Orientation-dependent contextual modulation of contrast in schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Visual Perception

Background:

• Schizophrenia is linked to impaired visual contrast perception, often attributed to altered neural activity in the primary visual cortex (V1).
• Previous research suggested weakened contextual modulation in V1 for individuals with schizophrenia.

Purpose of the Study:

• To investigate atypical contextual modulation mechanisms in the primary visual cortex (V1) in schizophrenia using high-field fMRI.
• To assess both V1-intrinsic and V1-extrinsic factors contributing to altered visual processing.

Main Methods:

• Examined BOLD responses in individuals with schizophrenia (n=34), bipolar disorder (n=25), relatives (n=33), and controls (n=23).
• Utilized a novel task presenting gratings with near- and far-surrounds at varying orientations (20° and 70°).

Main Results:

• Observed significant orientation-dependent contextual modulation of V1 BOLD activation in both schizophrenia and control groups.
• Found that the direction of modulation was opposite to predictions, with increased activation where suppression was expected.

Conclusions:

• Contrary to previous reports, orientation-dependent modulation of V1 activation was observed in individuals with schizophrenia.
• Spatial attention and figure-ground modulation mechanisms may significantly influence the observed orientation-dependent modulation in V1.