Quantitative analysis of neurophysiological processes of the aging CNS.

Electrophysiological studies were performed on 65 aged subjects (62--91 years) and 48 control subjects (18--38 years). The power spectrum of the EEG in the aging persons shows different types, from spectra with a marked peak of alpha activity to spectra of a desynchronized type. Progressive deterioration of the periodicity of the occipital alpha rhythm and also a progressive time shift between the activities of both occipital lobes were found in the aging subjects. The SEP and VEP have prolonged latencies of all components. The amplitudes of all components of the SEP are significantly increased and those of the VEP are within normal limits. There is a more significant involvement of the dominant hemisphere. Transcallosal transmission of the SEP is qualitatively not involved. Quantitatively there is a marked prolongation of the duration of the transmission of certain SEP components. Transmission of the SEP from the specific cortical response area to different areas of the ipsilateral hemisphere is significantly increased. It is assumed that during aging there is an involvement of the cortical neuronal transmitter mechanisms and a progressive decrease of the specific cortical inhibitory processes.