Research Article

Experimental Brain Research

, Volume 194, Issue 2, pp 259-283

First online:

Velocity control in Parkinson’s disease: a quantitative analysis of isochrony in scribbling movements

  • Paolo VivianiAffiliated withFaculty of Psychology and Educational Sciences, University of Geneva Email author 
  • , Pierre R. BurkhardAffiliated withDepartment of Neurology, Faculty of Medicine, Geneva University Hospitals
  • , Sabina Catalano ChiuvéAffiliated withDepartment of Neurology, Neuropsychology Unit, Geneva University Hospitals
  • , Corrado Corradi dell’AcquaAffiliated withCognitive Neuroscience Sector
  • , Philippe VindrasAffiliated withLaboratory of Neurophysiology of Perception and Movement, Institute of Cognitive Science, CNRS UMR 5229

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An experiment was conducted to contrast the motor performance of three groups (N = 20) of participants: (1) patients with confirmed Parkinson Disease (PD) diagnose; (2) age-matched controls; (3) young adults. The task consisted of scribbling freely for 10 s within circular frames of different sizes. Comparison among groups focused on the relation between the figural elements of the trace (overall size and trace length) and the velocity of the drawing movements. Results were analysed within the framework of previous work on normal individuals showing that instantaneous velocity of drawing movements depends jointly on trace curvature (Two-thirds Power Law) and trace extent (Isochrony principle). The motor behaviour of PD patients exhibited all classical symptoms of the disease (reduced average velocity, reduced fluency, micrographia). At a coarse level of analysis both isochrony and the dependence of velocity on curvature, which are supposed to reflect cortical mechanisms, were spared in PD patients. Instead, significant differences with respects to the control groups emerged from an in-depth analysis of the velocity control suggesting that patients did not scale average velocity as effectively as controls. We factored out velocity control by distinguishing the influence of the broad context in which movement is planned—i.e. the size of the limiting frames—from the influence of the local context—i.e. the linear extent of the unit of motor action being executed. The balance between the two factors was found to be distinctively different in PD patients and controls. This difference is discussed in the light of current theorizing on the role of cortical and sub-cortical mechanisms in the aetiology of PD. We argue that the results are congruent with the notion that cortical mechanisms are responsible for generating a parametric template of the desired movement and the BG specify the actual spatio-temporal parameters through a multiplicative gain factor acting on both size and velocity.


Parkinson’s disease Movement control Isochrony Two-thirds Power Law