How the olfactory bulb maintains stable odor manifolds amid adaptation and representational drift

Adaptive coding in sensory circuits enables stable perception while accommodating experience-dependent changes. In the olfactory bulb (OB), repeated odor exposure reshapes population activity even without explicit behavioral feedback, but the underlying circuit mechanisms remain unclear. By analyzing longitudinal two-photon calcium imaging datasets from the mouse OB, we identified three concurrent forms of representational change: gain adaptation, similarity-dependent pattern separation or convergence, and a rotation of encoding subspace resulting in the representational drift. Using a computational model of the mitral cell-granule cell circuit, we showed that Hebbian plasticity and structural connectivity constraints are sufficient to reproduce these transformations. Despite global representational drift, the relative geometry of odor response vectors remained stable, preserving a low-dimensional odor manifold. Together, our results reveal how local plasticity and network structure jointly enable both stability and flexibility in early sensory coding.