Using diffusion tensor imaging to identify the structural neural correlates of visuospatial and motor skill learning processes

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Project Summary/Abstract The simple act of testing for specific cognitive impairments prior to therapy may identify older adults who will receive little to no benefit from the motor rehabilitation regimen. Studies have shown that older adults tend to learn motor skills at a slower rate and to a lesser extent than younger adults. Given aging populations also experience cognitive decline, where one in five older adults (age>65) have some form of cognitive impairment, poorer motor learning capacity may, in part, be linked to the presence of cognitive impairments rather than to chronological age. We recently showed that visuospatial impairment, specifically, may disrupt an older adult’s ability to learn and retain new motor skills; in this previous study, we used a visuospatial test that evaluates only visual perception and visuo-constructional ability, whereas the visuospatial domain is much broader (e.g., visual memory and learning, spatial attention, etc.). The proposed research will extend our previous findings by evaluating which aspect of visuospatial function is most predictive of motor learning capacity, and by localizing the neural substrate that underlies this predictive relationship. Like motor learning capacity, measures of white matter within the brain decline with age but are still quite variable. Recent studies have shown that variance in white matter integrity between parietal and frontal cortices explains variance in several motor learning tasks. Since these structures and pathways are also involved in visuospatial functions, we hypothesize that visuospatial tests have predictive value because they probe the health of critical neural mechanisms of motor learning. One candidate white matter pathway may be the right superior longitudinal fasciculus (SLF), as it connects cortices implicated in visuomotor processes. However, recent studies investigating the relationship between visuospatial function and right SLF structural integrity report conflicting findings such that the predictive power of visuospatial testing on right SLF health remains unclear. Based on our pilot data, our central hypothesis is that visuospatial and motor learning processes are integrated in the right SLF in a manner such that visuospatial testing will predict motor skill retention. To test this hypothesis, we will expand on our previous findings by using a comprehensive testing battery that spans the breadth of the visuospatial domain, and track motor skill retention over a one-month period. We will use structural neuroimaging techniques to quantify SLF integrity and then evaluate its relationship with motor skill retention and visuospatial function. The results of this project will have multifaceted implications across multiple neuroscience fields: we will be able to advance neuroanatomical understanding of white matter’s role in motor learning and visuospatial integration, provide clinical practice with an evidence-based tool to predict who will (or will not) respond to motor rehabilitation, and potentially identify the right SLF as a neuroanatomical target for neurorehabilitation.