Titolo della tesi: Characterization of Retina Signal Transformation in the Mouse Superior Colliculus
Neural circuits transform retinal input into behaviourally relevant visual representations, yet the computations linking these stages remain poorly understood. Here, we used dual-color in vivo two-photon calcium imaging in awake mice to simultaneously record presynaptic retinal ganglion cell boutons and postsynaptic neurons in the superior colliculus. This approach revealed that the superior colliculus applies distinct, feature-specific strategies to organize and process its inputs. Direction-selective and orientation-selective signals arrive as largely independent retinal streams with fundamentally different spatial architectures: direction selective inputs form very localized clusters, whereas orientation selective inputs are arranged in a broad, tiled map. Postsynaptically, the superior colliculus preserves the orientation selective organization but actively computes the direction selective map de novo, consistent with feature-specific local computation. Across stimulus conditions, the circuit exhibited flexibility: low spatial frequencies favored direction selective dominance, while high spatial frequencies enhanced orientation selective responses. This dynamic reweighting may represent an adaptive filtering mechanism that allows the retinocollicular pathway to shift between global motion analysis and local form processing depending on visual context. Together, these findings suggest that the superior colliculus functions not as a passive relay but as an active, feature-dependent integrator that stabilizes and transforms retinal representations to support adaptive visually guided behaviour.