Molecularly defined olfactory bulb output neurons exhibit selective yet overlapping projections

M1, M2, T1, and ET2 olfactory bulb output neuron subtypes form anatomically and physiologically distinct channels, routing to overlapping yet selective cortical targets.

• Why it matters: Molecular profiling has defined finer olfactory bulb output classes, but how their morphology, projection patterns, and downstream convergence relate remained unclear.
• What they did: Using intersectional genetic targeting with two Cre lines, retrograde projection mapping from six cortical targets, and RiboTag-based sequencing, the study compared marker expression, morphology, and downstream targets across subtypes.
• The result: Retrograde labeling from the same cortical area recruited morphologically different OB neurons depending on the Cre driver; M1 was densely labeled from the cortical amygdala, M2 projected widely but could be selectively recruited from posterior piriform cortex, and electrophysiology showed intrinsic/functional differences.