Representing connected and disconnected shapes in human inferior intraparietal sulcus

Although human lesion data have indicated the importance of the parietal cortex in object-based representations, our understanding of parietal object grouping and selection mechanisms in normal observers remains largely incomplete. This study manipulated the grouping between shapes and found that fMRI response from the inferior intraparietal sulcus (IPS) was higher for the disconnected (ungrouped) than for the connected (grouped) shapes in a task in which observers simply watched the displays and performed a simple image motion jitter detection task. These results replicated similar findings from a previous study employing a different paradigm and showed that the inferior IPS plays an important role in tracking the grouping between visual elements during visual perception. Assuming that a lower response corresponds to a greater ease of representation, these results may explain why after parietal brain lesions grouped visual elements are easier to perceive than ungrouped ones.