AbstractBackgroundReliable markers of language decline in patients with amnesic mild cognitive impairment (aMCI) are critical for the early detection of Alzheimer’s disease. However, language impairments may be subtle and difficult to be detected from behavioral performance measures. N400 is an Event‐Related Potentials (ERP) component to index the semantic processing and has been used to reflect the deficit of language comprehension in aphasic patients (Chang et al., 2016). This study manipulated the predictability and plausibility of the Chinese classifier‐noun agreement to examine whether these two effects on N400 may serve as potential markers for the early detection of aMCI.MethodThis study recruited 16 MCI patients and 17 age‐matched healthy elders from the memory clinic of Cardinal Tian Hospital in Taiwan. All participants received [18F] florbetaben PET and a set of standardized cognitive tests, including Mini‐Mental State Examination (MMSE), verbal fluency, and Wechsler Memory Scale‐III (WMS‐III), for MCI diagnosis. The positivity rate of the aMCI group was 43.75%, and 31.25% for the healthy elder group. During the ERP recording, participants would read a series of classifier‐noun phrases, and each classifier was paired with a highly predictable, a low predictable, or an implausible noun.ResultWe performed the Linear mixed models to examine whether the predictability effect (high vs. low predictable nouns) and plausibility effect (high vs. implausible nouns) on N400 (300‐500ms) would be explained by the particpants’ cognitive performance. The data revealed that participants with higher scores of MMSE (b = ‐0.019, SE = 0.010, t = ‐1.969), verbal fluency (b = ‐0.023, SE = 0.008, t = ‐2.781), and WMS‐III (b = ‐0.002, SE = 0.001, t = ‐2.370) showed more pronounced predictability effects, which reflecting better semantic integration processing. Meanwhile, participants with poor memory engendered a reduced plausibility effect (b = ‐0.004, SE = 0.001, t = ‐3.972).ConclusionOur findings suggest that MCI patients would exhibit a deficit in semantic process. The predictability and plausibility effects on N400 may serve as ERPs markers to detect the language deficits in aMCI.