Relationships Between Striatal Gray Matter Integrity and Implicit Associative Learning
Corinna Y. Franco · eScholarship (California Digital Library) · 2019
Previous studies have implicated striatal structures (i.e., caudate, putamen) in implicit associative learning (IAL), or the learning of associations between events without conscious awareness that subserves language and habit learning.While previous neuroimaging studies have examined IAL in relation to striatal function and the integrity of white matter tracts emanating from the striatum, none have examined the relationship between striatal gray matter integrity and IAL.Gray matter integrity can provide valuable information about microstructural properties of caudate and putamen (e.g., degree of neuronal density) that may complement previous examinations of the neural substrates of implicit learning.In this study, 25 young adults (21.33 ± 2.20 years old) underwent diffusion tensor imaging and completed the Triplets Learning Task, which requires the acquisition of associations between two cues (location of red circles) with a target (location of green circle).Task performance (IAL scores) correlated with measures of bilateral caudate gray matter integrity (e.g., axial diffusivity [AD], mean diffusivity [MD], radial diffusivity [RD]).That is, better IAL scores were significantly related to lower bilateral caudate AD.Additionally, better IAL scores exhibited a marginally significant correlation with lower left putamen MD and RD and right putamen MD.These results for striatal gray matter integrity are consistent with previous neuroimaging studies demonstrating involvement of striatum in IAL.Moreover, they support the notion that gray matter integrity is sensitive to individual differences in cognition, even among healthy younger adults.