Midfrontal Theta and Cognitive Control During Interlimb Coordination Across the Adult Lifespan.

Interlimb coordination is required for adequate execution of most daily life activities. Yet, aging negatively affects interlimb coordination, impacting the quality of life in older people. Therefore, disentangling the underlying age-related neural mechanisms is of utmost importance. Here, we investigated neurophysiological processes of an interlimb reaction time task, including both simple and complex coordination modes. Midfrontal theta power, measured using electroencephalography (EEG), was analyzed as a marker for cognitive control. In total, 82 healthy adults participated, with 27 younger, 26 middle-aged, and 29 older adults. On a behavioral level, reaction time increased across the adult lifespan, and error rate was higher in older adults. Notably, aging disproportionately affected reaction times in the complex coordination modes, with larger reaction time increases from simple to complex movements than in younger adults, starting already at middle age. On the neurophysiological level, EEG showed that only younger adults had significantly increased levels of midfrontal theta power during complex relative to simple coordination modes, while no significant differences were found between simple and complex movements in middle-aged and older adults. The absence of this theta power upregulation with regard to movement complexity with increasing age might reflect a premature saturation of the available mental resources.