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Patients with Parkinson's disease show unbalanced capability to manage self-paced vs externally driven movements, or automatic-associated movements with respect to the intended voluntary movements. We studied the effect of a selective loss of dopaminergic terminals within the striatum and the execution of a well-learned set-shifting task as revealed using tyrosine hydroxylase immunoreactivity and magnetic resonance imaging in the rat. We found that, both in the externally cued condition, and in the externally-internally driven switching task, the cue-dependent constraints interfered with motor readiness in over training condition. The unilateral dopaminergic striatal depletion enhanced the switch-induced performance differences in favour of the internally-externally cued transition. Dopamine depleted rats, in fact, were impaired to produce an alternative motion when task switching required to change from an over trained behaviour, towards an alternative self-paced response. The comparative analysis of behavioural, tyrosine hydroxylase immunoreactivity and magnetic resonance imaging data, revealed a shrinkage of the lesioned striatum, and an enlargement of the ipsilateral ventricle that could provide useful markers for monitoring pathological changes occurring during early stages of Parkinson's disease in vivo., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Jaw movements are severely affected in Parkinson's disease. Deep brain stimulation (DBS) of basal ganglia targets is known to ameliorate oromotor control. In this study, we examined the effects of DBS of the pedunculopontine tegmental nucleus (PPTg) on jaw movements in selected parkinsonian patients., Methods: The effects of low-frequency (25 Hz) stimulation of the PPTg on jaw movements were investigated through electrognathographic analysis in parkinsonian patients who were selected for PPTg stimulation. Changes in jaw velocity and amplitude during voluntary opening and closing movements of the mouth, as well as the maximum frequency of self-paced sequences of opening and closing cycles, were analyzed., Results: Low-frequency stimulation of the PPTg in the OFF-drugs condition significantly improved the opening and closing velocities, vertical amplitude and rhythm of voluntary movements. In some instances, movement parameters during stimulation were within the range of those recorded in healthy controls., Discussion: This is the first study investigating the impact of PPTg DBS on oromotor control in parkinsonian patients. The results show that jaw movements may be restored under stimulation and suggest that the pedunculopontine nucleus may play a key role in controlling oromotor activity., (Copyright © 2012 Elsevier Inc. All rights reserved.)