For a long time, it was believed that genes primarily set the broad boundaries of the cortex, with areas specializing through postnatal, activity-dependent mechanisms. For the first time, we provide a combined approach to simultaneously examine both genetic and activity mechanisms during early development. Our findings reveal an early interplay between molecular signatures and activity patterns, occurring bidirectionally. On one hand, the differential expression of area-specific genes early on regulates cortical area identity by modulating ion channels and cell adhesion molecules, which, in turn, influence the activity properties of each area. On the other hand, early activity from brain regions such as the thalamus induces changes in gene expression that modify the genetic identity of cortical areas. Together, these results highlight a novel, earlier-than-previously thought interaction between genes and activity. This discovery promises to offer breakthrough insights into brain development, with potential applications for understanding both health and disease, particularly in neurodevelopmental disorders and sensory deprivation conditions.
Our results also emphasize the important, yet previously unknown, role of the superior colliculus (SC), an evolutionarily conserved structure traditionally linked to motor orientation and avoidance behaviors. We have shown that the SC plays a crucial role in the formation of cortical sensory pathways. This has sparked renewed interest in this well-studied structure and the need to reconsider its roles during development. In fact, a review we wrote on the emerging functions of the SC highlights that little is known about how its circuitry develops and evolves. Our study provides new insights into this structure, opening exciting new avenues for research across multiple fields of neuroscience.
