Changes in the cortical components of the visual evoked potential with age in man

Pattern visual evoked potentials (PVEPs) were recorded from 177 normal subjects aged 11-87 years. The purpose was to determine age-dependent changes in the latency of the individual components of the waveform. The initial components of the PVEP, which are thought to reflect activity in the primary visual (striate) cortex, showed no change in latency from 11-50 years followed by an abrupt increase occurring during the sixth decade. It is probable that this delay in the PVEP is mediated largely by pathophysiological changes occurring either in the eye or visual pathways, or both. The secondary components of the PVEP, which are presumed to be generated in the visual association areas of the extrastriate cortex, showed a progressive although initially very limited increase in latency starting after adolescence. It is suggested that those delays occurring between 21 and 50 years in the secondary components are mediated largely by intracortical factors. The more pronounced delays occurring for the older age groups (over 50 years) appear to be caused by a combination of cortical, subcortical and ocular changes in visual function. The prolongation of the later components in the age group 11-20 years seems to reflect maturational changes almost entirely confined to intracortical processes. The results are discussed in terms of the many conflicting reports of the effects of age on the PVEP.