Comparison of decision-related signals in sensory and motor preparatory responses of neurons in Area LIP

Neurons in the lateral intraparietal area (LIP) of Macaques exhibit both sensory and oculomotor preparatory responses. During perceptual decision making, the preparatory responses have been shown to track the state of the evolving evidence leading to the decision. The sensory responses are known to reflect categorical properties of visual stimuli, but it is not known if these responses also track evolving evidence. We compared sensory and oculomotor-preparatory responses in the same neurons during a direction discrimination task when either the discriminandum (random dot motion) or an eye movement choice-target was in the neurons response field. Both configurations elicited task related activity, but only the motor preparatory responses reflected evidence accumulation. The results are consistent with the proposal that evolving decision processes are supported by persistent neural activity in the service of actions or intentions, as opposed to high order representations of stimulus properties.\n\nSIGNIFICANCE STATEMENTPerceptual decision making is the process of choosing an appropriate motor action based on perceived sensory information. Association areas of the cortex play an important role in this sensory-motor transformation. The neurons in these areas show both sensory- and motor-related activity. We show here that, in the macaque parietal association area LIP, signatures of the process of evidence accumulation that underlies the decisions are predominantly reflected in the motor-related activity. This finding supports the proposal that perceptual decision making is implemented in the brain as a process of choosing between available motor actions rather than as a process of representing the properties of the sensory stimulus.