Disrupted sensory processing, characterized by over-or underresponsiveness to environmental stimuli, has been reported in children with a variety of developmental disabilities. This study examined the effects of prenatal stress and moderate-level prenatal alcohol exposure on tactile sensitivity and its relationship to striatal dopamine system function in thirty-eight 5-to 7-year-old rhesus monkeys. The monkeys were from four experimental conditions: (a) prenatal alcohol exposed, (b) prenatal stress, (c) prenatal alcohol exposed + prenatal stress, and (d) sucrose controls. Increased D 2 receptor binding in the striatum, evaluated using positron emission tomography neuroimaging, was related to increased withdrawal (aversion) responses to repetitive tactile stimuli and reduced habituation across trials. Moreover, prenatal stress significantly increased overall withdrawal responses to repetitive tactile stimulation compared to no prenatal stress.Sensory processing disorders, characterized by under-or overresponsiveness to sensory stimulation that most individuals perceive as harmless (Ayres & Robbins, 1979) NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript estimated to occur in 5% of the general population (Ahn, Miller, Milberger, & McIntosh, 2004) and seem to pose a unique challenge for people with developmental disabilities (Baranek, 2002), including autism, attention deficit hyperactivity disorder (ADHD), fragile X syndrome, and other developmental disabilities (Ayres & Tickle, 1980;Baranek, 1999;Baranek & Berkson, 1994;Baranek, Foster, & Berkson, 1997;Cermak & Daunhauer, 1997;Grandin, 1992;Kinnealey, 1973;Larson, 1982;Mangeot et al., 2001;Miller et al., 1999). Understanding the neurobiological processes associated with sensory processing disruptions is important to developing appropriate preventative and intervention approaches.This study examined whether disrupted sensory processing occurs in monkeys as a result of prenatal exposure to alcohol and/or stress, and if so, whether it would be associated with dopamine functioning in the striatum assessed with positron emission tomography (PET) neuroimaging. We employed a primate model for these studies because in human studies causal conclusions are difficult to reach due to confounding variables. Even with the best statistical analyses it is difficult, if not impossible, to separate completely the effects of variables associated with alcohol use, such as psychological stress, tobacco use, or chaotic home life, from the effects of fetal alcohol exposure per se. Nonhuman primates also have the advantage of gestation characteristics and early development similar to the human, and their shorter life span makes longitudinal studies somewhat easier to conduct. Rhesus monkeys were used because of the large amount of available data on their behavior and development in laboratory settings (Harlow & Harlow, 1969;Suomi, 1997) A. Jean Ayres (1964), an occupational therapist and educational psychologist, coined the term "tactile defensiveness" t...

These results suggest that the vulnerability of the DA system to the effects of moderate doses of alcohol during gestation depend on the timing of the alcohol exposure. Early-gestation moderate alcohol exposure resulted in a reduction or blunting of dopaminergic function in adulthood, whereas middle to late exposure (without early exposure) either induced the opposite pattern or heightened dopaminergic function. Continuously exposed monkeys showed the largest effect, suggesting that the sooner women stop drinking, the better it is for the fetus.

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