Semantic Relations in a Categorical Verbal Fluency Test: An Exploratory Investigation in Mild Cognitive Impairment

Abstract

Categorical verbal fluency tests (CFT) are commonly used to assess the integrity of semantic memory in individuals with brain damage. Persons with Dementia of the Alzheimer's Type display a reduced output on CFT, and a similar pattern has been reported in persons with amnesic Mild Cognitive Impairment (aMCI). The aims of the present study were to assess whether the semantic relations between lexical entries produced on a categorical fluency test were different between healthy persons and those with aMCI, and whether this difference was more pronounced in individuals who converted to dementia during a 3-year follow-up period. Methods: We recruited 34 individuals with aMCI and 29 matched healthy persons. During the follow-up period, 10 individuals converted to Dementia (aMCI-conv). Two measures assessing semantic relations between consecutively produced word pairs (Path length and Extended Gloss Overlap) were obtained from the Wordnet database. Results: The number of word pairs analyzed among the healthy participants (HP) and persons with aMCI were 498 (birds: 262; pieces of furniture: 236) and 395 (birds: 174; pieces of furniture: 221), respectively. Path length was lower in aMCI-conv than in HP (p = 0.035), but no differences were found between stable aMCI and HP, and between aMCI-stable and aMCI-conv. The ANOVA for lexical entries belonging to the "birds" category showed a significant effect of group (F = 5.630; p = 0.004); the post hoc analysis showed a significant difference between HP and aMCI-conv (p = 0.003). The "pieces of furniture" category was significantly affected by group (F = 4.107; p = 0.017); the post hoc test showed significant differences between aMCI-conv and healthy individuals (p = 0.049), and between aMCI-conv and stable aMCI (p = 0.001). Discussion: Individuals with aMCI who convert to dementia show a deterioration in the semantic relations between lexical entries, produced on a CFT. This phenomenon may be interpreted as a marker of a very early disruption of semantic memory.

Role of Executive Functions in the Conversion from Mild Cognitive Impairment to Dementia

“…Moreover, we showed that switching and categories verbal fluency are the executive function components that better predict MCI to dementia conversion in the ACS a year later ( Table 10). These findings are consistent with those from other authors [50][51][52][53][54][55][56][57] who supported that category generation should be included in cognitive composites to predict cognitive decline. However, a failure in category verbal fluency may be indicative of language impairment [55].…”

Semantic Priming in Mild Cognitive Impairment and Healthy Subjects: Effect of Different Time of Presentation of Word-Pairs

“…A possible explanation is that the progressive reduction of the knowledge of the attributes of objects and the relations between similar entities can cause the loss of SP effect that is the counterpart of difficulties observed in the semantic fluency tasks. In general, our findings could be accounted by spread-activation models, or proximity class of diffuse network models, in accordance to previous evidence from studies on semantic fluency [ 31 , 36 ]. On the other hand, learning models are not supported by our findings, since we observed a loss of SP over a long SOA in HS [ 34 ].…”

“…These results were interpreted in term of a progressive disruption of semantic system organization, leading the patients to retrieve more typical items of specific categories in respect to less prototypical elements. Our groups also reported that MCI individuals who will eventually progress to dementia produce words that are less related than the ones produced by healthy controls and stable MCI in a category fluency test [ 31 ]. This evidence can be interpreted as an effect of reduced strength of conceptual links between items belonging to a given category.…”

“…The models of SP are embedded in general conceptualizations of semantic memory based on observations obtained from other typologies of investigations. In Alzheimer’s disease and MCI, previous studies suggest that spread-activation models or more complex proximity models could be satisfactory to explain the disruption of lexical-semantic system [ 31 , 36 ].…”

What Drives Task Performance During Animal Fluency in People With Alzheimer’s Disease?

“…In a similar study, Taler et al (2019) found that healthy older adults produced words of denser semantic neighborhood and higher frequency than healthy younger adults. Quaranta et al (2019) stressed the relevance of semantic pairwise similarity, particularly in identifying people with MCI who convert to dementia from healthy individuals. In the present study, a measure of semantic association called Latent Semantic Analysis (LSA) was used ( Günther et al, 2015 ).…”