SHAPE SELECTIVITY IN PRIMATE LATERAL INTRAPARIETAL CORTEX

The extrastriate visual cortex can be divided into functionally distin ct temporal and parietal regions, which have been implicated in featur e-related ('what') and spatial ('where') vision, respectively(1). Neur opsychological studies of patients with damage to either the temporal or the parietal regions provide support for this functional distinctio n(2-4). Given the prevailing modular theoretical framework and the fac t that prefrontal cortex receives inputs from both temporal and pariet al streams(5,6), recent studies have focused on the role of prefrontal cortex in understanding where and how information about object identi ty is integrated with (or remains segregated from) information about o bject location(7-10). Here we show that many neurons in primate poster ior parietal cortex (the 'where' pathway) show sensory shape selectivi ties to simple, two-dimensional geometric shapes while the animal perf orms a simple fixation task. In a delayed match-to-sample paradigm, ma ny neuronal units also show significant differences in delay-period ac tivity, and these differences depend on the shape of the sample. These results indicate that units in posterior parietal cortex contribute t o attending to and remembering shape features in a way that is indepen dent of eye movements, reaching, or object manipulation. These units s how shape selectivity equivalent to any shown in the ventral pathway.