非表示:
キーワード:
Aging; EEG; Language Comprehension; Working Memory
要旨:
Recent advances in electrophysiological methodology are currently transforming the neuropsychology of language, but have only been sparsely employed to study the decline of language comprehension across the age trajectory. I present results from two studies examining age differences in the neural substrates underlying successful sentence comprehension, using resting-state (RS) electroencephalography (EEG) and task-related EEG. Employing frequency analysis, beamforming, and functional connectivity analysis, we found decreased RS theta-band power in the left-hemispheric language network to predict comprehension success irrespective of age. On the contrary, alterations of RS theta in a decoupled, domain-general brain network predicted the age-related language comprehension decline. The results emphasize the importance of domain-general cognitive abilities for successful language comprehension in healthy adult aging. Task-related EEG showed lower oscillatory power within alpha band to predict sentence encoding in young adults. This was less pronounced in the middle-aged adults, turning into a power increase in older adults. This neural desynchronization-to-synchronization shift across the lifespan likely reflects a cognitive shift in encoding strategies: At young age, bottom-up encoding may dominate, achieved through cortical disinhibition—allowing enriched information routing throughout the language network. At old age, resource limitations may necessitate an increased reliance on top-down encoding, mirrored in cortical inhibition to avoid information overload. I suggest that declining language comprehension across the lifespan is characterized by changes to the underlying electrophysiological processing networks that are, in turn, associated with changes in the functional dynamics within these networks during task performance.
