Bilateral Enucleation Before & After the Critical Period for the Specification of Interhemispheric Axonal Connectivity Induces Similar Changes on White Matter Fractional Anisotropy

Christopher D. Kroenke¹, Jaime F. Olavarria², Andrew S. Bock², Erin N. Taber¹, Byung Park¹

An animal model has been developed to investigate the relationship between axonal connectivity and water diffusion fractional anisotropy (FA) in white matter (WM). Binocular enucleation, a form of visual deprivation, prior to the critical period for the specification of interhemispheric axonal connectivity produces abnormal connectivity patterns in mature ferrets. Correspondingly, WM FA within early-enucleated ferrets is lower than normally-sighted control animals. Enucleation subsequent to the critical period results in normal connectivity patterns. However we, find abnormal WM FA within late-enucleated ferrets resembling that of early-enucleates. This suggests reduced WM FA arises from microstructural-level changes rather than abnormal to axonal connectivity.