Developmental trajectories of somatostatin-positive interneurons in the human auditory cortex from migration to maturation

We are interested in understanding morphological changes during development in the human auditory cortex and decided to focus on the development and maturation of inhibitory interneurons, particularly somatostatin (SOM+) interneurons that shape cortical circuits and regulate plasticity, which remains underexplored. The present study examines the development of SOM+ interneurons in the post-mortem human auditory cortex from the prenatal period to adulthood, within primary and association auditory cortices. We find that there is an increase in SOM+ interneurons in the infragranular and subsequently supragranular cortical layers between prenatal development and childhood. Soma size and aspect ratio increase between the prenatal development and adulthood, of varying magnitudes across subtypes and cortical layers. Neurite complexity is highest during fetal and early postnatal stages and decreases during adolescence. The density of SOM+ interneurons peaks in layers 2 and 3 during childhood and adolescence and decreases in adulthood, coinciding with known periods of auditory plasticity. Our findings provide critical insights into the structural and spatial changes in SOM+ interneurons that likely regulate the sensitive period of the human auditory cortex. Since alterations in SOM+ interneuron density are linked to various neurodevelopmental disorders, our results provide an important baseline for future functional and clinical investigations.