Subjects with schizotypal personality disorder may have trait-linked sensory gating deficits similar to those in patients with schizophrenia and their relatives. Because these subjects may manifest sensory gating deficits without overt psychotic symptoms, it is likely that these deficits represent a core cognitive dysfunction of the schizophrenia spectrum.

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Background: Individuals with schizophrenia spectrum diagnoses have deficient visual information processing as assessed by a variety of paradigms including visual backward masking, motion perception and visual contrast sensitivity (VCS). In the present study, the VCS paradigm was used to investigate potential differences in magnocellular (M) vs. parvocellular (P) channel function that might account for the observed information processing deficits of schizophrenia spectrum patients. Specifically, VCS for near threshold luminance (black/white) stimuli is known to be governed primarily by the M channel, while VCS for near threshold chromatic (red/green) stimuli is governed by the P channel.Methods: VCS for luminance and chromatic stimuli (counterphase-reversing sinusoidal gratings, 1.22 c/degree, 8.3 Hz) was assessed in 53 patients with schizophrenia (including 5 off antipsychotic medication), 22 individuals diagnosed with schizotypal personality disorder and 53 healthy comparison subjects.Results: Schizophrenia spectrum groups demonstrated reduced VCS in both conditions relative to normals, and there was no significant group by condition interaction effect. Post-hoc analyses suggest that it was the patients with schizophrenia on antipsychotic medication as well as SPD participants who accounted for the deficits in the luminance condition.Conclusions: These results demonstrate visual information processing deficits in schizophrenia spectrum populations but do not support the notion of selective abnormalities in the function of subcortical channels as suggested by previous studies. Further work is needed in a longitudinal design to further assess VCS as a vulnerability marker for psychosis as well as the effect of antipsychotic agents on performance in schizophrenia spectrum populations.

Right and left hemisphere contributions to perceptual organization functions were examined using a divided-attention version of the global-local task in a sample of 21 unmedicated participants diagnosed with schizotypal personality disorder (SPD) and 20 controls. The SPD participants showed an abnormal global processing advantage. When the visual angle of the hierarchical stimuli was increased from 3 degrees to 9 degrees, the controls showed an increasing local processing advantage, but the SPD participants continued to show an abnormal global processing advantage. These findings suggest a local processing deficit on divided-attention versions of the global-local task in schizophrenia spectrum disorders. Female SPD participants, who had less severe interpersonal deficit symptoms, showed a more abnormal global processing advantage. Hemispheric and processing resource mechanisms that might explain these findings are discussed.

Background Patients with schizophrenia consistently demonstrate information processing abnormalities assessed with visual masking (VM) tasks, and these deficits have been linked to clinical and functional severity. It has been suggested that VM impairments may be a vulnerability marker in individuals at risk for developing psychosis. Method Forward and backward VM performance was assessed in 72 first-episode (FE) psychosis patients, 98 subjects at risk (AR) for psychosis and 98 healthy controls (HC) using two identification tasks (with either a high- or low-energy mask) and a location task. VM was examined for stability in a subgroup (FE, n=15; AR, n=35; HC, n=21) and assessed relative to clinical and functional measures. Results In the identification tasks, backward VM deficits were observed in both FE and AR relative to HC whereas forward VM deficits were only present in FE patients compared to HC. In the location task, AR subjects demonstrated superior performance in forward VM relative to HC. VM performance was stable over time, and VM deficits were associated with baseline functional measures and predicted future negative symptom severity in AR subjects. Conclusions Visual information processing deficits, as indexed by backward VM, are present before and after the onset of frank psychosis, and probably represent a stable vulnerability marker that is associated with negative symptoms and functional decline. Additionally, the paradoxically better performance of AR subjects in select forward tasks suggests that early compensatory changes may characterize an emerging psychotic state.