Shape selectivity in primate lateral intraparietal cortex.

The extrastriate visual cortex can be divided into functionally distinct temporal and parietal regions, which have been implicated in feature-related ('what') and spatial ('where') vision, respectively. Neuropsychological studies of patients with damage to either the temporal or the parietal regions provide support for this functional distinction. Given the prevailing modular theoretical framework and the fact that prefrontal cortex receives inputs from both temporal and parietal streams, recent studies have focused on the role of prefrontal cortex in understanding where and how information about object identity is integrated with (or remains segregated from) information about object location. Here we show that many neurons in primate posterior parietal cortex (the 'where' pathway) show sensory shape selectivities to simple, two-dimensional geometric shapes while the animal performs a simple fixation task. In a delayed match-to-sample paradigm, many neuronal units also show significant differences in delay-period activity, and these differences depend on the shape of the sample. These results indicate that units in posterior parietal cortex contribute to attending to and remembering shape features in a way that is independent of eye movements, reaching, or object manipulation. These units show shape selectivity equivalent to any shown in the ventral pathway.