Both visual and haptic perception of object shape engage processing in the lateral occipital complex (LOC) and intraparietal sulcus (IPS). We found that the IPS regions (but not the LOC) are also active during visual and haptic perception of object location. The common processing in IPS regions during perception of both shape and location information suggests that activity in these regions during shape perception may reflect attention to the relative locations of parts of objects, whereas LOC activity may reflect global shape processing.

What is the role of visual imagery (VI) in mediating LOC activity during haptic processing of shape (HS)? We found that activations during HS of familiar objects overlapped extensively with those during VI, with the magnitudes of VI- and HS-evoked activation being strongly correlated across subjects. These findings were not true for unfamiliar objects. Analysis of effective connectivity showed that the VI and familiar HS tasks activated similar networks involving top-down pathways into the lateral occipital complex (LOC), whereas the unfamiliar HS task activated a substantially different network characterized by bottom-up inputs into the LOC. Thus, the role of visual imagery in haptic shape perception is prominent for familiar, but not unfamiliar, objects.