Parallel Mitral and Tufted Cell Pathways Route Distinct Odor Information to Different Targets in the Olfactory Cortex

TLDR

Odor signals are conveyed from the olfactory bulb to the olfactory cortex by mitral cells (MCs) and tufted cells (TCs). The study aims to determine how MCs and TCs differ in function and axonal connectivity. The authors compared odor responses and axonal projections of single, electrophysiologically identified MCs and TCs in mice. TCs exhibit faster, concentration‑independent responses and project densely to focal anterior olfactory cortex subareas, whereas MCs respond only to strong odors and project diffusely across the cortex, indicating temporally distinct odor information is routed to different cortical targets.

Abstract

Odor signals are conveyed from the olfactory bulb to the olfactory cortex (OC) by mitral cells (MCs) and tufted cells (TCs). However, whether and how the two types of projection neuron differ in function and axonal connectivity is still poorly understood. Odor responses and axonal projection patterns were compared between MCs and TCs in mice by visualizing axons of electrophysiologically identified single neurons. TCs demonstrated shorter onset latency for reliable responses than MCs. The shorter latency response of TCs was maintained in a wide range of odor concentrations, whereas MCs responded only to strong signals. Furthermore, individual TCs projected densely to focal targets only in anterior areas of the OC, whereas individual MCs dispersedly projected to all OC areas. Surprisingly, in anterior OC areas, the two cell types projected to segregated subareas. These results suggest that MCs and TCs transmit temporally distinct odor information to different OC targets.