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Joakim K. Vinberg, Kalanit Grill-Spector; Object and shape processing in the human lateral occipital complex. Journal of Vision 2005;5(8):86. doi: 10.1167/5.8.86.
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© ARVO (1962-2015); The Authors (2016-present)
The human lateral occipital complex (LOC) has been implicated in object perception (Grill-Spector 2003), shape perception (Kourtzi & Kanwisher, 2001) and also in segmenting salient regions (Stanley & Rubin, 2003). However, previous studies have used shaped stimuli and have not dissociated between these processes. Here we asked whether the LOC processes objects, shapes or salient surfaces?
To examine whether the LOC is involved in surface-segmentation we contrasted activation to segmentable and unsegmentable random dot stereograms. Segmentable stimuli contained two depth planes, and unsegmentable stimuli contained random disparities. To examine whether LOC is involved in shape processing we contrasted activation to trials that contained a shaped aperture in the front surface (aperture condition) to segmentable depth planes. Finally, to examine the role of the LOC in object processing we contrasted activation to trials containing an object above a surface to the aperture condition. Shape contours were identical for the object and aperture conditions. Nine subjects were scanned on a 3T scanner and were asked to respond if the fixation was on the front or back surface. To test the generality of our findings, the same subjects participated in a second experiment in which we presented analogous stimuli composed of moving dots.
In both experiments, the aperture and object conditions elicited a significantly higher response in LOC than two surfaces or random noise. Further, activation to two surfaces was not significantly higher than to random noise. These results suggest that the LOC is not involved in processing of salient surfaces, but rather in shape and object processing. In addition, we observed a hierarchical processing of shape along the ventral stream: posterior regions (LO) responded more strongly to objects and shaped apertures than to surfaces or noise, while anterior regions along the fusiform responded more strongly to objects than shaped apertures.
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