Global-local visual processing in schizophrenia: evidence for an early visual processing deficit.

BACKGROUND

Abnormalities in early-stage visual processing might contribute to observed higher neurocognitive deficits in schizophrenia, but to date no clear link has been established. Schizophrenia has been associated with deficits in the magnocellular visual pathway, suggesting a relative bias for processing elemental (local) as opposed to configural (global) aspects of a hierarchical stimulus; however, global-local paradigm studies in schizophrenia have yielded mixed results.

METHODS

In the current study, global-local and event-related potential (ERP) procedures were concomitantly used to assess temporal and spatial characteristics of hierarchical visual stimulus processing abnormalities.

RESULTS

Patients (n = 24) had slower and less accurate responses to global stimuli than a healthy comparison group (n = 29). They exhibited a marked decrement in N150 ERP amplitude, which correlated with speed of response to global stimuli. They also failed to show an augmented P300 response to local stimuli.

CONCLUSIONS

Behavioral and physiological data are consistent and support a global visual processing deficit in schizophrenia. This is manifest at a relatively early stage of visual processing and might relate to physiological disturbances in areas V3/V3a of the extrastriate cortex.