Electronic Thesis and Dissertation Repository

Thesis Format



Master of Science




Lomber, Stephen G.


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 multisensory multi-unit activity. We also found neurons where auditory-visual interactions either suppressed or enhanced neuronal activity. Additionally, visual stimulation can modulate the neural response to auditory inputs depending on the stimulus onset asynchrony. Taken together, the majority of neural activity in A1 in the cat is influenced by visual inputs.

Summary for Lay Audience

We know our brains process information from our eyes and ears, however little is known about how the brain processes and combines these two senses. Integration is known to occur, as seeing lip movements influences the speech sounds we hear. In this thesis, we investigated how the auditory part of the brain can be affected by vision. We will be examining the electrical activity of individual neurons in an animal model to determine if changes in activity affect auditory processing. We hypothesize that neurons in the auditory part of the brain are mainly activated by sound, but vision can modulate this activation. By comparing the sensory differences of neurons, we will be able to examine how the integration of sound and vision occurs in the brain. Understanding this sensory integration will better our ability to understand auditory processing in the brain, and changes in the brain following hearing loss.