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Daniel Baldauf, Robert Desimone; Neural mechanisms of object-based attention. Journal of Vision 2014;14(10):1119. doi: 10.1167/14.10.1119.
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Attention to a location in space is thought to be mediated by feedback to visual cortex from spatially-mapped control structures such as the frontal eye field, but how we attend to objects and features that cannot be separated by location is not understood. We addressed this question with a combination of MEG and fMRI. We presented two temporally and spatially overlapping streams of objects, faces versus houses, and used a frequency-tagging approach to separate responses to attended and unattended stimuli. Attention to faces versus houses enhanced the sensory signals in the fusiform face area (FFA) and parahippocampal place area (PPA), respectively, as well as in a particular portion of the prefrontal cortex, the inferior frontal junction (IFJ); however, the FFA and PPA frequency-tagged sensory signals were advanced in phase by 25ms compared to IFJ, i.e. the sensory transmission time. By contrast, the top-down information for attention to faces and houses was associated with gamma frequency synchronization between the IFJ and the FFA and PPA respectively, and the IFJ led these areas by an equivalent 25ms, in gamma phase, i.e. the feedback transmission time. With these delays, activity in one area would be optimally timed to impact processing in the connected area. DTI tractography confirmed that the IFJ was connected with both FFA and PPA. Thus, the IFJ seems to be a key source of signals for object-based attention, and it modulates the sensory processing of objects at least in part through phase-advanced gamma-frequency synchronization.
Meeting abstract presented at VSS 2014
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