Synergic control of action in levodopa-naïve Parkinson’s disease patients: I. Multi-finger interaction and coordination

Paulo B. de Freitas, Sandra M.S.F. Freitas, Sasha Reschechtko, Tyler Corson, Mechelle M. Lewis, Xuemei Huang, Mark L. Latash

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We explored the origin of the impaired control of action stability in Parkinson’s disease (PD) by testing levodopa-naïve PD patients to disambiguate effects of PD from possible effects of long-term exposure to levodopa. Thirteen levodopa-naïve PD patients and 13 controls performed single- and multi-finger force production tasks, including producing a self-paced quick force pulse into a target. A subgroup of patients (n = 10) was re-tested about 1 h after the first dose of levodopa. Compared to controls, PD patients showed lower maximal forces and synergy indices stabilizing total force (reflecting the higher inter-trial variance component affecting total force). In addition, PD patients showed a trend toward shorter anticipatory synergy adjustments (a drop in the synergy index in preparation to a quick action) and larger non-motor equivalent finger force deviations. Lower maximal force, higher unintentional force production (enslaving) and higher inter-trial variance indices occurred in PD patients after one dosage of levodopa. We conclude that impairment in synergies is present in levodopa-naïve patients, mainly in indices reflecting stability (synergy index), but not agility (anticipatory synergy adjustments). A single dose of levodopa, however, did not improve synergy indices, as it did in PD patients on chronic anti-PD medication, suggesting a different mechanism of action. The results suggest that indices of force-stabilizing synergies may be used as an early behavioral sign of PD, although it may not be sensitive to acute drug effects in drug-naïve patients.

Original languageEnglish (US)
Pages (from-to)229-245
Number of pages17
JournalExperimental Brain Research
Issue number1
StatePublished - Jan 1 2020

All Science Journal Classification (ASJC) codes

  • General Neuroscience


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