Functional MRI/event-related potential study of sensory consonance and dissonance in musicians and nonmusicians.

Pleasurability of individual chords, known as sensory consonance, is widely regarded as physiologically determined and has been shown to be associated with differential activity in the auditory cortex and in several other regions. Here, we present results obtained contrasting isolated four-note chords classified as consonant or dissonant in tonal music. Using event-related functional MRI, consonant chords were found to elicit a larger haemodynamic response in the inferior and middle frontal gyri, premotor cortex and inferior parietal lobule. The effect was right lateralized for nonmusicians and less asymmetric for musicians. Using event-related potentials, the degree of sensory consonance was found to modulate the amplitude of the P1 in both groups and of the N2 in musicians only.

Spatial correspondence between functional MRI (fMRI) activations and cortical current density maps of event-related potentials (ERP): a study with four tasks.

We investigated the spatial correspondence between functional MRI (fMRI) activations and cortical current density maps of event-related potentials (ERPs) reconstructed without fMRI priors. The presence of a significant spatial correspondence is a prerequisite for direct integration of the two modalities, enabling to combine the high spatial resolution of fMRI with the high temporal resolution of ERPs. Four separate tasks were employed: visual stimulation with a pattern-reversal chequerboard, recognition of images of nameable objects, recognition of written words, and auditory stimulation with a piano note. ERPs were acquired with 19 recording channels, and source localisation was performed using a realistic head model, a standard cortical mesh and the multiple sparse priors method. Spatial correspondence was evaluated at group level over 10 subjects, by means of a voxel-by-voxel test and a test on the distribution of local maxima. Although not complete, it was significant for the visual stimulation task, image and word recognition tasks (P < 0.001 for both types of test), but not for the auditory stimulation task. These findings indicate that partial but significant spatial correspondence between the two modalities can be found even with a small number of channels, for three of the four tasks employed. Absence of correspondence for the auditory stimulation task was caused by the unfavourable situation of the activated cortex being perpendicular to the overlying scalp, whose consequences were exacerbated by the small number of channels. The present study corroborates existing literature in this field, and may be of particular relevance to those interested in combining fMRI with ERPs acquired with the standard 10-20 system.

A neurophysiological study of myoclonus in patients with DYT11 myoclonus-dystonia syndrome.

Mutations in the epsilon-sarcoglycan (SGCE) gene have been associated with DYT11 myoclonus-dystonia syndrome (MDS). The aim of this study was to characterize myoclonus in 9 patients with DYT11-MDS presenting with predominant myoclonus and mild dystonia by means of neurophysiological techniques. Variously severe multifocal myoclonus occurred in all of the patients, and included short (mean 89.1 +/- 13.3 milliseconds) electromyographic bursts without any electroencephalographic correlate, sometimes presenting a pseudo-rhythmic course. Massive jerks could be evoked by sudden stimuli in 5 patients, showing a "startle-like" muscle spreading and latencies consistent with a brainstem origin. Somatosensory evoked potentials and long-loop reflexes were normal, as was silent period and long-term intracortical inhibition evaluated by means of transcranial magnetic stimulation; however, short-term intracortical inhibition revealed subtle impairment, and event-related synchronization (ERS) in the beta band was delayed. Blink reflex recovery was strongly enhanced. Myoclonus in DYT11-MDS seems to be generated at subcortical level, and possibly involves basal ganglia and brainstem circuitries. Cortical impairment may depend from subcortical dysfunction, but it can also have a role in influencing the myoclonic presentation. The wide distribution of the defective SCGE in DYT11-MDS may justify the involvement of different brain areas.