Parietal and Motor Cortical Dynamics Differentially Shape the Computation of Choice History Bias

Humans and other animals tend to systematically repeat (or alternate) their previous choices, even when judging sensory stimuli presented in a random sequence. Choice history biases may arise from action preparation in motor circuits, or from perceptual or decision processing in upstream areas. Here, we combined source-level magnetoencephalographic (MEG) analyses of cortical population dynamics with behavioral modeling of a visual decision process. We disentangled two neural history signals in human motor and posterior parietal cortex. Gamma-band activity in parietal cortex tracked previous choices throughout the trial and biased evidence accumulation toward choice repetition. Action-specific beta-band activity in motor cortex also carried over to the next trial and biased the accumulation starting point toward alternation. The parietal, but not motor, history signal predicted the next trial's choice as well as individual differences in choice repetition. Our results are consistent with a key role of parietal cortical signals in shaping choice sequences.