Altered short-term neural plasticity related to schizotypal traits: Evidence from visual adaptation

Abnormalities in synaptic plasticity are argued to underlie the neural dysconnectivity observed in schizophrenia. One way to measure synaptic plasticity is through sensory adaptation, whereby sensory neurons exhibit reduced sensitivity after sustained stimulus exposure. Evidence for decreased adaptation in individuals with schizophrenia is currently inconclusive, possibly due to heterogeneity in clinical and medication status across samples. Here we circumvent these confounds by examining whether altered adaptation is represented sub-clinically in the general population. To test this we used three paradigms from visual perception research that provide a precise and non-invasive index of adaptation in the visual system. Two paradigms involve a class of illusory percepts termed visual aftereffects. The third relies on a visual phenomenon termed binocular rivalry, where incompatible stimuli are presented to the two eyes and observers alternate between perceiving exclusively one stimulus or a combination of the two (i.e. mixed perception). We analyzed the strength and dynamics of visual adaptation in these paradigms, in relation to schizotypy. Our results showed that increased schizotypal traits were related to reduced orientation, but not luminance, aftereffect strength (Exp. 1). Further, increased schizotypy was related to a greater proportion of mixed perception during binocular rivalry (Exp. 1 and 2). Given that visual adaption is well understood at cellular and computational levels, our data suggest that short-term plasticity in the visual system can provide important information about the disease mechanisms of schizophrenia.