A MODEL OF MULTIPLICATIVE NEURAL RESPONSES IN PARIETAL CORTEX

Visual responses of neurons in parietal area 7a are modulated by a com bined eye and head position signal in a multiplicative manner. Neurons with multiplicative responses can act as powerful computational eleme nts in neural networks. In the case of parietal cortex, multiplicative gain modulation appears to play a crucial role in the transformation of object locations from retinal to body-centered coordinates. It has proven difficult to uncover single-neuron mechanisms that account for neuronal multiplication. Here we show that multiplicative responses ca n arise in a network model through population effects. Specifically, n eurons in a recurrently connected network with excitatory connections between similarly tuned neurons and inhibitory connections between dif ferently tuned neurons can perform a product operation on additive syn aptic inputs. The results suggest that parietal responses may be based on this architecture.