Generalized associative representations in parietal cortex

Making associations between sensory stimuli is a critical aspect of behavior. We previously found that neurons in the lateral intraparietal area (LIP) of Macaca mulatta reflect learned associations between directions of moving visual stimuli. Individual LIP neurons might encode associations only for specific stimuli, such as motion directions; alternatively, they may encode more general associations whenever animals must decide between discrete alternatives. To test this, we asked whether LIP neurons encode learned associations between pairs of arbitrarily chosen static shapes and, in a separate task, whether the same neurons also encode associations between motion directions. Our experimental design dissociated the visual associations from the movements used to report those associations. We found robust encoding of the learned pair associations between shapes, and shape-pair-selective neurons tended to be selective for direction associations. These findings suggest that representing generic categorical outcomes may be a fundamental role of parietal neurons.