Abstract
In order to discuss whether somatosensory evoked response (SER) and contingent negative variation (CNV) are suitable indicators of the aging process, SER to mechanical stimulation and CNV, as well as electroencephalography (EEG) and inteligence scales, were performed on the healthy aged adults. Subjects are the 41 aged adults of 61-80 years (12 males and 29 females) who participate in lesson programs of Osaka Prefectural Center for the aged. For the recording of SERs, tapping stimuli are applied on the right palm by a pulse generator. The paradigm for eliciting the CNV consists of a warning signal (S1) followed by an imperative signal (S2) to which the subjects make a motor response (MR). The CNV appears as a surface-negative shift of potential when 15 responses are summated. The results are summarised as follows. 1. The mean score of Hasegawa's dementia rating scale (HDRS) exercised for the 41 aged adults was 30.9 ranging from 23 to 32.5. The mean IQ of Kohs's blocking design test (KBDT) was 87.3 ranging from 45 to 124. 2. Abnormal EEG was observed in 7 subjects (17.1%) of the 41 aged adults, while normal EEG was observed in 26 subjects (63.4%). Normal SERs were observed in 28 subjects of the 41 aged adults, and peak latencies of SER were abnormally prolonged in 11 subjects of them. On the other hand, peaks of SERs were absent in only 2 of them. The atypical type of CNV was observed in 7 subjects of the 41 aged adults, and then PINV (post imperative negative variation), which is defined as the delayed base line return of CNV after S2, was also observed in 7 subjects of them. 3. From the results of clinical neuropsychiatric examination, intelligence scales and electroencephalographic findings, we selected the 29 normal aged out of the 41 aged adults, and then discussed the results of SER and CNV in the 29 normals. The mean latencies of P2, N2 and P3 peaks in SERs were not influenced by the aging process. But the mean latency of N3 peak in SER was 69.0msec in 60's, 70.9msec in 70's, and this mean value was much higher than that (62.5msec) in the 48 normal adults (mean age 31.5 year; ranging from 19 to 50). In conclusion, it is considered that the latency of N3 peak in SER is a suitable indicator of the aging process. There was little difference in the morphology and the amplitude of CNV between the normal adults and the normal aged. PINV, which was often observed in the demented aged, did not appear in the normal aged nearly. It is considered that the appearance of PINV is probably a suitable indicator of the dementing process.
