Poster E6, Monday, March 26, 2:30-4:30 pm, Exhibit Hall C
The neural timecourse of the endogenous shifting of attention to objects
Charles Giattino1, Saikiran Gudla1, Marty Woldorff1; 1Duke University
Attention can be directed endogenously to spatial locations, as well as to features and objects in the environment. Attending to objects has been shown to modulate fMRI BOLD activity in object-selective cortical areas; e.g., attending to faces increases activity in the fusiform face area. However, fMRI cannot reveal the timecourse of such attentional modulations, nor the specific nature of the neuroelectric signals involved. We sought to elucidate the timecourse of object-based attention by recording EEG as subjects performed two different tasks. In a “localizer” task, subjects were centrally presented with a series of face and house images, one at a time, with the task to detect occasional blurred images in the series and respond as to their object category. We used the scalp topography of the face-selective (face-minus-house) N170 ERP effect in individual subjects in this task as a template for object-selective processing. In the main task, subjects were presented with both a face and house, one above and one below fixation. After 800-900 ms, subjects were cued to shift attention to either the face or house to detect a subsequent, transient blurring of the image. We found that shifting attention to faces (compared to houses) induced a highly similar pattern of voltages to the localizer-task N170, starting at ~400 ms post-cue and continuing until the end of the trial. We also found an N170-like pattern earlier in the trial, at ~200 ms post-cue, activity suggestive of a rapid, learned association that occurs before the endogenously controlled shift of attention.
Topic Area: ATTENTION: Nonspatial