STATISTICAL-ANALYSIS OF TOPOGRAPHIC MAPS OF SHORT-LATENCY SOMATOSENSORY-EVOKED POTENTIALS IN NORMAL AND PARKINSONIAN SUBJECTS

This work had the following objectives: i) to integrate temporal analy sis (N30 peak) with power-spectrum topographic mapping of short-latenc y somatosensory evoked potentials (SEP's) recorded in parkinsonian and normal control subjects; and ii) to analyze with a new statistical ap proach the between-group topographical differences in both the time an d frequency domains. The principal aim was to better determine the top ography of the scalp frontal areas where the amplitude of the N30 wave was previously found to be significantly reduced in parkinsonians. Th e statistical procedure was based on the combined use of descriptive d ata analysis (DDA) and multivariate analysis. In the context of DDA, a n improved version of significance probability mapping (SPM) was used by which it is possible to evaluate homo- and nonhomoscedastic data wi th parametric tests. The statistical evaluation of between-group diffe rences was performed with the multivariate Hotelling's T-2 test and th e associated post hoc test. With this statistical procedure, it was po ssible to determine that the between-group statistical differences in both the temporal and power spectrum distributions were localized only in midline and contiguous contralateral frontal areas of the scalp.