Choice-induced inter-trial inhibition is modulated by idiosyncratic choice-consistency.

Humans constantly decide among multiple action plans. Carrying out one action usually implies that other plans are suppressed. Here we make use of inter-trial effects to determine whether suppression of non-chosen action plans is due to proactively preparing for upcoming decisions or due to retroactive influences from previous decisions. Participants received rewards for timely and accurate saccades to targets appearing left or right from fixation. Each block interleaved trials with one (single-trial) or two targets (choice-trial). Whereas single-trial rewards were always identical, rewards for the two targets in choice-trials could either be identical (unbiased) or differ (biased) within one block. We analyzed single-trial latencies as a function of idiosyncratic choice-consistency or reward-bias, the previous trial type and whether the same or the other target was selected in the preceding trial. After choice-trials, single-trial responses to the previously non-chosen target were delayed. For biased choices, inter-trial effects were strongest when choices were followed by a single-trial to the non-chosen target. In the unbiased condition, inter-trial effects increased with increasing individual consistency of choice behavior. These findings suggest that the suppression of alternative action plans is not coupled to target selection and motor execution but instead depends on top-down signals like the overall preference of one target over another.