The Mesocortical System Encodes the Strength of Subsequent Force Generation

Abstract

Our minds impact motor outputs. Such mind-motor interactions are critical for understanding motor control mechanisms and optimizing motor performance. In particular, incentive motivation strongly enhances motor performance. Dopaminergic neurons located in the ventral midbrain (VM) are believed to be the center of incentive motivation. Direct projections from the VM to the primary motor cortex constitute a mesocortical pathway. However, the functional role of this pathway in humans remains unclear. Recently, we demonstrated the functional role of the mesocortical pathway in human motor control in the context of incentive motivation by using functional magnetic resonance imaging (fMRI). Incentive motivation remarkably improved not only reaction times but also the peak grip force in subsequent grip responses. Although the reaction time has been used as a proxy for incentive motivation mediated by dopaminergic midbrain activity, the premovement activity of the mesocortical pathway is involved in controlling the force strength rather than the initiation of subsequent force generation. In this commentary, we review our recent findings and discuss remaining questions regarding the functional role of the mesocortical pathway in mind-motor interactions.

Keywords: Ventral midbrain; force; motor cortex; reaction time; reward.

Figure 1.

Two distinct neural pathways control subsequent force generation under incentive motivation. Anticipating rewards increases premovement activity in both the ventral midbrain (VM) and primary motor cortex (M1). VM activity increases M1 premovement activity through direct mesocortical projections (red lines), enhancing the strength of the subsequently generated force. M1 premovement activity is increased through another neural pathway that might be mediated by the basal ganglia, leading to faster response times (blue lines).