Master of Science
Lomber, Stephen G.
Following sensory deprivation such as deafness, compensatory plasticity underlies the reorganization of sensory-specific brain areas to process remaining intact modalities. Previous studies have explored microstructural consequences throughout the brain following auditory deprivation, including the effect of deafness on cerebral water diffusion. However, nearly all investigations have studied these neuronal changes in humans rather than animal models. The present study investigates microstructural differences between 19 hearing and 27 early-deaf cats via diffusion tensor imaging (DTI). Diffusivity scalars were compared within 155 grey and 21 white matter regions. Results indicate structural plasticity in various regions throughout the deaf brain in both tissues, including perirhinal cortex, frontalis agranularis, as well as corpus callosum, superior longitudinal fasciculus, and more. This is the first study to examine DTI alterations following auditory deprivation in cats perhaps due to compensatory plasticity, overall demonstrating that early-deafness incites alterations throughout the brain.
Summary for Lay Audience
As living organisms, we are constantly surrounded by a complex, changing environment. Our brains must process various stimuli quickly to allow us to respond and behave accordingly. However, as our environment changes, our brain must adapt and rewire communicative networks to optimize processing in a new environment. Therefore, cellular processes in the brain will adjust in response to changes in surroundings. For instance, following the loss of a sense such as hearing, neural networks will exhibit plasticity, or the ability to change in order to compensate for the loss of sense. This is a phenomenon known as compensatory plasticity, as this may lead to enhanced functioning or processing of remaining senses following hearing loss, such as superior visual skills which can be observed in deaf animal models. Considering the possibility of plasticity following auditory deprivation, what exact changes occur throughout the brain to permit these heightened abilities? Previous studies have examined cellular plastic consequences of hearing loss, including the impact deafness has on the movement of water molecules in the brain. However, nearly all investigations have studied these neuronal changes following deafness in humans rather than animal models. The cat is a well-studied model for auditory deprivation, however the impact deafness has on cerebral water diffusion is an uncharted concept in cats. The present study investigates microstructural differences using diffusion tensor imaging (DTI), a noninvasive magnetic resonance imaging method, specifically comparing structural changes within both tissue types in the brain, grey (GM) and white matter (WM), between 19 hearing and 27 cats that were deafened prior to any auditory experience. Different parameters concerning water diffusion known as diffusivity scalars were investigated in both deaf and hearing control groups within 155 GM and 21 WM regions. Results indicate structural plasticity in various grey and white matter regions throughout the deaf brain, which are not solely involved in processing sound. This is the first study to examine DTI plastic changes following hearing loss in cats perhaps due to compensatory plasticity, overall demonstrating that deafness early in a cat’s life incites alterations throughout the entirety of the brain.
Sacco, Alessandra, "Microstructural Alterations in Grey and White Matter Following Early-Onset Deafness in the Cat" (2020). Electronic Thesis and Dissertation Repository. 7301.
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Available for download on Tuesday, August 31, 2021