Mellott, J. G. | bioRxiv Science

bioRxiv2026

Delineating the posterior bank of the feline auditory cortex based on neurofilament proteins expressing SMI-32

The feline auditory cortex is understood to consist of 13 distinct subregions with unique anatomical and functional properties. Differential patterns of SMI-32 immunoreactivity are commonly used to identify the borders between these subregions; however, the detailed description of areal differences that is commonly cited did not include descriptions of the patterns observed along the posterior ectosylvian gyrus. Thus, the current manuscript aims to provide a more complete data set that can used to delineate the dorsal, intermediate, and ventral divisions of the posterior ectosylvian gyrus (auditory cortical regions dPE, iPE, and vPE, respectively) based on SMI-32 reactivity using the same methods and measures. Taken together, the current data and those published previously allow for a standardized approach to identifying all 13 auditory cortical subregions in this essential model of auditory cortical structure and function.

neuroscience↗

bioRxiv2025

Developmental and Stress-Induced Effects on 5-HT3R-Expressing Interneurons within Auditory Cortex

Early life stress (ELS) is a well-known predictor of neuropsychiatric disease and contributes to the development of sensory processing deficits that persist throughout life. Organisms are particularly susceptible to the deleterious effects of stress during critical periods, when neuroplasticity is heightened, and initial representations of the sensory environment are mapped to cortex. When ELS is induced during the auditory cortical (ACx) critical period, it impairs both neural and behavioral responses to a variety of auditory stimuli that rely on temporal processing. Mechanisms by which ELS may alter critical period plasticity are of particular interest in understanding ELS-related pathology, including the 5-HT3R interneuron system, which has been implicated in regulating neural activity during critical periods. Here we examined two principal subpopulations of interneurons in primary ACx: VIP and NDNF cells, which account for a majority of cortical neurons expressing 5-HT3R. The expression of the Htr3a gene during normal development and under ELS conditions was quantified using multiplex fluorescent in situ hybridization. We show that densities of cells expressing NDNF and VIP decrease following ear opening and across the ACx critical period, and that ELS results in the maintenance of elevated cell densities compared to age-matched controls. Further, Htr3a in VIP neurons is developmentally upregulated, and its expression is further increased by ELS beyond normal physiologic levels. Stress-induced shifts in these serotonergic interneurons may contribute to deficits that arise in auditory cortical and perceptual responses via effects on local cortical circuitry.

neuroscience↗