Taking Attention Out of Context: Frontopolar Transcranial Magnetic Stimulation Abolishes the Formation of New Context Memories in Visual Search.

ABSTRACT

This study investigates the causal contribution of the left frontopolar cortex (FPC) to the processing of violated expectations from learned target-distractor spatial contingencies during visual search. The experiment consisted of two phases learning and test. Participants searched for targets presented either among repeated or nonrepeated target-distractor configurations. Prior research showed that repeated encounters of identically arranged displays lead to memory about these arrays, which then can come to guide search (contextual cueing effect). The crucial manipulation was a change of the target location, in a nevertheless constant distractor layout, at the transition from learning to test. In addition to this change, we applied repetitive transcranial magnetic stimulation (rTMS) over the left lateral FPC, over a posterior control site, or no rTMS at all (baseline; between-group manipulation) to see how FPC rTMS influences the ability of observers to adapt context-based memories acquired in the training phase. The learning phase showed expedited search in repeated relative to nonrepeated displays, with this context-based facilitation being comparable across all experimental groups. For the test phase, the recovery of cueing was critically dependent on the stimulation site Although there was evidence of context adaptation toward the end of the experiment in the occipital and no-rTMS conditions, observers with FPC rTMS showed no evidence of relearning at all after target location changes. This finding shows that FPC plays an important role in the regulation of prediction errors in statistical context learning, thus contributing to an update of the spatial target-distractor contingencies after target position changes in learned spatial arrays.