Dopamine promotes instrumental motivation, but reduces reward-related vigour

Abstract

We can be motivated when reward depends on performance, or merely by the prospect of a guaranteed reward. Performance-dependent (contingent) reward is instrumental, relying on an internal action-outcome model, whereas motivation by guaranteed reward may minimise opportunity cost in reward-rich environments. Competing theories propose that each type of motivation should be dependent on dopaminergic activity. We contrasted these two types of motivation with a rewarded saccade task, in patients with Parkinson’s disease (PD). When PD patients were ON dopamine, they had greater response vigour (peak saccadic velocity residuals) for contingent rewards, whereas when PD patients were OFF medication, they had greater vigour for guaranteed rewards. These results support the view that reward expectation and contingency drive distinct motivational processes, and can be dissociated by manipulating dopaminergic activity. We posit that dopamine promotes goal-directed motivation, but dampens reward-driven vigour, contradictory to the prediction that increased tonic dopamine amplifies reward expectation

The effect of subliminal incentives on goal-directed eye movements

“…This latter mechanism may need a finer, moment-to-moment adjustment of saccade parameters and perhaps a larger involvement of the supervisory cortical network involved in the goal-directed planning of eye movements that is achieved at a higher level of conscious awareness. Such a mechanism can explain the larger effect sizes found for the effect of subliminal rewards on the saccade frequency compared to the peak velocity/vigor, which is in line with previous studies showing differences between the motivational enhancement of saccadic speed versus vigor ( 47 , 48 ), but also entails that at a certain level of conscious awareness of reward incentives both saccadic parameters may be simultaneously influenced. The behavioral paradigm devised here can be employed in future neurophysiological and neuroimaging studies to unravel the balance between subcortical and cortical mechanisms involved in the subliminal motivational modulation of eye movements.…”

Reward boosts reinforcement-based motor learning

“…Moreover, subjects were distributed in three groups where training involved sensory (S) feedback only (Group -S ; n = 30), sensory and reinforcement (SR) feedback (Group -SR ; n = 30), or both feedbacks and a reward (SRR, Group -SRR ; n = 30). Monetary gains were used as they are known to strongly modulate the motivation to engage in various tasks (Grogan et al, 2020a(Grogan et al, , 2020bManohar et al, 2015;Schultz, 2015;Shadmehr et al, 2019). We investigated how participants learned and maintained the skill depending on the type of feedback experienced during training.…”

Muscarinic receptors mediate motivation via preparatory neural activity in humans

“…The CNV has been linked to activity in the thalamus, supplementary motor area, cingulate and ventral striatum (Nagai et al, 2004;Plichta et al, 2013), and to a range of neurotransmitters including dopamine (Linssen et al, 2011) which also modulates motivational effects on vigour (Grogan et al, 2020;Manohar & Husain, 2015). M1r activation in the striatum can modulate the excitability of indirect and direct pathways (Galarraga et al, 1999;Shen, Hamilton, Nathanson, & Surmeier, 2005), and increase dopamine release (de Klippel, Sarre, Ebinger, & Michotte, 1993), which are potential mechanisms for muscarinic motivation in humans.…”

“…Saccades with peak velocities outside 50-1600°s -1 were excluded. Saccadic velocity is correlated with the amplitude of the saccade, an effect known as the main sequence (Bahill, Clark, & Stark, 1975), and saccade amplitude can also be affected by reward (Grogan, Sandhu, Hu, & Manohar, 2020). To remove the effect of amplitude on velocity, we regressed peak velocity against amplitude within each participant and session, and took the residual peak velocity as our main measure (Figure 1c).…”

“…This reflects the difference between the velocity measured and the velocity predicted by the main sequence, with positive values meaning faster than expected velocity. This measure has previously been shown to be most sensitive to reward manipulations of vigour (Blundell et al, 2018;Grogan et al, 2020;Manohar, Finzi, Drew, & Husain, 2017;Manohar, Muhammed, Fallon, & Husain, 2019).…”