Hierarchical sensory processing in zebrafish thalamocortical-like circuits

Thalamocortical projections shape the functional regionalization and parallel sensory computations across the mammalian cortex. However, the principles of thalamocortical computations in nonmammalian vertebrates remain underexplored. In this work, we investigated how the zebrafish pallium, a homolog of the vertebrate cortex, receives and processes sensory information and how its architecture compares to thalamocortical circuits in other vertebrates. We revealed that the preglomerular complex (PG), a thalamocortical-like pathway, is the primary source of visual and vibrational information to the zebrafish pallium. PG and its pallial projections exhibit sensory-specific and topographically organized responses. By contrast, pallial neurons display topographically organized hierarchies, ranging from sensory-specific to multimodal and coincidence-detecting nonlinear responses. Our results suggest that hierarchies of sensory transformations across topographically organized thalamocortical-like circuits reflect a convergent principle across vertebrates.