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Perceptual musical functions were investigated in patients suffering from unilateral cerebrovascular cortical lesions. Using MIDI (Musical Instrument Digital Interface) technique, a standardized short test battery was established that covers local (analytical) as well as global perceptual mechanisms. These represent the principal cognitive strategies in melodic and temporal musical information processing (local, interval and rhythm; global, contour and metre). Of the participating brain-damaged patients, a total of 69% presented with post-lesional impairments in music perception. Left-hemisphere-damaged patients showed significant deficits in the discrimination of local as well as global structures in both melodic and temporal information processing. Right-hemisphere-damaged patients also revealed an overall impairment of music perception, reaching significance in the temporal conditions. Detailed analysis outlined a hierarchical organization, with an initial right-hemisphere recognition of contour and metre followed by identification of interval and rhythm via left-hemisphere subsystems. Patterns of dissociated and associated melodic and temporal deficits indicate autonomous, yet partially integrated neural subsystems underlying the processing of melodic and temporal stimuli. In conclusion, these data contradict a strong hemispheric specificity for music perception, but indicate cross-hemisphere, fragmented neural substrates underlying local and global musical information processing in the melodic and temporal dimensions. Due to the diverse profiles of neuropsychological deficits revealed in earlier investigations as well as in this study, individual aspects of musicality and musical behaviour very likely contribute to the definite formation of these widely distributed neural networks.

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The data are interpreted to indicate altered frontal inhibitory functions. Similarities and dissimilarities between the findings for TS and OCD are discussed with respect to other pathophysiologic aspects of the disorders.

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Tourette Syndrome (TS) has been related to hyperactive basal-ganglia thalamocortical pathways. This suggests that action monitoring might also be hyperactive. The present study used the event-related brain potential (ERP) technique to investigate this hypothesis. A simple "oddball" reaction time experiment was administered to a group of TS patients and a matched control group. In order to investigate variations in attentional allocation separate experimental runs were undertaken with target frequencies of 50% and 80%. The P3b component to targets was taken as an indicator of the target evaluation process and the response locked error-related negativity (ERN) served as an indicator of action monitoring. We hypothesized that the amplitudes of ERN and P3b would vary with respect to target frequency. The TS group would show an overall enhanced ERN but an unchanged P3b.ERN and P3b amplitudes were lower in the 80% target condition than in the 50% condition. In comparison with control subjects TS patients displayed an ERN of overall higher amplitude but with similar variations between target conditions. P3b amplitudes did not differ between groups. The data are interpreted to support the assumption of an abnormal action monitoring system in TS. A number of similarities to Obsessive-Compulsive Disorder are outlined and it is argued that the findings could be related to a hyperactive frontal-striatal-thalamic-frontal circuit.

Evoked potentials were recorded in three different visual experiments in 14 patients with amyotrophic lateral sclerosis (ALS) and 14 matched control subjects. Control subjects' evoked potentials (EPs) were characterized by an initial positivity in the 90-140 ms range (P1) at the temporo-occipital site. This component was absent from the group average of the ALS patients as well as the individual patients' EPs. As the P1 is known to emanate from inferior occipito-temporal areas, this finding provides electrophysiological evidence for a cortical involvement in ALS including visual areas.