Hippocampal abnormalities in youth with alcohol-related neurodevelopmental disorder.

Individuals diagnosed with alcohol-related neurodevelopmental disorder (ARND) exhibit difficulty on hippocampally mediated memory tasks and show reduced hippocampal size. However inconsistencies exist regarding the affected memory functions and where within the hippocampi effects occur. Given recent studies showing anterior and posterior segments support distinct memory functions and sex dimorphisms in hippocampal function, we asked whether these factors influence memory performance in youth with ARND (n = 18) and typically developing controls (n = 17). Participants received a battery of memory tests and a structural MRI scan. Right and left hippocampi were manually traced; anterior and posterior segments were delineated at the uncus. Measured were intracranial volumes (ICV) and right and left hippocampi and hippocampal segments. Volumes were adjusted for ICV. Relative to controls, the ARND group had lower IQs and memory performance on most tasks and marginally smaller ICVs. Left and right hippocampal volumes and posterior segments were smaller in the ARND group. Although no sex differences were observed between groups, females overall had larger anterior hippocampi than males. Positive and negative associations between hippocampal and selective memory indices were found in the ARND group only. These findings are the first to suggest that posterior hippocampal development may be compromised in youth with ARND.