Using fMR-adaptation to track complex object representations in perirhinal cortex.

Brain regions in medial temporal lobe have seen a shift in emphasis in their role in long-term declarative memory to an appreciation of their role in cognitive domains beyond declarative memory, such as implicit memory, working memory, and perception. Recent theoretical accounts emphasize the function of perirhinal cortex in terms of its role in the ventral visual stream. Here, we used functional magnetic resonance adaptation (fMRa) to show that brain structures in the visual processing stream can bind item features prior to the involvement of hippocampal binding mechanisms. Evidence for perceptual binding was assessed by comparing BOLD (blood-oxygen-level-dependent) responses between fused objects and variants of the same object as different, non-fused forms (e.g., physically separate objects). Adaptation of the neural response to fused, but not non-fused, objects was in left fusiform cortex and left perirhinal cortex, indicating the involvement of these regions in the perceptual binding of item representations.