Disconnecting force from money: effects of basal ganglia damage on incentive motivation

Abstract

Bilateral basal ganglia lesions have been reported to induce a particular form of apathy, termed auto-activation deficit (AAD), principally defined as a loss of self-driven behaviour that is reversible with external stimulation. We hypothesized that AAD reflects a dysfunction of incentive motivation, a process that translates an expected reward (or goal) into behavioural activation. To investigate this hypothesis, we designed a behavioural paradigm contrasting an instructed (externally driven) task, in which subjects have to produce different levels of force by squeezing a hand grip, to an incentive (self-driven) task, in which subjects can win, depending on their hand grip force, different amounts of money. Skin conductance was simultaneously measured to index affective evaluation of monetary incentives. Thirteen AAD patients with bilateral striato-pallidal lesions were compared to thirteen unmedicated patients with Parkinson's; disease (PD), which is characterized by striatal dopamine depletion and regularly associated with apathy. AAD patients did not differ from PD patients in terms of grip force response to external instructions or skin conductance response to monetary incentives. However, unlike PD patients, they failed to distinguish between monetary incentives in their grip force. We conclude that bilateral striato-pallidal damage specifically disconnects motor output from affective evaluation of potential rewards.

Get Aroused and Be Stronger: Emotional Facilitation of Physical Effort in the Human Brain

“…Behaviorally, we replicated previous findings that people, consciously or subconsciously, adapt their force according to incentive levels, whether it involves real or virtual money (Pessiglione et al, 2007;Schmidt et al, 2008). This would correspond to a trade-off between the required energy and the expected payoff.…”

“…To this end, we adapted our incentive force task, in which subjects must squeeze a hand grip to win money (Pessiglione et al, 2007;Schmidt et al, 2008). The amount of money at stake (0.01, 0.1, or 1€) was randomly varied on a trial-by-trial basis, and subjects were told that they would be allowed to keep a fraction of that monetary incentive, corresponding to the force produced.…”

Why Don't We Move Slower? The Value of Time in the Neural Control of Action

“…In addition, the striatum could play a critical role in MT because it has been shown to be related to the temporal discounting of reward (Kobayashi and Schultz, 2008). Therefore, valuation of MT could be partly encoded in that area as it is a fundamental center to gauge effortbenefit situations (Croxson et al, 2009) even in the absence of extrinsic reward (Schouppe et al, 2014). It would be the purpose of future studies to investigate the neural correlates of time cost variations arising from task modifications.…”

How emotion context modulates unconscious goal activation during motor force exertion

“…Investigating apathy is particularly intriguing given an important feature of this syndrome is that motor poverty can be reversed by strong external incentives (Levy and Dubois, 2006). Modulation of force output in rewarding contexts have been reported in healthy individuals with high apathy traits (Bonnelle et al, 2015), and after subcortical brain damage (Schmidt et al, 2008). Whether implicit effort priming with emotional or conceptual stimuli can facilitate behaviour and concomitant activity of the mesolimbic and frontostriatal circuits in individuals with behavioural or emotional apathy remains to be elucidated.…”

“…The maximum force reached and impulse (area under the curve) over the 3.5 s period of force production were determined for each trial and expressed as a percentage of MVC in order to eliminate individual differences in maximal force capacity (similar to other effort exertion studies; Cléry-Melin et al, 2011;Pessiglione et al, 2007;Schmidt et al, 2009;Schmidt et al, 2008;Schmidt et al, 2010). As the impulse and maximum force showed a similar pattern of results, we retained the latter to describe in the results below (see Figure S1 in Supplementary material).…”