Humans have an amazing ability to quickly and efficiently recognize and interact with visual objects in their environment. The underlying neural processes supporting this ability have been mainly explored in the ventral visual stream. However, the dorsal stream has been proposed to play a critical role in guiding object-directed actions (Goodale & Milner, 1992). This hypothesis is supported by recent neurophysiology and neuroimaging studies that identified object-selective neural responses in the dorsal stream. For example, there is evidence for a striking similarity in the representation of basic object information in the two pathways (Konen & Kastner, 2008) with higher-order areas in lateral occipital/ventral temporal and posterior parietal cortex responding selectively to objects independent of changes in size and viewpoint. Another line of research has identified object-related activity in more anterior regions of the intraparietal sulcus (IPS), especially for images of tools (e.g., Chao & Martin, 2000). Here, we sought to more clearly delineate object information in the anterior portions of the IPS with respect to topographically defined regions of interest using an adaptation paradigm. Subjects viewed blocks of 2D or 3D shapes under adapted (1 object presented 16 times) or non-adapted (16 objects presented 1 time) conditions. Adaptation effects were observed in and around topographically organized area IPS5, which is located in the most anterior aspects of the IPS, for 3D, but not 2D objects and only in the left, but not the right hemisphere. Interestingly, this activity was located posterior to motor-related grasping activity (actual grasping vs. reaching; Culham et al., 2003), suggesting that it is not a motor representation, per se. Together with our previous studies, these results suggest that posterior regions of the IPS act as a perceptual hub for general object information, whereas more anterior regions selectively represent object properties that are critical for guiding action.
NSF, NIH/NIMH, NIH/NINDS, Princeton University, Luce Foundation.