Date of Award


Degree Type


Degree Name

Master of Science




Dr. Stephen Lomber

Second Advisor

Dr. Brian Timney

Third Advisor

Dr. Nagalingam Rajakumar


The purpose of the present study was to identify projections from auditory to visual cortex and their organization. Retrograde tracer wheat germ agglutinin conjugated to horseradish peroxidase was used to identify the sources of auditory cortical projections to primary visual cortex (areas 17&18) in adult cats. Two groups of animals were studied. In the first group, large deposits were centered on the lower visual field representation of the vertical meridian located along the area 17&18 border. Following tissue processing, characteristic patterns of cell body labeling were identified in extrastriate visual cortex and the visual thalamus. In auditory cortex, of the four tonotopically-organized regions, neuronal labeling was identified in the supragranular layers of the posterior auditory field (PAF). Little to no labeling was evident in the primary auditory cortex (AI), the anterior auditory field (AAF), the ventral posterior auditory field (VPAF) or in the remaining six non-tonotopicaly organized regions of auditory cortex. In the second group, small deposits were made into the central or peripheral visual field representations of primary visual cortex. Labeled cells were identified in PAF following deposits into regions of primary visual cortex representing peripheral, but not central, visual field representations. Furthermore, a coarse topography was identified in PAF, with neurons projecting to the upper field representation being located in the gyral portion of PAF and neurons projecting to the lower field representation located in the sulcal portion of PAF. Therefore, direct projections can be identified from PAF to primary visual cortex.



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