Abstract
Contour integration is impaired in schizophrenia patients, even at the first episode, but little is known about visual integration abilities prior to illness onset. To examine this issue, we compared undergraduate students high and low in schizotypal personality traits, reflecting putative liability to psychosis, on two psychophysical tasks assessing local and global stages of the integration process. The Radial Frequency Jittered Orientation Tolerance (RFJOT) task measures tolerance to orientation noise at the local signal level, when judging global stimulus orientation, whilst the Radial Frequency Integration Task (RFIT) measures the ability to globally integrate the local signals that have been extracted during shape discrimination. Positive schizotypy was assessed with the Perceptual Aberration (PAb) scale from the Wisconsin Schizotypy Scales-Brief. On the RFJOT task, the High PAb group (n = 55) tolerated statistically significantly less noise (d = −0.494) and had a lower proportion of correct responses (d = −0.461) than the Low PAb group (n = 77). For the RFIT there was no statistically significant difference in integration abilities between the High and Low PAb groups. High and Low PAb groups also differed on other positive and disorganized (but not negative) schizotypy traits, hence poorer performance on the RFJOT may not be solely related to unusual perceptual experiences. These findings suggest that difficulties with local noise tolerance but not global integration occur in healthy young adults with high levels of schizotypal personality traits, and may be worth investigating as a marker of risk for schizophrenia.
Highlights
Visual perceptual disturbances are common in schizophrenia [1, 2] and in schizotypy [3, 4]—a cluster of personality traits reflecting a putative liability to schizophrenia-spectrum disorders in the general population [5, 6]
The High Perceptual Aberration (PAb) group displayed less tolerance to noise at the local signal level on the Radial Frequency Jittered Orientation Tolerance (RFJOT) task, indicating poorer integration of local orientation information than the Low PAb group
Contrary to expectation, we found that global integration efficiency, assessed on the Radial Frequency Integration Task (RFIT) task, was intact in high positive schizotypes
Summary
Visual perceptual disturbances are common in schizophrenia [1, 2] and in schizotypy [3, 4]—a cluster of personality traits reflecting a putative liability to schizophrenia-spectrum disorders in the general population [5, 6]. There has been a strong research interest in contour integration as an index of PO, using the Jittered Orientation Visual Integration [JOVI; [14]] task, which measures an individual’s ability to tolerate orientation noise at the local signal level when evaluating the shape of a global contour formed from these elements. In this task, the stimulus is a field of randomly oriented (but relatively evenly spaced) Gabor patches, containing the target shape (commonly an egg-shape). This task has received strong research interest, and consistently revealed poorer performance in schizophrenia patients [e.g., [14,15,16,17]], as early as the first psychotic episode [18], much less is known about these particular integration abilities in healthy individuals with high levels of schizotypy, who are at increased risk for schizophrenia
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