ABSTRACT
BACKGROUND: Multiple system atrophy (MSA) is an atypical parkinsonian syndrome including cerebellar impairment and poor response to levodopa. We assessed right hand motor activation in patients with MSA before and after an acute levodopa challenge in comparison with patients with PD and healthy volunteers (HVs). METHODS: Eighteen patients with MSA, 8 patients with PD, and 10 age-matched HVs were included. Regional cerebral blood flow measurements with H(2)(15)O PET were performed at rest and during a right hand movement. Statistical parametric mapping was used to analyze motor vs rest in OFF and ON conditions and the effect of levodopa on motor activation. RESULTS: Before levodopa, patients with MSA activated most known cerebral motor areas. Compared with HVs, patients with MSA exhibited less bilateral cerebellar activation and greater left superior parietal activation. They also had less bilateral cerebellar and greater supplementary motor and left superior parietal activation than patients with PD. Conversely, patients with PD had greater activation than HVs in the right cerebellum and less in the supplementary motor cortex. After levodopa, patients with MSA exhibited reduced activation in anterior cingulate, whereas patients with PD had greater activation in the right cerebellum. CONCLUSION: Patients with MSA and patients with PD recruited different motor networks. Patients with PD preferentially activated cerebellar pathways, possibly to compensate for basal ganglia dysfunction. This was not observed in patients with MSA, probably because of cerebellar dysfunction; other frontoparietal cortical areas were recruited.
Subject(s)
Movement/physiology , Multiple System Atrophy/diagnostic imaging , Multiple System Atrophy/physiopathology , Parkinson Disease/diagnostic imaging , Parkinson Disease/physiopathology , Aged , Brain Mapping , Case-Control Studies , Deuterium Oxide , Dopamine Agents/therapeutic use , Functional Laterality/drug effects , Functional Laterality/physiology , Hand/physiopathology , Humans , Levodopa/therapeutic use , Motor Cortex/diagnostic imaging , Movement/drug effects , Multiple System Atrophy/drug therapy , Multiple System Atrophy/pathology , Parkinson Disease/drug therapy , Parkinson Disease/pathology , Positron-Emission Tomography , Statistics, NonparametricABSTRACT
BACKGROUND: Some neuroimaging studies have suggested that specific right hemispheric regions can compensate deficits induced by left hemispheric lesions in vascular aphasia. In particular, the right inferior frontal cortex might take part in lexical retrieval in patients presenting left-sided lesions involving the homologous area. OBJECTIVE: To address whether the involvement of the right inferior frontal cortex is either unique to recovering aphasic patients or present also in other circumstances of enrichment of lexical abilities, i.e., in non-brain-damaged subjects over learning of new vocabulary. METHODS: Ten post-stroke aphasic patients experiencing word finding difficulties were intensively trained to retrieve object names in French over a 4-week period. Twenty healthy subjects were similarly trained to name these items in either Spanish or English, i.e., foreign languages that they learned at school but did not master. By analogy to aphasic patients, healthy subjects had to work out the phonetic/phonologic representations of long-acquired but forgotten words. Brain activity changes were assessed in two H(2)(15)O PET sessions involving picture naming tasks that were performed before and after training. RESULTS: Comparable post-training performance and changes in regional cerebral blood flow including mainly the right insular and inferior frontal regions were found in both groups. CONCLUSION: Our results suggest that enhanced activities in right-sided areas observed in recovering aphasia is not the mere consequence of damage to left-sided homologous areas and could reflect the neural correlates of lexical learning also observed in control subjects.
