Center-surround processing in psychosis

Area of Science:

• Neuroscience
• Visual Perception
• Psychopathology

Background:

• People with psychotic psychopathology (PwPP) exhibit altered visual perception.
• Contrast surround suppression is a visual illusion where surrounding patterns reduce the perceived contrast of a central pattern.
• PwPP typically show weaker contrast suppression than controls, but underlying mechanisms remain unclear.

Purpose of the Study:

• To investigate perceptual and neural surround suppression in controls, relatives of PwPP, and PwPP.
• To explore neural mechanisms contributing to diminished surround suppression using fMRI and MR spectroscopy.
• To assess GABA concentration in occipital cortex and its relation to visual processing.

Main Methods:

• Assessed surround suppression in 38 controls, 44 relatives, and 64 PwPP.
• Quantified contrast discrimination thresholds and 7 tesla fMRI responses in LGN, V1, and LOC.
• Measured occipital GABA concentration using 7 T MR spectroscopy.

Main Results:

• LOC showed weaker surround suppression in PwPP and relatives compared to controls.
• No significant differences in V1 surround suppression strength were found across groups.
• No behavioral evidence of reduced surround suppression in PwPP; suppression metrics did not correlate with GABA or symptoms.
• V1 fMRI revealed group differences in decoding surround context, with lower accuracy in PwPP.

Conclusions:

• Subtle differences in visual center-surround processing exist in people with schizophrenia.
• Discrepancies with prior studies may stem from task design or attentional differences.
• Poorer decoding of center vs. surround in V1 suggests less reliable neural representations of spatial context in PwPP.