Contribution of area MT to stereoscopic depth perception: choice-related response modulations reflect task strategy.

Due to the diversity of tuning properties in sensory cortex, only a fraction of neurons are engaged in a particular task. Characterizing the tuning properties of neurons that are functionally linked to behavior is essential for understanding how activity is "read out" from sensory maps to guide decisions. We recorded from middle temporal (MT) neurons while monkeys performed a depth discrimination task, and we characterized the linkage between MT responses and behavioral choices. Trial-to-trial response fluctuations of MT neurons with odd-symmetric ("Near," "Far") disparity tuning were predictive of monkeys' choices, whereas responses of neurons with even-symmetric tuning were not. This result cannot be explained by neuronal sensitivity or any other response property of MT neurons that we examined but is simply explained by the task strategy that monkeys learned during training. We suggest that this approach provides a physiological means to explore how task strategies are implemented in the brain.