Neuronal modulation of the superior colliculus associated with visual spatial attention represents perceptual sensitivity, independent of perceptual decision and motor biases

Neurons in the superior colliculus (SC), like those in the cerebral cortex, are strongly modulated in response to shifts in attention, but make a contribution that is distinct from attention-related modulations in visual cortex. It has been a point of contention whether attention-related enhancement of neuronal activity in SC is associated with selective increase in behavioral sensitivity (d) in neurons response fields or with animals decision bias, which is closely linked with motor planning. By independently controlling monkeys perceptual decision and motor criterion, we show that SC activity is strongly correlated with perceptual sensitivity at the neurons response field. Responses of the same SC neurons were unchanged in the face of correspondingly large changes in the perceptual decision criterion. Furthermore, the SC activity did not convey information about perceptual detection on individual trials. These results suggest that the SC contributes to the component of attentional states related to heightened perceptual sensitivity.