TEMPORAL SEGMENTATION AND MULTIPLE-SOURCE ANALYSIS OF SHORT-LATENCY MEDIAN NERVE SEPS

Short-latency (10-50 ms) median nerve somatosensory evoked potentials (SEPs) from four normal subjects were analysed by means of temporal se gmentation techniques and source derivation methods. In each case the responses were recorded using 32 electrodes. Dipolar optimization was carried out with a time-varying technique, using three different appro aches: regional sources estimation, spherical source estimation (one r adial and one tangential component), and multiple dipolar approach. Th is was to assess the relative influence on the dipolar solution of the different optimization techniques. The effect of the different number of channels in the estimation procedures has been also investigated. The methods of optimization are crucial, particularly for the orientat ion of P22. In all cases the source location estimated with the 32-ele ctrode montage was shifted towards the centre of the spheres.