A prenatal window for enhancing spatial resolution of cortical barrel maps

Abstract

Precise mapping of peripheral inputs onto cortical areas is required for appropriate sensory processing. In the mouse primary somatosensory cortex, mystacial whiskers are represented in large barrels, while upper lip whiskers are in smaller, less defined barrels. Barrel size and definition of these two functionally distinct barrel maps are believed to be determined by the type of whisker input and peripheral receptor density. However, spontaneous activity and transcriptional programs at prenatal developmental stages can influence somatosensory map development independently of sensory experience. Thus, the mechanisms defining distinct barrel field territories, including their size and definition, remain poorly understood. Here, we show that prenatal ablation of mystacial whiskers remap somatosensory cortical territories resulting in enhancement of the functional and anatomical definition of upper lip whisker barrels. These changes do not result from alterations in receptor type but rather stem from thalamic upper lip input-receiving neurons adopting a mystacial-like transcriptional profile. Our results unveil a regulated prenatal mechanism within the thalamus that maps available somatosensory input to ensure sufficient cortical barrel size and functional spatial resolution for sensory processing, irrespective of peripheral receptor type and density.