Age-related Changes in Cortical Excitability Linked to Decreased Attentional and Inhibitory Control.

Understanding age-related changes in cortical excitability and their relation to cognitive functions will help to improve interventions based on non-invasive brain stimulation that aim to support cognitive function in older adults. Here, we investigate the relationship between cortical excitability, executive function, and underlying neural activity in samples of healthy young and older adults. These participants performed a Simon task during electroencephalogram (EEG) recording. During the task, participants had to respond to the colour of a lateralized stimulus while ignoring its spatial location. We studied event-related brain potential correlates of attentional and inhibitory control [i.e., the posterior contralateral negativity (N2pc) and central contralateral negativity (N2cc), respectively] related to the Simon task performance. We also used transcranial magnetic stimulation (TMS) EEG coregistration. In detail, we applied single-pulse TMS during EEG recording in order to analyse global mean field power (GMFP) and TMS-evoked potentials (TEPs) as correlates of cortical excitability. We found lower GMFP amplitude within 101-200 ms in older compared to young adults. Moreover, older adults showed smaller N45 amplitude and slower P180 latency. These findings suggest cortical excitability alterations related to ageing. Older adults also exhibited longer reaction times and N2pc and N2cc latencies, indicating that it took them longer to allocate attention to the target stimulus and inhibit the tendency to respond to the attended location. Finally, in older adults, cortical excitability alterations correlated with longer reaction times and N2pc latencies. These results suggest that age-related alterations in cortical excitability represent a dysfunctional change associated with physiological ageing.