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Chapter 11
Neural Network Modeling of Voluntary
Single-Joint Movement Organization II.
Parkinson's Disease
Vassilis Cutsuridis
Abstract
The organization of voluntary movement is disrupted in Parkinson's dis-
ease. The neural network models of voluntary movement preparation and execu-
tion presented in the previous chapter are extended here by studying the effects of
dopamine depletion in the output of the basal ganglia and in key neuronal types in
the cortex and spinal cord. The resulting extended DA-VITE-FLETE model offers
an integrative perspective on corticospinal control of Parkinsonian voluntary move-
ment. The model accounts for most of the known empirical signatures of Parkinso-
nian willful action.
11.1 Introduction
Parkinson's disease (PD) is a disabling motor disorder that affects all kinds of
movements. In the early stages of PD, patients have difficulty with walking, speak-
ing, or getting in and out of chairs [33]. As the disease progresses, all move-
ments are affected resulting at the end of the disease a complete inability to
move. Patients require intense concentration to overcome the apparent inertia of the
limbs that exists even for the simplest motor tasks. Movement initiation is partic-
ularly impaired when novel movements or sequences of movements are attempted
[16, 3, 41].
The lack of understanding of the causes of PD and the problems associated with
its treatment have led to the search for appropriate animal models. Over the years,
two experimental methods have been employed to induce Parkinsonism in animals:
(1) application of reserpine, alpha-methyl-p-tyrosine (AMPT) [14], and 1-methyl-
4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) [12] resulting in dopamine depletion
in the brain and (2) stereotaxic lesions with focal injections of 6-hydroxydopamine
