Clinical Manifestations

Area of Science:

• Neuropsychology
• Cognitive Neuroscience
• Gerontology

Background:

• Mild cognitive impairment and Alzheimer's dementia (MCI/AD) affect cognitive functions, including language and executive functions.
• Category Fluency (CF) performance is a sensitive measure for assessing semantic memory and executive control.
• Clustering and switching abilities during CF are key indicators of semantic processing efficiency.

Purpose of the Study:

• To perform a meta-analysis characterizing clustering and switching abilities in adults with MCI/AD during CF tasks.
• To compare the performance of individuals with MCI/AD to cognitively healthy controls.
• To identify potential moderators influencing CF performance in MCI/AD.

Main Methods:

• A comprehensive bibliographical search was conducted across multiple scientific databases.
• Meta-analysis models were employed to analyze data from 29 selected studies, comparing MCI/AD individuals (n=1,778) with controls (n=3,632).
• Mean cluster size (MCS) and number of switches (NOS) were extracted as primary outcomes, with age, education, and Mini Mental State Examination (MMSE) scores as moderators.

Main Results:

• Individuals with MCI/AD demonstrated significantly smaller mean cluster sizes (G=0.30, p<0.001) compared to controls.
• The MCI/AD group exhibited significantly fewer switches (G=0.85, p<0.001) during CF tasks.
• Standard CF counts and MMSE scores were significant negative predictors of effect size, indicating poorer performance with lower scores.

Conclusions:

• Category Fluency (CF) mean cluster size (MCS) and number of switches (NOS) are significantly reduced in individuals with MCI/AD.
• These findings highlight deficits in both automatic semantic processing (clustering) and controlled executive functions (switching) in MCI/AD.
• Quantifying MCS and NOS can aid in assessing semantic processing deficits in clinical settings for individuals with MCI/AD.