Altered Task Demands Lead to a Division of Labor for Sensory and Cognitive Processing in MT

Neurons in the primate Middle Temporal (MT) area signal information about visual motion and work together with the lateral prefrontal cortex (LPFC) to support memory-guided comparisons of visual motion direction. These areas are reciprocally connected, and both contain neurons that signal visual motion direction in the strength of their responses. Previously, LPFC was shown to display marked changes in stimulus coding with altered task demands, including changes in selectivity for motion direction, trial-to-trial variability in responses, and comparison effects. Since MT and LPFC are directly interconnected, we sought to determine if MT neurons display similar dependence on task demands. We found that active participation in a motion direction comparison task affected both sensory and non-sensory activity in MT neurons. The activity of MT neurons signaling motion direction depended on task demands, forming three distinct groups: neurons for which direction information (1) increased, (2) decreased, or (3) was largely unaffected with increased task demands. These groups display marked differences in both sensory and cognitive components of their response, suggesting that subpopulations of MT neurons flexibly modify their signaling properties between sensory and cognitive processes to suit task demands.