Deliberative Behaviors and Prefrontal-Hippocampal Coupling are Disrupted in a Rat Model of Fetal Alcohol Spectrum Disorders

Abstract

AbstractFetal alcohol spectrum disorders (FASDs) are characterized by a range of physical, cognitive, and behavioral impairments. Determining how temporally specific alcohol exposure (AE) affects neural circuits is crucial to understanding the FASD phenotype. Third trimester AE can be modeled in rats by administering alcohol during the first two postnatal weeks, which damages the medial prefrontal cortex (mPFC), thalamic nucleus reuniens, and hippocampus (HPC), structures whose functional interactions are required for working memory and executive function. Therefore, we hypothesized that AE during this period would impair working memory, disrupt choice behaviors, and alter mPFC-HPC oscillatory synchrony. To test this hypothesis, we recorded local field potentials from the mPFC and dorsal HPC as AE and sham intubated (SI) rats performed a spatial working memory task in adulthood and implemented algorithms to detect vicarious trial and errors (VTEs), behaviors associated with deliberative decision- making. We found that, compared to the SI group, the AE group performed fewer VTEs and demonstrated a disturbed relationship between VTEs and choice outcomes, while spatial working memory was unimpaired. This behavioral disruption was accompanied by alterations to mPFC and HPC oscillatory activity in the theta and beta bands, respectively, and a reduced prevalence of mPFC-HPC synchronous events. When trained on multiple behavioral variables, a machine learning algorithm could accurately predict whether rats were in the AE or SI group, thus characterizing a potential phenotype following third trimester AE. Together, these findings indicate that third trimester AE disrupts mPFC-HPC oscillatory interactions and choice behaviors.Significance statementFetal alcohol spectrum disorders (FASDs) occur at an alarmingly high rate worldwide. Prenatal alcohol exposure leads to significant perturbations in brain circuitry that are accompanied by cognitive deficits, including disrupted executive functioning and working memory. These deficits stem from structural changes within several key brain regions including the prefrontal cortex, thalamic nucleus reuniens, and hippocampus. To better understand the cognitive deficits observed in FASD patients, we employed a rodent model of alcohol exposure during the third trimester, a period when these regions are especially vulnerable to alcohol-induced damage. We show that alcohol exposure disrupts choice behaviors and prefrontal-hippocampal functional connectivity during a working memory task, identifying the prefrontal-hippocampal network as a potential therapeutic target in FASD treatment.