Prenatal tuning of thalamic spontaneous activity patterns regulates somatosensory map resolution

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. Traditionally, barrel size and definition are believed to be determined postnatally by whisker input and peripheral receptor density. However, prenatal thalamic spontaneous activity can influence somatosensory map development independently of whisker input. Thus, the mechanisms defining distinct barrel field territories, including size and definition, remain poorly understood. Here, we show that prenatal ablation of mystacial whiskers enhances the functional and anatomical definition of upper lip whisker barrels. These changes do not result from alterations in receptor density but rather stem from prenatal reconfigurations in the patterns of spontaneous activity within the thalamus. Our results unveil the role of prenatal synchronized thalamic activity in shaping cortical barrel size and functional map definition in the developing somatosensory system.