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Background and Purpose: Abnormalities of finger representations in the somatosensory cortex have been identified in patients with focal hand dystonia. Measuring blood flow with positron emission tomography (PET) can be use to demonstrate functional localization of receptive fields. Methods: A vibratory stimulus was applied to the right thumb and little finger of six healthy volunteers and six patients with focal hand dystonia to map their receptive fields using H215O PET. Results: The cortical finger representations in the primary somatosensory cortex were closer to each other in patients than in normal subjects. No abnormalities were found in secondary somatosensory cortex, but the somatotopy there is less well distinguished. Conclusions: These data confirm prior electrophysiological and functional neuroimaging observations showing abnormalities of finger representations in somatosensory cortex of patients with focal hand dystonia.

We sought to determine how the pattern of cerebral activation, and in particular in frontal motor areas, during the performance of conditional motor tasks is dependent upon the modality of instruction (visual, auditory, or somatosensory). Regional cerebral blood flow (rCBF) changes with externally instructed movements were also compared with internally generated, self-paced, movements. We used positron emission tomography (PET) with the tracer H215O to measure rCBF in 22 healthy volunteers. External stimuli consisted of the randomized presentation of single or double impulses using a single modality for each condition. In the movement scans, the subjects used the index and middle fingers of their right hands to press a left button for a single and a right button for a double impulse, respectively. In the control scans, subjects were required to covertly distinguish a single from a double stimulus without a motor response. Data were analyzed using conventional subtraction techniques with a statistical threshold of Z > 2.33 with corrections for multiple comparisons. When the activation differences between the three externally instructed movement conditions were statistically compared, nonsignificant trends toward increased rCBF in the sensory cortex of the modality of the cue were observed but no differential activity in cortical motor areas. Internally generated movements, when compared to externally triggered movements, were associated with enhanced activation in bilateral medial and lateral premotor, dorsolateral prefrontal and superior parietal regions, largely confirming previous reports. The data indicate that, on a regional level, modality-specific processing in a conditional motor task does not occur in frontal motor areas and is probably confined to sensory areas.

Abnormalities of the sensory system have been proposed as causative factors for dystonia. By mapping the human cortical hand somatosensory area of 6 patients with focal dystonia of the hand, we found an abnormality of the normal homuncular organization of the finger representations in the primary somatosensory cortex (S1). Although a remote antecedent event or even a developmental anomaly cannot entirely be ruled out, our findings may support the concept that abnormal plasticity is involved in the development of dystonia.

Deiber, M.-P., S. P. Wise, M. Honda, M. J. Catalan, J. Grafman, and M. Hallett. Frontal and parietal networks for conditional motor learning: a positron emission tomography study. J. Neurophysiol. 78: 977–991, 1997. Studies on nonhuman primates show that the premotor (PM) and prefrontal (PF) areas are necessary for the arbitrary mapping of a set of stimuli onto a set of responses. However, positron emission tomography (PET) measurements of regional cerebral blood flow (rCBF) in human subjects have failed to reveal the predicted rCBF changes during such behavior. We therefore studied rCBF while subjects learned two arbitrary mapping tasks. In the conditional motor task, visual stimuli instructed which of four directions to move a joystick (with the right, dominant hand). In the evaluation task, subjects moved the joystick in a predetermined direction to report whether an arrow pointed in the direction associated with a given stimulus. For both tasks there were three rules: for the nonspatial rule, the pattern within each stimulus determined the correct direction; for the spatial rule, the location of the stimulus did so; and for the fixed-response rule, movement direction was constant regardless of the pattern or its location. For the nonspatial rule, performance of the evaluation task led to a learning-related increase in rCBF in a caudal and ventral part of the premotor cortex (PMvc, area 6), bilaterally, as well as in the putamen and a cingulate motor area (CM, area 24) of the left hemisphere. Decreases in rCBF were observed in several areas: the left ventro-orbital prefrontal cortex (PFv, area 47/12), the left lateral cerebellar hemisphere, and, in the right hemisphere, a dorsal and rostral aspect of PM (PMdr, area 6), dorsal PF (PFd, area 9), and the posterior parietal cortex (area 39/40). During performance of the conditional motor task, there was only a decrease in the parietal area. For the spatial rule, no rCBF change reached significance for the evaluation task, but in the conditional motor task, a ventral and rostral premotor region (PMvr, area 6), the dorsolateral prefrontal cortex (PFdl, area 46), and the posterior parietal cortex (area 39/40) showed decreasing rCBF during learning, all in the right hemisphere. These data confirm the predicted rCBF changes in premotor and prefrontal areas during arbitrary mapping tasks and suggest that a broad frontoparietal network may show decreased synaptic activity as arbitrary rules become more familiar.

