Poster E1, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
Polarity-dependent effects of biparietal tDCS on the interplay between top-down and bottom-up processes in visual attention
Magdalena Chechlacz1,2, Dario Cazzoli3, Joy J Geng4, Peter C Hansen2; 1University of Oxford, 2University of Birmingham, 3University of Bern, 4UC Davis
Visuospatial attention allows the allocation of limited neural processing resources to behaviourally relevant stimuli. The selection of task-relevant visual targets entails the processing of multiple competing stimuli and the suppression of distractors which may be either perceptually salient or perceptually similar to targets. The posterior parietal cortex (PPC) controls both the interaction between top-down (task-driven) and bottom-up (stimulus-driven) processes competing for attentional selection as well as the spatial distribution of attention. Transcranial direct-current stimulation (tDCS) can be used to modulate cognitive processes by affecting cortical excitability (i.e., anodal stimulation increases while cathodal stimulation decreases cortical excitability). We used tDCS applied bilaterally over the PPC to modulate the interaction between top-down and bottom-up processes in visual attention. We measured the accuracy of performance in a visual search task prior to and during three within-subjects stimulation sessions (sham, right cathodal/left anodal and left cathodal/right anodal) in which a lateralized (left or right visual field) target was presented alone or together with a contralateral similar or salient distractor. Consistent with prior studies, the perceptually salient distractor facilitated, while the similar distractor hampered, target detection. In addition to the main effect of stimulation, we found a significant interaction between stimulation, target location and distractor saliency. This finding was attributable to the opposite effects of right cathodal/left anodal versus left cathodal/right anodal stimulation on the detection of the target which was accompanied by a perceptually similar distractor. We conclude that biparietal-tDCS can alter the relationship between task-driven and stimulus-driven attentional selection in a polarity-dependent manner.
Topic Area: ATTENTION: Spatial