Age-related changes in intracortical inhibition are mental-cognitive state-dependent

• We examined the effects of aging and of a cognitive task on ICI, ICF and CSP.
• ICI was significantly reduced in the oldest group, suggesting a deficit in GABAa.
• This difference disappeared in the task condition compared to the rest one.
• The mental state could modify the effect of aging on intracortical inhibition (ICI).

IntroductionThis study aimed to assess the impact of aging and ‘state-dependency’ on cortical excitability. Two studies investigated these factors using a motor task and found that the age-related differences observed at rest disappeared in the task condition. However, as both their tasks and excitability measurements involved the motor cortex, their results could be specific only to the motor system. To overcome this problem, the present study used a cognitive task to control mental state.MethodIntracortical inhibition/facilitation (ICI/ICF) were assessed in young and older adults at rest and during the cognitive task. The cortical silent period (CSP) was also evaluated.ResultsICI and CSP were reduced with aging. However, ICI differences between young and old people disappeared when they performed the cognitive task.ConclusionAge and mental state modify cortical excitability. Taking these factors into consideration is crucial to clinical research using cortical excitability as a possible biomarker of pathology.