Learning and self-regulation of slow cortical potentials in older adults

Two groups of subjects, aged 20-28 and 50-64, respectively, matched for health status and verbal abilities, learned to control their slow cortical potentials (SCP) in a feedback paradigm by producing, on command, SCP shifts in either positive or negative direction. Both groups were able to differentiate significantly between the positivity task and the negativity task, with the differentiation score being only slightly (and not significantly) lower in older than in younger subjects. In all conditions, however, significantly more negative brain responses were obtained in older than in younger subjects. This effect was larger in the positivity task versus negativity task, and larger in trials without continuous SCP feedback versus trials with feedback. Additionally four learning tasks were carried out with all subjects. The older group demonstrated substantial performance deficits in two tasks with explicit learning (verbal and visual). In contrast, implicit learning (perceptual learning and skill acquisition) was not impaired with age. The results are at odds with the idea of general age-related learning deficit and concur with the hypothesis that only explicit, but not implicit, learning processes are compromised in older subjects. The pattern of consistently more negative SCP shifts produced by elderly subjects may indicate their impaired cortical inhibition. Another interpretation, which does not exclude the inhibitory deficit hypothesis but seems to better agree with other psychophysiological data, may be that older subjects have disturbance in the system controlling arousal and effort.