Modulation of corticospinal excitability by reward depends on task framing

Abstract

Findings from previous transcranial magnetic stimulation (TMS) experiments suggest that the primary motor cortex (M1) is sensitive to reward conditions in the environment. However, the nature of this influence on M1 activity is poorly understood. The dopamine neuron response to conditioned stimuli encodes reward probability and outcome uncertainty, or the extent to which the outcome of a situation is known. Reward uncertainty and probability are related: uncertainty is maximal when probability is 0.5 and minimal when probability is 0 or 1 (i.e., certain outcome). Previous TMS-reward studies did not examine these factors independently. Here, we used single-pulse TMS to measure corticospinal excitability in 40 individuals while they performed a simple computer task, making guesses to find or avoid a hidden target. The task stimuli implied three levels of reward probability and two levels of uncertainty. We found that reward probability level interacted with the trial search condition. That is, motor evoked potential (MEP) amplitude, a measure of corticospinal neuron excitability, increased with increasing reward probability when participants were instructed to “find” a target, but not when they were instructed to “avoid” a target. There was no effect of uncertainty on MEPs. Response times varied with the number of choices. A subset of participants also received paired-pulse stimulation to evaluate changes in short-intracortical inhibition (SICI). No effects of SICI were observed. Taken together, the results suggest that the reward-contingent modulation of M1 activity reflects reward probability or a related aspect of utility, not outcome uncertainty, and that this effect is sensitive to the conceptual framing of the task.

Withholding a Reward-driven Action: Studies of the Rise and Fall of Motor Activation and the Effect of Cognitive Depletion

“…2A). This shows that very early motor activity is influenced by the value of a reward-predicting stimulus, which is consistent with several previous studies (Klein, Olivier, & Duque, 2012; Klein-Flügge & Bestmann, 2012; Mooshagian, Keisler, Zimmermann, Schweickert, & Wassermann, 2015; Suzuki et al, 2014) 1 .…”

Does intrinsic motivation enhance motor cortex excitability?

“…Given the importance of these factors, it seems important to experimentally and/or statistically control for their influences in order to determine the role of the smaller cognitive influences. The absence of a difference between the types of motivational conditions (IM, EM, and NO) is not in accordance with previous findings, as several studies have reported that motivational inductions such as monetary incentives increased corticospinal excitability (i.e., increased MEP amplitude) (Gupta & Aron, 2011;Mooshagian et al, 2015). Not only did we not find greater MEP amplitude when comparing IM to EM, but we also did not find even a difference of these motivational conditions in comparison to the NO condition.…”

“…It has recently been demonstrated that corticospinal excitability is modulated by psychological inductions such as exposure to emotional stimuli (e.g., fearful faces) (e.g., Coombes et al, 2009;Hajcak et al, 2007;Schutter, Hofman, & Van Honk, 2008;van Loon, van den Wildenberg, van Stegeren, Hajcak, & Ridderinkhof, 2010). More recently, some studies have demonstrated that motivational inductions can also influence corticospinal excitability (Gupta & Aron, 2011;Kapogiannis, Campion, Grafman, & Wassermann, 2008;Klein, Olivier, & Duque, 2012;Mooshagian, Keisler, Zimmermann, Schweickert, & Wassermann, 2015;Thabit et al, 2011). However, all of these studies have triggered a form of EM by exposing their participants to rewards, and it remains to be determined if the activation of IM can lead to a differential state of corticospinal excitability.…”

Optimizing performance through intrinsic motivation and attention for learning: The OPTIMAL theory of motor learning

“…These, including the corticospinal tract, have been recently attributed to expectations (Arias, Robles-García, Espinosa, Corral-Bergantiños, Mordillo-Mateos, Grieve et al, 2014;Mooshagian, Keisler, Zimmermann, Schweickert, & Wassermann, 2015;van Elswijk, Kleine, Overeem, & Stegeman, 2007). Similarly, suppression of activity related to unanticipated response options has been found (Klein, Petitjean, Olivier, & Duque, 2014).…”