The relationship between motor imagery and corticospinal excitability: Is age a factor

This study examined motor imagery ability, working memory and corticospinal excitability in 15 young subjects (21 to 30 years) and 15 older subjects (55 to 80 years). To determine the effect of imagery on neural excitability focal transcranial magnetic stimulation (TMS) was applied over the primary motor cortex area while participants were at rest and while they imagined themselves performing a pincer grip or dorsiflexing the foot contralateral to the stimulated hemisphere. Motor evoked potentials (MEPs) were recorded from the contralateral first dorsal interosseous (FDI), abductor digiti minimi (ADM) and tibialis anterior (TA) muscles. Motor imagery abilities were comparable between young and older groups in terms of KVIQ scores (P >0.05) and congruence between imagined and executed movement durations (P >0.05). Older subjects had poorer visuospatial and kinesthetic working memory capacity than young subjects (P <0.05), while verbal working memory was the same. MEPs in the FDI muscle in particular were markedly increased when subjects imagined executing a pincer grip as compared to the rest condition (P <0.001). This was the case for both groups. Associations between imagery ability, working memory and imagery-induced increases in corticospinal excitability were generally weak. In combination these findings suggest that corticospinal excitability is enhanced when imagery tasks involve the target muscles in young and older subjects even when there is some compromise in working memory. (Abstract shortened by UMI.)...