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Article Dans Une Revue European Journal of Neuroscience Année : 2001

Stereotactic recordings of median nerve somatosensory-evoked potentials in the human pre-supplementary motor area

Résumé

Median nerve somatosensory-evoked potentials (SEPs) have been recorded using intracortical electrodes stereotactically implanted in the frontal lobe of eight epileptic patients in order to assess the waveforms, latencies and surface-to-depth distributions of somatosensory responses generated in the anterior subdivision of supplementary motor areas (SMAs), the so-called pre-SMA. Intracortical responses were analysed in two latency ranges: 0--50 ms and 50--150 ms after stimulus. In all patients, we recorded in the first 50 ms after stimulus two positive P14 and P20 potentials followed by a N30 negativity. In the hemisphere contralateral to stimulation, the P20--N30 potentials showed a clear amplitude decrease from the outer to the inner aspect of the frontal lobe with minimal amplitudes in the pre-SMA. In the hemisphere ipsilateral to stimulus, P20 and N30 amplitudes were decreasing from mesial to lateral frontal cortex. In the 50--150 ms latency range, contacts implanted in the pre-SMA recorded a negative potential in the 60--70 ms latency range which, in five patients, was followed by a positive response peaking 80--110 ms after stimulus. These potentials were not picked up by more superficial contacts. We conclude that no early SEP is generated in pre-SMA in the first 50 ms after stimulation, while some potentials peaking in the 60--100 ms after stimulus are likely to originate from this cortical area. The latency of the pre-SMA responses recorded in our patients supports the hypothesis that the pre-SMA does not receive short-latency somatosensory inputs via direct thalamocortical projections. More probably the pre-SMA receives somatosensory inputs mediated by a polysynaptic transcortical transmission through functionally secondary motor and somatosensory areas.

Dates et versions

hal-02472383 , version 1 (10-02-2020)

Identifiants

Citer

Carmen Barba, Maud Frot, Marc Guenot, François Mauguiere. Stereotactic recordings of median nerve somatosensory-evoked potentials in the human pre-supplementary motor area. European Journal of Neuroscience, 2001, 13 (2), pp.347-356. ⟨10.1046/j.0953-816x.2000.01393.x⟩. ⟨hal-02472383⟩
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