Date of Award

8-2011

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Advisor

Alan B. Cobo-Lewis

Second Committee Member

Shawn W. Ell

Third Committee Member

Thane E. Fremouw

Abstract

This dissertation presents research on some of the cognitive and perceptual concomitants of agenesis of the corpus callosum (AgCC), a congenital condition in which the corpus callosum, typically the primary neural pathway connecting the two hemispheres of the brain, fails to develop between the brain's hemispheres. It has been proposed that non-callosal interhemispheric pathways develop compensatory functions for individuals with AgCC. Broadly, the aim of the present research was to contribute to a greater understanding of the functional extent and limits of compensatory mechanisms for individuals with AgCC. The first study examined the ability of individuals with AgCC to identify and discriminate among basic facial expressions of emotion. Additionally, the relative durations of participants' gaze toward the eyes, nose, and mouth of pictures of emotionally expressive faces were examined to assess the role of visual selective attention in emotion discriminability for individuals with AgCC. The analyses revealed that participants with AgCC exhibited impairments in the identification and discrimination of facial expressions of emotion. Additionally, participants with AgCC demonstrated atypical patterns of gaze while viewing the faces. Analysis of the effect on emotion discriminability of participants' gaze to various facial features suggests that increased gaze toward the eyes and, more generally, increased gaze distributed within the T-shaped facial region comprising the eyes, nose, and mouth can yield improvements in emotion discriminability for individuals with AgCC. Overall, the results suggest that gaze atypicalities contribute to impairments in emotion discriminability for individuals with AgCC. The second study explored the perceptual grouping of visual elements during binocular rivalry, a perceptual phenomenon that occurs when each eye is presented with an image that differs from that presented to the other eye. By assessing perceptual grouping, inferences were made regarding the interhemispheric sharing of visual information for individuals with AgCC. The analysis revealed no significant grouping differences between control participants and participants with AgCC, suggesting that compensatory mechanisms facilitate interhemispheric sharing of visual information for individuals with AgCC. Additionally, the results suggest that these compensatory mechanisms can facilitate relatively long-term cooperation between the cerebral hemispheres during visual processing.

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