Somatosensory-evoked potentials and slow oscillations in patients with cerebral lesions

Somatosensory-evoked potentials induced by electrical stimulation of the median nerve were recorded in patients with intracerebral lesions and in normal controls and were studied by means of spectral analysis. The results shown that (1) there is a statistically-significant difference between spectral distributions obtained from normal subjects and those obtained from patients; (2) whereas in normal subjects, specific frequency components of the spectrum are enhanced (are "driven") at specific frequencies of stimulation, in patients with cerebral pathology, such driving is completely or partially abolished; and (3) these differences between normal subjects and patients become more evident at frequencies of stimulation that may vary from one patient to another; for this reason it is suggested that the use of a fairly wide range of frequencies of stimulation may be of great importance when such methods are employed in the evaluation of the functional state of the brain.