Dissertations, Theses, and Capstone Projects

Date of Degree

5-2015

Document Type

Dissertation

Degree Name

Ph.D.

Program

Psychology

Advisor

John J. Foxe

Subject Categories

Clinical Psychology

Keywords

EEG; endophenotype; schizophrenia; schizotypy; somatosensory processing; visual processing

Abstract

The experiments comprising this dissertation sought to contribute to the understanding of basic sensory processing in schizophrenia-spectrum disorders and risk-liability. We leveraged the sensitivity of visual processing deficits along with widely reported sensory-gating deficits (in other modalities) to develop a new paradigm assaying short-term visual adaptation to repetitive stimuli. In the first experiment, adaptation properties of the visual system were characterized in neurotypical adults using a classic "paired adaptation paradigm" and a more taxing "block adaptation paradigm," using high-density EEG. In the second experiment, we deployed our new visual adaptation assay in a clinical population. We replicated classic early VEP amplitude attenuation and uncovered novel visual adaptation deficits in participants diagnosed with a schizophrenia-spectrum disorder. We further tested the specificity of these findings by employing a somatosensory analog to the block adaptation paradigm utilizing vibrotactile stimulation of the median nerve. Differences in basic somatosensory function and adaptation were present in the clinical group although less apparent than in the visual system. In the third experiment, we examined whether altered visual adaptation could serve as a schizophrenia endophenotype. We utilized a shortened version of our visual adaptation paradigm (15mins, 32-channel electrode array) to characterize a larger sample of neurotypical adults who were also assessed using the Schizotypal Personality Questionnaire (SPQ). Multiple regression analysis revealed a significant relationship between high SPQ and less sensitive VEP adaptation. Overall the findings across these studies provide strong support for atypical visual adaptation in schizophrenia and suggest a potential role for altered visual adaptation as an electrophysiological schizophrenia endophenotype. Future studies employing pharmacological manipulations (e.g. administering nicotinic treatment or dopamine/glutamate/GABA agonists) and examining first degree relatives of patients may offer greater mechanistic insight into the processes underlying these observed phenomena.

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