Date of Award

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Abstract

Eye movement deficits have been shown to be more prevalent in individuals diagnosed with schizophrenia compared to the general population. Dysfunction in the antisaccade (AS) system has been a topic of particular interest in this population, in part because it may provide insight into the pathophysiology of a complex, heterogeneous disorder. Researchers have broadened their investigation of AS deficits in an attempt to identify those who possess a genetic liability for a schizophrenia-spectrum disorder. These subthreshold traits, otherwise known as endophenotypes, are hypothesized to exist in individuals at-risk for developing schizophrenia (i.e., schizotypes), even though they may not display the overt symptoms associated with the disorder. The relationship between AS deficits and first-degree relatives of those with schizophrenia has been established in the literature, but only a handful of studies have investigated this relationship in psychometrically identified schizotypes. These deficits most notably include higher error rates and increased latencies in responding to visually presented stimuli. Impaired AS task performance may reflect underlying cognitive impairments associated with schizophrenia-spectrum disorders, especially in regard to mechanisms of working memory, attention, and executive function (mainly, inhibition). The current study investigated AS task performance in a sample of psychometric schizotypes, and the relationship between AS deficits and several measures of neuropsychological functioning. Data regarding the accuracy and latency of subject responses was recorded to determine if individuals in the target group displayed higher error rates and increased response latencies compared to controls. Eighty-eight undergraduates were assigned to either a psychometric schizotype (PS, n = 41) or matched comparison (MC, n = 47) group using the Wisconsin Schizotypy Scales (WSS) to determine group membership. Subjects completed several neuropsychological measures (e.g., Wisconsin Card Sorting Task), along with a custom, computer-administered AS task and infrared reflection technique for oculomotor measurements (ViewPoint EyeTracker, Arrington Research, Inc.,Scottsdale, AZ). Multivariate analyses incorporating mean latency, missed responses, and total correct responses between PS and MC groups were not significant, although univariate analyses produced significant differences between these groups for missed responses ( d = .46) and correct responses ( d = .44). Within-group analyses (i.e., positive v. negative schizotypy) also supported the hypothesis that positive schizotypes would display fewer correct responses and have increased latency rates ( F = 3.66, p = .019). Significantly more missed responses were also found in the positive schizotypy subgroup ( d = 1.27). Additional Pearson correlations found significant relationships between increased error rates and measures of working memory, particularly on those involving auditory and visual working memory. Findings from this study provide additional support for the likelihood of AS deficits serving as an endophenotype of schizophrenia. Psychometrically-identified schizotypes had significant difficulties with the AS task, while these deficits appeared more prominent in those endorsing positive symptoms of schizotypy. Moreover, these results support the broader hypothesis that AS deficits reflect cognitive impairments in inhibitory control commonly associated with the spectrum of disorders.

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