A retino-collicular mechanism segregates visual from somatosensory circuits at perinatal life in mice

Mature cortical sensory areas are specialized to process unique sensory stimuli. Recent evidence shows that in the mouse embryo sensory cortices are prepared to respond to an incoming input from the periphery. However, whether these sensory circuits originate as modality specific modules, or they are segregated over time remains unknown. Here, we demonstrate that visual and somatosensory circuits originate as functionally intermingled modules, as whisker-pad stimulations at prenatal life led to a multimodal response activating both primary visual and somatosensory cortices. This multimodal response is switched to unimodal at birth via the superior colliculus, a midbrain structure where both modalities converge. Retinal afferent to the superior colliculus prompts the gating of visual from somatosensory circuits achieving sensory modality specificity at birth. Blocking stage I retinal waves resulted in prolonged convergence of somatosensory and visual circuits at the superior colliculus, which led to long-term consequences in the molecular identity of the superior colliculus and caused defects in eye-specific segregation and retinotopy. Hence, the superior colliculus stands as a key developmental regulator of sensory circuits by channeling modality stimuli to their appropriate sensory pathway. Overall design: Bulk RNA-seq of superficial and deep layers from superior colliculus at P6 after intraocular injections of 50 mM carbenoxolone (cbx, Merck, C4790) or saline into the vitreous humor of the eye at P0-P1. The bulk tissue were microdissected (three brains were pooled for each sample) and the total RNA was extracted as in previous publication (Moreno-Juan et al., 2017).