SCALP TOPOGRAPHIC MAPPING OF MIDDLE-LATENCY SOMATOSENSORY-EVOKED POTENTIALS IN NORMAL AGING AND DEMENTIA

Middle-latency somatosensory evoked potentials (MLSEPs) were recorded in four groups of subjects: 13 normal young controls (mean age, 17.9 y ears), 11 normal elderly (mean age, 66.9 years), 11 patients with deme ntia of Alzheimer's type (DAT; mean age, 70.5), and four with vascular dementia (mean age, 79.3). MLSEPs in normal elderly showed an increas e in the latency of P22, N30, P45, N60, and P100, and in the amplitude of N60. DAT patients also presented such changes; however, the increa se in the amplitude of N60 was much more evident than that found in no rmal aging and was accompanied by a significant increase in amplitude of P45. Patients with vascular dementia tended to show longer latencie s and larger amplitudes than the other groups. The increase in amplitu de of P45 and N60 in MLSEPs seems to be characteristically associated with normal aging and the development of dementia. It is suggested tha t the mechanism of such functional changes might be correlated with th e structural and neurochemical changes accompanying neuronal loss in t hese conditions.