Neuroscience and Neurobiology Commons^™

Microstructural Alterations In Grey And White Matter Following Early-Onset Deafness In The Cat, Alessandra Sacco

Electronic Thesis and Dissertation Repository

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, …

Multisensory Responses In Primary Auditory Cortex Of The Cat, Catherine Boucher

Electronic Thesis and Dissertation Repository

Core auditory cortex of the cat is comprised of primary auditory cortex (A1) and the anterior auditory field (AAF). Neurons in both fields respond strongly to acoustic stimuli and are tonotopically organized. In hearing animals, a small number of cells in AAF respond to tactile stimulation. However, it is unclear if multisensory input influences responses in A1. In this study, multisensory stimuli were developed by pairing a pure tone stimulus with a flash stimulus at various stimulus onset asynchronies. A linear multielectrode array recorded multi-unit activity in A1 across cortical layers. We identified unisensory auditory, unisensory visual, bimodal, and subthreshold …

Differential Thickening And Thinning Of Auditory Cortex In Deaf Cats Revealed With Ultra-High-Field Mri, Stephen G. Gordon

Electronic Thesis and Dissertation Repository

In the absence of hearing, the brain must adapt and repurpose the former auditory cortex. In this study we scanned normal hearing (n=29) and deaf (n=26) cats to identify cortical areas of differing thickness using the auditory regions from a 3D cortical atlas. Compared to hearing controls, differential thickening and thinning was observed in specific regions of the deaf auditory cortex. More dorsal auditory regions tended to be bilaterally thicker in the deaf group, while more ventral regions in the left hemisphere were thinner. The location and nature of these changes creates a gradient along the dorsoventral axis wherein dorsal …

Characterizing The Cortical Contributions To Working Memory-Guided Obstacle Locomotion, Carmen Wong

Electronic Thesis and Dissertation Repository

While walking in complex environments, the ability to acquire information about objects in our surroundings is essential for successful obstacle negotiation. Furthermore, the ease with which most animals can traverse cluttered terrain while grazing, exploring, or hunting is facilitated by the capacity to store obstacle information in working memory (WM). However, the underlying neural substrates supporting such complex behaviours are poorly understood. Therefore, the goal of this thesis is to examine the neural underpinnings of WM-guided obstacle negotiation in the walking cat.

Obstacle locomotion was studied in two main paradigms, characterized by whether obstacle presence was detected via vision or …

Hierarchical Organization In Auditory Cortex Of The Cat Using High-Field Functional Magnetic Resonance Imaging, Amee J. Hall

Electronic Thesis and Dissertation Repository

Sensory localization within cortex is a widely accepted and documented principle. Within cortices dedicated to specific sensory information there is further organization. For example, in visual cortices a more detailed functional division and hierarchical organization has been recorded in detail. This organization starts with areas dedicated to analysis of simple visual stimuli. Areas higher in the organization are specialized for processing of progressively more complex stimuli. A similar hierarchical organization has been proposed within auditory cortex and a wealth of evidence supports this hypothesis. In the cat, the initial processing of simple auditory stimuli, such as pure tones, has been …