<p>Those with an autism spectrum diagnosis (ASD) have been found to process emotional faces differently than other populations. Processing of emotional faces requires engagement of temporal, frontal, occipital, and limbic brain regions. Functional activity has been shown to differ in those with an ASD, particularly in the amygdala, inferior frontal cortex (IFC), and temporal brain regions. However, the consistency and direction of these associations have been inconsistent across studies. Recent findings have demonstrated that measures of neuron density differ in those with an ASD. Some of these regional differences in cytoarchitecture coincide with regions important to emotional facial processing. Therefore, the interaction between cytoarchitecture and functional activity may be important in elucidating unique neurophysiology in ASD. The present study uses diffusion weighted imaging (DWI) and functional magnetic resonance imaging (fMRI) data from the Adolescent Brain Cognitive Development^sm (ABCD®) study to investigate the relationship between cytoarchitecture and functional activity during emotional face processing in those with an ASD. 149 individuals with a reported ASD and 10,146 individuals with no reported diagnosis of an ASD (nASD) were identified. The emotional n-back (EN-Back) task was administered during fMRI acquisition, activating regions of the brain associated with processing emotional faces. Neuron cell body density was positively correlated with functional activation in the left amygdala in the ASD group but not the nASD group. These findings suggest that a unique relationship may exist between neuron cell body density in the left amygdala and functional activity while processing emotional faces in those with an ASD.</p>