Increased bradykinesia in Parkinson’s disease with increased movement complexity: elbow flexion–extension movements

Abstract

The present research investigates factors contributing to bradykinesia in the control of simple and complex voluntary limb movement in Parkinson's disease (PD) patients. The functional scheme of the basal ganglia (BG)-thalamocortical circuit was described by a mathematical model based on the mean firing rates of BG nuclei. PD was simulated as a reduction in dopamine levels, and a loss of functional segregation between two competing motor modules. In order to compare model simulations with performed movements, flexion and extension at the elbow joint is taken as a test case. Results indicated that loss of segregation contributed to bradykinesia due to interference between competing modules and a reduced ability to suppress unwanted movements. Additionally, excessive neurotransmitter depletion is predicted as a possible mechanism for the increased difficulty in performing complex movements. The simulation results showed that the model is in qualitative agreement with the results from movement experiments on PD patients and healthy subjects. Furthermore, based on changes in the firing rate of BG nuclei, the model demonstrated that the effective mechanism of Deep Brain Stimulation (DBS) in STN may result from stimulation induced inhibition of STN, partial synaptic failure of efferent projections, or excitation of inhibitory afferent axons even though the underlying methods of action may be quite different for the different mechanisms.

Differential Beta-Band Event-Related Desynchronization during Categorical Action Sequence Planning

“…This leads to the speculation that the categorical action sequences used in the current study may have different preparation loads. And the different preparations may be due to movement complexity of sequences [39], [40]. However, in this study, the overall error rates among the three categories did not show statistical difference, and the movement onset latency among the three categories did not differ significantly either.…”

Standardized Handwriting to Assess Bradykinesia, Micrographia and Tremor in Parkinson's Disease

“…These four features were derived from data obtained during the writing tasks, which were more complex than the tracing tasks. Moroney et al [24] also showed in a simulation model that PD patients were slower than HC in both simple and complex movements, but slowness increased with increased movement complexity.…”

Motor automaticity in Parkinson's disease

“…Inadequate force of the initial impulsive activity in the agonist (Hallett and Khoshbin, 1980), and inappropriate scaling of the dynamic muscle force to the movement parameters (Berardelli et al, 1986) are some likely reasons. It has been suggested that the impaired basal ganglia-thalamo-cortical pathway results in decreased basal ganglia outputs, which in turn produces slowed movements (Contreras-Vidal and Stelmach, 1995; Moroney et al, 2008). An alternative explanation is that the slowness of movement in PD is due to inadequately activated motor cortical and spinal cord centers because of dopamine reduction not only in basal ganglia, but also in cortical and spinal sites (Cutsuridis, 2011).…”