Preserved semantic categorical organization in mild cognitive impairment: a network analysis of verbal fluency

Abstract

The decline in semantic verbal fluency as we age may originate from both semantic memory degradation and executive function deficits. We investigated to what extent semantic memory is organized into categories in older adults with mild cognitive impairment (n=81) and healthy controls (n=83). We obtained the semantic networks automatically from the probability of co-occurrence of words in a verbal fluency test and characterized them with graph-theory tools. We found that the degree of categorical organization was similar for both diagnostic groups, but there was a higher tendency to transition to other categories during word production in the patient group. These results suggest that the semantic network is preserved in mild cognitive impairment, but also that the existing associations are exploited less efficiently during long-term memory search, possibly because of deficits in executive function.