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Electrophysiological cues of the salience-based progression of attention

On The March 29, 2016

Raphaël Mizzi

Abstract :

When we open our eyes, the amount of visual information is such that we cannot process it all at once. The job of attention is to select and order visual items for this processing. With very short presentations, 100ms for instance, we know that the progression of automatic attention is based on visual salience. The focus of attention explores first the most salient location, the item the most different from its visual neighboring, and then the immediately less salient location, and so forth. What are the visual pathways that subtend such processes? Arguments have been given regarding the involvement of pathways that circumvent the geniculate nucleus that connects to striate areas. The extrageniculate pathways, which connect to parietal structures via the superior colliculus and the pulvinar, are widely thought to underlie such attentional processes. It has been proposed that extrageniculate pathways convey the information faster than the geniculate ones. We used EEG methods to test this asynchrony hypothesis. Volunteers were asked to make a judgment regarding a target among two distractors, items were presented for 100ms and were either of different sizes (inducing a salience-based progression) or all of same size (control condition). We expected results to show 1) a hierarchical pattern based on target’s size in behavioral variables in the salience condition, confirming the salience-based progression of attention, and 2) that ERP would also show such pattern. Finally, 3), an early parietal activation in the salience condition was expected according to the asynchrony hypothesis, attesting of the fast extrageniculate modulation. Preliminary results will be presented.