Utility of Fox and Reverse Fox Finger Imitation Tasks for Screening Cognitive Impairment in Older Adults: A Neuroimaging Study

INTRODUCTION: This study aimed to evaluate the usefulness of the fox finger and reverse fox finger imitation tasks as screening tools for detecting cognitive impairment, including mild cognitive impairment (MCI) and dementia. METHODS: A total of 132 older adults visiting a memory clinic were classified into four groups: cognitively normal (CN; n=16), MCI (n=43), Alzheimer's dementia (n=60), and non-Alzheimer's dementia (n=13). Participants completed both imitation tasks, and performance was compared across groups. Sensitivity and specificity were calculated, and voxel-based morphometry (VBM) was used to identify brain atrophy associated with task performance. RESULTS: The fox finger task was successfully completed by 77.5% of participants, with significantly higher success in the CN group. The reverse fox finger task was more challenging, completed by only 21.7%. The sensitivity of the reverse fox finger task for detecting dementia and MCI was 88.5% and 79.1%, respectively, whereas the fox finger task showed lower sensitivity (36.1% and 13.9%, respectively) but higher specificity (100% vs 62.5%). Fox finger failure was associated with atrophy in the bilateral inferior frontal gyri and left frontal pole. Reverse fox finger failure was linked to more widespread atrophy, including the left angular gyrus, right hippocampus, and right posterior cingulate gyrus. Binary logistic regression confirmed that reduced gray matter volume in these regions significantly predicted task failure (p<0.05). CONCLUSION: The reverse fox finger task offers high sensitivity for detecting early cognitive decline, while the fox finger task provides high specificity, supporting their clinical use as rapid, non-invasive screening tools.