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Caitlin Mullin, Jennifer Steeves; Transcranial magnetic stimulation to lateral occipital cortex disrupts object ensemble processing. Journal of Vision 2011;11(11):890. doi: https://doi.org/10.1167/11.11.890.
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© ARVO (1962-2015); The Authors (2016-present)
Several neuroimaging studies have reported that object processing selectively activates the lateral occipital area of the brain (LO). Processing in this area is most often studied by presenting a single object to the central visual field. However, the world outside of the laboratory is comprised of multiple objects. Frequently these objects are part of a larger collection or ensemble of objects. For instance, a flower bed or leaves on a tree contain homogeneous repeating and overlapping objects of different sizes and orientations. Recent neuroimaging evidence suggests that such ‘object ensembles’ show activation in area LO, much like single object displays. Additionally, object ensemble activation was observed in the scene selective parahippocampal place area. We asked whether transcranial magnetic stimulation (TMS) to LO would disrupt object ensemble processing, as has been shown with single object displays, which would suggest that ensembles recruit similar cortical areas to isolated objects. If no disruption is observed, it may suggest that object ensembles are processed more like scenes, and rely more on cortical areas associated with scene processing. Participants categorized grayscale photographs of objects ensembles as ‘natural’ or ‘man-made’ while simultaneously receiving a double pulse of TMS at 10 Hz to functionally defined area LO and to the vertex as a control. Preliminary results demonstrate a significant disruption to categorization during the TMS to LO condition compared to the baseline and TMS to vertex conditions. This disruption may reflect an inability to form a statistical summation of the objects within the ensemble required for accurate categorization. Moreover, this finding suggests that area LO quickly processes shape information from more complex stimuli than single objects.
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