Knowledge of semantic features in mild cognitive impairment

• People with MCI identified shared features of word pairs (e.g., tiger-zebra).
• Findings suggest greater impairment in lower-level semantic features in MCI.
• MCIs committed more errors in biological than artifact stimuli.
• Both process and content impairments play a role in semantic function in MCI.

Mild cognitive impairment (MCI) is defined as impairment in cognitive function in the absence of dementia, and in many cases it represents a prodromal state of dementia. Semantic function is impaired in MCI, but the exact nature of the impairment remains to be understood. The present study aimed to investigate the nature of this impairment using two semantic feature tasks. In the first, participants generated the most specific shared semantic feature for word pairs (e.g., how is a tiger like a zebra?) and in the second they selected the shared feature in a multiple choice format. Half of the stimuli were biological kinds, and half were artifacts. Participants were cognitively healthy older adults (n = 39) and people with MCI (n = 21). Overall, MCI participants committed more errors than control participants, with lower performance in biological items relative to artifacts. MCI participants also committed proportionally more superordinate errors than control participants, suggesting greater impairment in lower-level semantic features. MCI participants did not benefit from the multiple choice format, suggesting degradation of core semantic representations. In contrast, correlations were observed between performance on the experimental task and verbal fluency measures, but not semantic function, indicating selection and retrieval deficits in MCI. Thus, we hypothesize that both process and content impairments play a role in declines in semantic function in MCI.