The Right Angular Gyrus Combines Perceptual and Response-related Expectancies in Visual Search: TMS-EEG Evidence

Visual search performance is sensitive to changes in the environment. Attention is sensitive to trial history, in terms of both perception and response. Although the bases of these sensorimotor interactions remain unclear, both behaviorally and neurally, converging evidence from a variety of methods indicates that the right angular gyrus (rANG) may be important.

The present study tests whether the rANG plays a causal role in generating these inter-trial effects.

Participants performed a compound task for feature singleton targets. We applied rTMS over the rANG (or a control site, or no TMS) during the inter-trial interval and measured effects both on behavior and on neural activity using psychophysics and event-related potential (ERP) recording.

rANG TMS during the inter-trial interval improved performance to the upcoming stimuli only when the target-defining dimension and the response-defining feature both repeated across successive trials. rANG TMS also increased the amplitude of the visual N1 component evoked by the upcoming stimuli. These effects did not occur after control TMS.

rANG plays a causal role in the formation of combined expectancies binding together stimulus- and response-characteristics of the previous trial to optimize visual search performance. This supports a visuomotor theory of parietal cortex and the dimension weighting account of attention. We suggest current models of inter-trial effects in visual search need to be expanded to include an interactive component representing both perceptual and motoric inter-trial expectancies, affecting the early analysis of stimulus features in the upcoming trial.