Thalamic spontaneous activity coordinates the timing of corticothalamic innervation in the visual system

Sensory processing relies on the correct development of circuits connecting thalamus and cortex. Visual corticothalamic axons (CTAs) invade the thalamic dorsolateral geniculate nucleus (dLGN) of the thalamus following an early postnatal time-regulated programme in mice. Retinal spontaneous activity influences the thalamic incursion of CTAs, however, the perinatal thalamus also generates intrinsic patterns of spontaneous activity whose role in modulating afferent connectivity remains unknown. Here, we found that patterned spontaneous activity in the dLGN is critical for the proper spatial and temporal innervation of CTAs. When the spontaneous dLGN activity is disrupted in vivo , CTA innervation is severely delayed until eye-opening. Indeed, visual input influenced the temporal development of CTAs by modulating thalamic activity, as embryonic enucleation enhanced thalamic calcium waves and accelerated the entrance of CTAs into the dLGN. Our results show that patterned spontaneous activity in the perinatal thalamus is a key element driving the wiring of visual circuits.