Abstract
Neural mechanism underlying attention manifests itself through intertwined perceptual effects. A recent study using time-resolved behavioral measurements revealed that spatial attention mediates the processing of visual stimuli presented at precued location and uncued location in a rhythmic manner (Song et al., 2014). However, how the dynamics of spatial attention effects may interact with object/face representation is unknown. Here we combined this innovative time-resolved approach with fMRI to address this question. In each trial, an uninformative cue was presented in the left or right hemifield. Participants were asked to make speeded responses detecting whether a face or a house was presented at either the cued or uncued location. Critically, the cue-to-target stimulus onset asynchrony (SOA) varied trial-by-trial in a small step of 20ms, from 200ms to 1080ms. Bilateral fusiform face areas (FFA) and parahippocampal place areas (PPA) were localized with separate fMRI scans. On average across SOAs, in the left FFA, right hemifield targets led to significantly increased activity than left hemifield targets for both faces and houses. By contrast, averaged activity in the right FFA was invariant to which hemifield the target was shown, but significantly modulated by which hemifield the cue was presented, suggesting effects of spatial attention for face representation in the right FFA. No such hemispheric asymmetry was found for the PPA. Moreover, both the FFA and PPA results demonstrate theta-band oscillations in the valid cue condition, complementing to results we will report in other VSS2015 abstracts that suggest similar rhythmic effects of visual attention. Together, these results show 1) hemispheric asymmetry of how spatial attention and invariant face representation may interact; 2) reliable neural correlates of the theta-band behavioral oscillation underlying attention, shedding lights on how attention mechanisms dynamically regulate the neural processing of visual stimuli.
Meeting abstract presented at VSS 2015