There are limited data in terms of the clinical profile of Parkinson's disease in sub-Saharan African patients.To compare the clinical profile and access to standard antiparkinsonian therapies of a Cameroonian cohort of patients with an age, sex, and disease duration-matched Spanish cohort (Longitudinal Study of Parkinson's disease, ELEP).Observational, cross-sectional design. Demographic data were collected and the following ELEP assessments were applied: Scales for Outcomes in Parkinson's disease (SCOPA) Motor, Autonomic, Cognition, Sleep and Psychosocial; Hoehn and Yahr staging; modified Parkinson Psychosis Rating Scale; Cumulative Illness Rating Scale-Geriatrics; Hospital Anxiety and Depression Scale; pain and fatigue visual analog scales; Zarit, and EuroQoL.74 patients with idiopathic Parkinson's disease were included (37 from each country) with a mean age of 64.4±10.5 years old, 70.3% males, and mean disease duration of 5.6±5.9 years. Compared to the Spanish cohort, Cameroonians were intermittently treated, less frequently received dopaminergic agonists (p0.001), had a trend for taking lower doses of levodopa (p=0.06), and were more frequently on anticholinergics (p0.0005). Cameroonians were more severely impaired in terms of motor (Hoehn Yahr stage, p=0.03; SCOPA-Motor, p0.001), cognitive status (p0.001), anxiety and depression (p0.001), psychosis (p=0.008), somnolence, fatigue and pain (p0.001, respectively), caregiver burden (p0.0001), and quality of life (p=0.002). Instead, autonomic, comorbidity, and nocturnal sleep problems were similarly found.Limited and intermittent access to dopaminergic drugs has a negative impact on motor symptoms, nonmotor symptoms and quality of life in patients with Parkinson's disease and their caregivers.

To study the difficulty that patients with Parkinson's disease have in performing long sequential movements, we used H2(15)O PET to assess the regional cerebral blood flow (rCBF) associated with the performance of simple repetitive movements, well-learned sequential finger movements of varying length and self-selected movements. Sequential finger movements in the Parkinson's disease patients were associated with an activation pattern similar to that found in normal subjects, but Parkinson's disease patients showed relative overactivity in the precuneus, premotor and parietal cortices. Increasing the complexity of movements resulted in increased rCBF in the premotor and parietal cortices of normal subjects; the Parkinson's disease patients showed greater increases in these same regions and had additional significant increases in the anterior supplementary motor area (SMA)/cingulate. Performance of self-selected movements induced significant activation of the anterior SMA/cingulate in normal subjects but not in Parkinson's disease patients. We conclude that in Parkinson's disease patients more cortical areas are recruited to perform sequential finger movements; this may be the result of increasing corticocortical activity to compensate for striatal dysfunction.

The brain regions activated by simple repetitive and sequential finger movements of different length were localized by measuring regional cerebral blood flow (rCBF) with PET. The experimental design consisted of finger movements cued by auditory pacing at 0.5 Hz. In all conditions of different sequence length the contralateral primary sensorimotor and premotor cortex, supplementary motor area and ipsilateral cerebellar cortex were activated. These areas showed a large increase in activation from rest to simple repetitive movement, and a further increase with the shortest sequence, suggesting an executive role in running sequences. The ipsilateral premotor area (Brodmann area 6), bilateral posterior parietal areas (Brodmann area 7) and precuneus showed an increase in rCBF related only to the length of the sequences, without any change from rest to simple repetitive movement. These areas are more selectively related to sequence performance. This finding is consistent with the hypothesis that these areas function in the storage of motor sequences in spatial working memory. Our results suggest that sequential finger movements recruit discrete sets of brain areas with different functions.