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The processes underlying dynamic changes in human behavior during real situations contain much irrelevant information and represent a key issue facing neuroscientists. Although the roles played by the frontal cortex in this switching behavior have been well documented, little is known regarding how neural pathways governing sensorimotor associations accomplish such a switch. We addressed this question by recording activities of middle temporal (MT) neurons in monkeys switching between direction versus depth discrimination tasks. Although the monkeys successfully switched between the tasks, neural sensitivity did not change as a function of task. More importantly, neurons that signaled the same motor output showed trial-to-trial covariation between neuronal responses and perceptual judgments during both tasks, whereas neurons that signaled the opposite motor output showed no covariation in either task. These results suggest that task switching is accomplished via communication from distinct populations of neurons when sensorimotor associations switch within a short time period.

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.

A new study has shown that neurons in the visual cortex are specialized to encode the larger range of horizontal - relative to vertical - disparities that occurs in central vision. These results challenge the established 'energy' model of disparity processing.