Unconscious goal pursuit strengthens voluntary force during sustained maximal effort via enhanced motor system state

Abstract

Abstract Shouting during sustained maximal voluntary contraction (MVC) has been shown to potentiate maximal voluntary force through the enhancement of motor cortical excitability. However, it is not clear whether excitatory input from areas other than the motor-related cortical area to the primary motor cortex (M1) induces muscular force-enhancing effects on sustained maximal force exertion. We investigated the effects of subliminal goal-priming with motivational reward on motor system state by examining motor evoked potentials to transcranial magnetic stimulation during sustained MVC, and assessing handgrip force. The results revealed that barely visible priming of an action concept, when combined with a reward in the form of a consciously visible positive stimulus, increased maximal voluntary force and reduced the silent period (i.e., reduced motor cortical inhibition). This is the first objective evidence linking the muscular force of subliminal reward-goal priming during MVC to the enhancement of motor system activity through the additional drive of subliminal reward-goal priming operating on the motor system, possibly via the potentiation of reward-linked dopaminergic system activity.