Levodopa-induced dyskinesias are disabling motor complications of long-term dopamine replacement in patients with Parkinson’s disease. In recent years, several alternative models have been proposed to explain the pathophysiological mechanisms underlying this hyperkinetic motor disorder. In particular, our group has shed new light on the role of the prefrontal cortex as a key site of interest, d...

Levodopa-induced dyskinesia is a major complication of long-term dopamine replacement therapy for Parkinson's disease that becomes increasingly problematic in advanced Parkinson's disease. Although the cause of levodopa-induced dyskinesias is still unclear, recent work in animal models of the corticostriatal system has suggested that levodopa-induced dyskinesias might result from abnormal contr...

The functional status of the globus pallidus internal segment (GPi) plays a key role in mediating the effects of antiparkinsonian drugs. During long-term levodopa therapy, patients develop abnormal movements, dyskinesias, the pathophysiological basis of which is poorly understood. We recorded single cells in the GPi of parkinsonian monkeys continuously through the "off" and "on" states, and 10 ...

Objective: To test the hypothesis that anosognosia-for-dyskinesias in Parkinson’s disease (PD) results from a failure to detect discrepancies between intended and actual movement. Background: PD patients often complain of drug-induced dyskinesias (involuntary movements) less than their carers. This remarkable unawareness is an example of anosognosia (i.e., unawareness of deficits associated wit...

Despite the importance and frequency of levodopa-induced dyskinesias, little is known about their causal mechanisms. In this study, electrophysiological single-unit recordings of the neuronal activity of the globus pallidus internalis (GPi), the main basal ganglia output structure, and the globus pallidus externalis (GPe) were recorded continuously in both normal and 1-methyl-4-phenyl-1,2,3,6-t...

Chronic thalamic stimulation was performed in 10 Parkinsonian patients with disabling tremor and poor response to drug therapy. During the stereotactic procedure, an electrode was introduced in the ventralis intermediate nucleus of the thalamus. Test stimulation was performed during the intra-operative procedure and a few days after surgery using an external stimulator. When tremor was obviousl...

BACKGROUND Abnormal involuntary movements (dyskinesias) are common in patients with Parkinson disease (PD) as a consequence of the disease and dopaminergic replacement therapy. Early morning off-medication choreic dyskinesias have been recently reported after fetal dopaminergic cell transplantations in patients with advanced PD. OBJECTIVE To determine the frequency and severity of the early m...

The aim of this work was to study the role of subthalamo-pallidal synchronisation in the pathophysiology of dyskinesias. We recorded local field potentials (LFPs) in a patient with Parkinson's disease and left surgery induced dyskinesias with double, bilateral deep brain stimulation electrode implants in the subthalamic nucleus (STN) and the globus pallidus internus (GPi). Synchronisation was s...

When l-dopa use began in the early 1960s for the treatment of Parkinson's disease, nausea and reversible dyskinesias were experienced as continuing side effects. Carbidopa or benserazide was added to l-dopa in 1975 solely to control nausea. Subsequent to the increasing use of carbidopa has been the recognition of irreversible dyskinesias, which have automatically been attributed to l-dopa. The ...