Abstract:

OBJECTIVE:Aging is associated with a decline in cognitive and motor performances, which are a part of geriatric syndromes. Since aging is associated with morphological changes in the cerebellum and cerebellar morphology is a good predictor of cognitive and motor performances, so the study of cerebellar role in age-related decline in performance is necessary. Cerebellar transcranial direct current stimulation (ctDCS) has been proposed to study and facilitate the cerebellar function. However, lobule-specific dosing has not been investigated in healthy aging. This is important because the same electrode montage across different individuals for ctDCS (called the "one-size-fits-all" approach) can lead to inter-individual differences in the lobule-specific dosing of the electric field (EF). These differences can be due to the inter-individual variability and age-related changes in the cerebellar structure. To investigate such lobule-specific dosing differences in healthy aging, we modeled the lobular EF distribution across groups of 18 to 89 years for a commonly used "one-size-fits-all" ctDCS montage. MATERIALS AND METHODS:A fully automated open-source pipeline performed age-group specific computational modeling of EF using 18 age-appropriate human brain magnetic resonance imaging (MRI) templates. The 18 age-appropriate human brain MRI templates were obtained from a database found online at https://jerlab.sc.edu/projects/neurodevelopmental-mri-database/. We extracted the EF magnitude (called EF strength) across the 28 cerebellar lobules based on a spatially unbiased cerebellar atlas. We investigated the aging effects on various measures of specificity including the ratio of the mean lobular EF at the lobules beneath the active electrode (ipsilateral [right] lobules VIIIa, VIIIb, IX) divided by the mean EF across both the targeted (ipsi) and the contralateral (contra) cerebellar hemisphere. RESULTS:Two-way ANOVA showed that the lobules as well as the age group (and their interaction term) had a significant effect (p