Defense Date


Document Type


Degree Name

Master of Science


Anatomy & Neurobiology

First Advisor

Dr. Marvin A. Meredith


When organisms learn and adapt to their environment or lose a sensory modality, neurons in the brain undergo a cellular process called ‘plasticity.’ This thesis explores the loss of a non- visual system (early deafness) and how it can affect visual plasticity. To examine this question, Golgi-stained cortical neurons were studied from the visual region PLLS from early-deaf cats and their hearing controls. Dendritic spine density and dendritic spine diameter are well-known indicators of synaptic plasticity and these neuronal features were measured using light microscopic techniques and Neurolucida. Within the visual PLLS, the mean spine density for the deaf cats was 1.171 ± 0.295 spines/micron, while for hearing cats it was 0.984 ± 0.227 spines/micron, which was a statistically significant increase (p<0.0001). The mean spine diameter for the deaf cats was 0.478 ± 0.119 microns, while for hearing cats it was 0.527 ± 0.211 microns, which is a statistically significant decrease (p<0.0001). These changes in dendritic spine properties indicate that the neurons in the PLLS underwent synaptic plasticity. These findings are significant because they show that visual regions of cortex can be affected by non- visual conditions or treatments such as early deafness.


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