The effects of aging on selective attention to touch: a reduced inhibitory control in elderly subjects?

This article aimed at disclosing differences in the brain mechanisms underlying selective attention between elderly and young subjects. We studied two populations of subjects, 17 elderly (mean age: 71.7) and 12 young (mean age: 26.9). Somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded from 19 scalp electrodes in a neutral condition (NC), in which subjects were asked to disregard the electrical stimulation and in a selective attention condition (SAC), in which the subjects had to count tactile stimuli delivered on the same hand of the stimulated median nerve. In a further 3 old and in 3 young subjects, SEPs were recorded also in a distraction condition (DC), in which the subjects had to perform a mathematical task. The SEP amplitude increase during SAC was lower in old than in young subjects. Moreover, while in young subjects the N140 potential was identifiable only in SAC, in the elderly population it was already evoked during both NC and DC. Elderly subjects are probably unable to divert their attention from the median nerve electric stimuli during NC and DC and, therefore, have lower attention resources to invest during SAC. This may explain the recording of the attention-related N140 potential even in NC and DC and the lower SEP amplitude increase in SAC, observed in elderly subjects. These findings agree with recent hypotheses that suggest a decrease of the inhibitory control of the attention mechanisms during aging.