Opposite-direction spatial working memory biases in people with schizophrenia and healthy controls.

Background: People with schizophrenia (PSZ) show Impaired accuracy in spatial working memory (SWM), thought to reflect abnormalities in the sustained firing of feature selective neurons that are critical for successful encoding and maintenance processes. Recent research has documented a new source of variance in the accuracy of SWM: In healthy adults, SWM representations are unconsciously biased by prior trials such that current-trial responses are attracted to previous-trial responses (serial dependence). This opens a new window to examine how schizophrenia impacts both the sustained neural firing representing the current-trial target and longer-term synaptic plasticity that stores previous-trial information.

Methods: We examined response accuracy in a single-item SWM test with delay intervals of 0, 2, 4, or 8 seconds in 41 PSZ and 32 demographically similar healthy controls (HCS). Our main dependent variable was the bias index, which quantifies the extent to which the current-trial responses were biased toward or away from the previous-trial target.

Results: PSZ showed opposite-direction serial dependence bias effects: HCS showed an attractive bias which increased over increasing delays whereas PSZ showed a repulsion bias that increased over delays. In PSZ, the magnitude of the repulsion bias correlated negatively with broad measures of cognitive ability and WM capacity.

Conclusions: PSZ show opposite-direction effects of previous trials on WM. Such qualitatively distinct differences in performance are extremely rare in psychopathology and may index a fundamental alteration in neural processing that could serve as a valuable biomarker for pathophysiology and treatment development research.