The Effect of Toxoplasma gondii on Acoustic Startle Response in an Inner City Population Open Access

Massa, Nicholas Marlin (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/n870zr01k?locale=en
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Abstract

Toxoplasma gondii (TOXO) infection affects approximately 1.1 million people in the United States annually. TOXO has recently been implicated in the etiology of psychiatric diseases, namely schizophrenia (Scz), and has been correlated with a decrease in cognition. The objective of this study is to assess the effect of TOXO on the acoustic startle response (ASR), a physiological measure of neural processing, accounting for sociodemographic and psychiatric factors. Physiological and psychological data along with biological specimens were collected from a primary care clinic at Grady Memorial Hospital serving the inner city of Atlanta, GA. From a cohort of 611 patients, those missing either demographic, biologic, or physiologic data were excluded leaving a final sample of 364 patients. A series of linear regression models were used to assess the impact of a TOXO seropositivity indicator, or TOXO serointensity, the amount of antibody produced by a subject, on ASR latency and amplitude controlling for demographics and psychiatric diagnoses. Both TOXO seropostivity and serointensity did not significantly associate with the latency of the acoustic startle response (F=0.23, p=0.6305; F=0.06, p=0.8014). However PTSD, and no other psychiatric covariates, did positively correlate ASR latency in seropositive individuals, but the correlation was attenuated when serointensity was taken into consideration (F=5.15, p=0.0238; F=3.51, p=0.062). ASR amplitude was significantly increased in TOXO seropositive subjects, and the effect was stronger using serointensity (F=7.41, p=.0068; F=10.05, p=0.0017). This significant increase in amplitude was measured when controlling for all other psychiatric covariates. An increase in amplitude has been attributed to a decrease in habituation to repeated stimuli, through dysregulation in both the hypothalamic-pituitary-adrenal axis, and through the amygdala. The increase in amplitude attributed to TOXO, potentially implicates these regions of the brain, and their respective neurotransmitters in TOXO's effects on the brain. In future studies we would hope to assess cytokines and other biomarkers to potentially discern a biological effect of TOXO that could contribute to the increased startle amplitude.

Table of Contents

BACKGROUND.………………………………………………………………………………1

METHODS.………………………………………………………………………………….....9

RESULTS……………………………………………………………………………………..12

DISSCUSION………………………………………………………………………………...16

REFERENCES………………………………………………………………………………..19

TABLES AND FIGURES……………………………………………………………………27

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