Detecting impaired language processing in MCI patients using around-the-ear cEEgrid electrodes

Mild cognitive impairment (MCI) is the term used to identify those individuals with subjective and objective cognitive decline but with preserved activities of daily living and an absence of dementia. While MCI can impact functioning in different cognitive domains, most notably episodic memory, relatively little is known about the comprehension of language in MCI. In this study we used around-the-ear electrodes (cEEGrids) to identify impairments during language comprehension in MCI patients. In a group of 23 MCI patients and 23 age-matched controls, language comprehension was tested in a two-word phrase paradigm. We examined the oscillatory changes following word onset as a function of lexical retrieval (e.g. swrfeq versus swift) and semantic binding (e.g. horse preceded by swift versus preceded by swrfeq). Electrophysiological signatures (as measured by the cEEGrids) were significantly different between MCI patients and controls. In controls lexical retrieval was associated with a rebound in the alpha/beta range and semantic binding was associated with a post-word alpha/beta suppression. In contrast, both the lexical retrieval and semantic binding signatures were absent in the MCI group. The signatures observed using cEEGrids in controls were comparable to those signatures obtained with a full-cap EEG set-up. Importantly, our findings suggest that MCI patients have impaired electrophysiological signatures for comprehending single-words and multi-word phrases. Moreover, cEEGrids set-ups provide a non-invasive and sensitive clinical tool for detecting early impairments in language comprehension in MCI.