pubmed.ncbi.nlm.nih.gov

The effect of motivation on movement: a study of bradykinesia in Parkinson's disease - PubMed

The effect of motivation on movement: a study of bradykinesia in Parkinson's disease

Tamara Shiner et al. PLoS One. 2012.

Abstract

Background: Bradykinesia is a cardinal feature of Parkinson's disease (PD). Despite its disabling impact, the precise cause of this symptom remains elusive. Recent thinking suggests that bradykinesia may be more than simply a manifestation of motor slowness, and may in part reflect a specific deficit in the operation of motivational vigour in the striatum. In this paper we test the hypothesis that movement time in PD can be modulated by the specific nature of the motivational salience of possible action-outcomes.

Methodology/principal findings: We developed a novel movement time paradigm involving winnable rewards and avoidable painful electrical stimuli. The faster the subjects performed an action the more likely they were to win money (in appetitive blocks) or to avoid a painful shock (in aversive blocks). We compared PD patients when OFF dopaminergic medication with controls. Our key finding is that PD patients OFF dopaminergic medication move faster to avoid aversive outcomes (painful electric shocks) than to reap rewarding outcomes (winning money) and, unlike controls, do not speed up in the current trial having failed to win money in the previous one. We also demonstrate that sensitivity to distracting stimuli is valence specific.

Conclusions/significance: We suggest this pattern of results can be explained in terms of low dopamine levels in the Parkinsonian state leading to an insensitivity to appetitive outcomes, and thus an inability to modulate movement speed in the face of rewards. By comparison, sensitivity to aversive stimuli is relatively spared. Our findings point to a rarely described property of bradykinesia in PD, namely its selective regulation by everyday outcomes.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have the following competing interests: KP Bhatia received funding for travel from GlaxoSmithKline, Orion Corporation, Ipsen, and Merz Pharmaceuticals, LLC; serves on the editorial boards of Movement Disorders and Therapeutic Advances in Neurological Disorders; receives royalties from the publication of Oxford Specialist Handbook of Parkinson’s Disease and Other Movement Disorders (Oxford University Press, 2008); received speaker honoraria from GlaxoSmithKline, Ipsen, Merz Pharmaceuticals, LLC, and Sun Pharmaceutical Industries Ltd.; personal compensation for scientific advisory board for GSK and Boehringer Ingelheim; received research support from Ipsen. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Figure 1
Figure 1. Schematic of the movement time task.

Trial types are illustrated as a function of outcome valence (yellow for money trials and blue for shock trials) and presence or absence of a distractor (green flashing square). There were two possible outcomes in the money trials; ‘you have won 10 p’ or ‘you have not won 10 p’ and there were two possible outcomes for the shock trials; ‘you will now receive a shock’ or ‘you will now not receive a shock’. Subjects were exposed to 4 distinct trial types (see methods for details) comprising (i) money trial without distractor, (ii) money trial with distractor, (iii) shock trial without distractor, (iv) shock trial with distractor.

Figure 2
Figure 2. (A) Average movement times.

Average movement times (MT) (in ms) collapsed across money and shock trials for controls (white bars) and patients (grey bars). Error bars represent (two times) the s.e.m. (B) Average movement times in money and shock trials. Average movement times in money and shock trials for controls (white bars) and patients (grey bars). Error bars represent (two times) the s.e.m. (C) Money MT minus shock MT. Differences in movement time in money compared with shock trials. Plotted is the difference in movement times (ms) in money trials minus movement time in shock trials for controls (white bars) and patients (grey bars). Error bars represent (two times) the standard error of the difference.

Figure 3
Figure 3. Distractor MT minus no distractor MT.

Plotted is the difference in movement time (ms) in trials with a distractor present minus movement time in trials with no distractor present, for money trials and shock trials separately. Controls are represented by white bars and patients by grey bars. Error bars represent (two times) the standard error of the difference.

Similar articles

Cited by

References

    1. Edwards MQ N, Bhatia K (2008) Parkinson’s disease and other movement disorders. Oxford University Press.
    1. Montgomery EB Jr, Nuessen J (1990) The movement speed/accuracy operator in Parkinson’s disease. Neurology 40: 269–272. - PubMed
    1. Sheridan MR, Flowers KA (1990) Movement variability and bradykinesia in Parkinson’s disease. Brain 113 (Pt 4): 1149–1161. - PubMed
    1. Teasdale N, Phillips J, Stelmach GE (1990) Temporal movement control in patients with Parkinson’s disease. J Neurol Neurosurg Psychiatry 53: 862–868. - PMC - PubMed
    1. Hallett M, Khoshbin S (1980) A physiological mechanism of bradykinesia. Brain 103: 301–314. - PubMed

Publication types

MeSH terms