Opposite-Direction Spatial Working Memory Biases in People With Schizophrenia and Healthy Control Participants

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BackgroundPeople with schizophrenia (PSZ) show impaired accuracy in spatial working memory (sWM), which is 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 previous 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 the longer-term synaptic plasticity that stores previous-trial information. MethodsWe 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 control participants. 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. ResultsPSZ showed opposite-direction serial dependence bias effects: Healthy control participants showed an attractive bias that increased over increasing delays whereas PSZ showed a repulsion bias that increased over delays. In PSZ, the magnitude of the repulsion bias negatively correlated with broad measures of cognitive ability and WM capacity. ConclusionsPSZ 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.