title: Lengthened temporal integration in schizophrenia.
abstract: Research in schizophrenia has tended to emphasize deficits in higher cognitive abilities, such as attention, memory, and executive function. Here we provide evidence for dysfunction at a more fundamental level of perceptual processing, temporal integration. On a measure of flicker fusion, patients with schizophrenia exhibited significantly lower thresholds than age and education matched healthy controls. We reasoned that this finding could result from a longer window of temporal integration or could reflect diminished repetition suppression: if every frame of the repeating stimulus were represented as novel, its perceived duration would be accordingly longer. To tease apart these non-exclusive hypotheses, we asked patients to report the number of stimuli perceived on the screen at once (numerosity) as they watched rapidly flashing stimuli that were either repeated or novel. Patients reported significantly higher numerosity than controls in all conditions, again indicating a longer window of temporal integration in schizophrenia. Further, patients showed the largest difference from controls in the repeated condition, suggesting a possible effect of weaker repetition suppression. Finally, we establish that our findings generalize to several different classes of stimuli (letters, pictures, faces, words, and pseudo-words), demonstrating a non-specific effect of a lengthened window of integration. We conclude that the visual system in schizophrenics integrates input over longer periods of time, and that repetition suppression may also be deficient. We suggest that these abnormalities in the processing of temporal information may underlie higher-level deficits in schizophrenia and account for the disturbed sense of continuity and fragmentation of events in time reported by patients.
authors.affiliation: Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Brent D
authors.initials: BD
authors.lastname: Parsons
authors.forename: Shilpa
authors.initials: S
authors.lastname: Gandhi
authors.forename: Elyse L
authors.initials: EL
authors.lastname: Aurbach
authors.forename: Nina
authors.initials: N
authors.lastname: Williams
authors.forename: Micah
authors.initials: M
authors.lastname: Williams
authors.forename: Adel
authors.initials: A
authors.lastname: Wassef
authors.forename: David M
authors.initials: DM
authors.lastname: Eagleman
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D005425:Flicker Fusion; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010468:Perceptual Disorders / Q000175:diagnosis / Q000209:etiology*; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D012559:Schizophrenia / Q000150:complications*; D014825:Vocabulary