory stimuli . A failure of sensory "gating" mechanisms in the brain is hypothesized to account for these symptoms, and this hypothesis has led to a marked interes t in their putative psychophysiological substrates. However, there are no s ystematic analyses of the phenomenology of these perceptual experiences, no r has the hypothesized connection between the clinical phenomena and their reported psychophysiological substrates been tested. In this investigation, a structured interview instrument was developed to measure perceptual anom alies as distinct from hallucinations and to determine their prevalence acr oss sensory modalities in schizophrenia in 67 schizophrenia subjects and 98 normal controls. The instrument includes Likert ratings of hypersensitivit y, inundation, and selective attention to external sensory stimuli. Good in terrater agreement, determined from interviews, was obtained. Schizophrenia subjects had significantly higher auditory, visual, and combined scores (i .e., across all modalities) than normal controls did, indicating significan tly more perceptual anomalies. For the schizophrenia group, the prevalence of auditory and visual anomalies was significantly greater than the other s ensory modalities. The data indicate that the putative phenomenological cor relates of sensory gating may be reliably measured and tested with the Stru ctured Interview for Assessing Perceptual Anomalies.