Greater excitability and firing irregularity of tufted cells underlies distinct afferent‐evoked activity of olfactory bulb mitral and tufted cells

The two classes of principal neurons in the mammalian main olfactory bulb, mitral and tufted cells, respond with different firing latencies and rates to afferent‐evoked input; how these differences in activity arise is incompletely understood. Tufted cells receive stronger afferent‐evoked excitation than mitral cells, but this difference alone is insufficient to account for the greater afferent‐evoked firing in tufted versus mitral cells. Mitral and tufted cells exhibit significant intrinsic functional differences; compared to mitral cells, tufted cells fire action potentials with shorter durations and faster afterhyperpolarizations and exhibit twofold greater firing rate–current curve gains and peak rates. Tufted cells exhibit diverse firing modes, including tonic firing and irregular stuttering, and on average fire more irregularly than mitral cells. Collectively, stronger afferent excitation, greater intrinsic excitability and more irregular firing in tufted cells combine to drive distinct responses of mitral and tufted cells to sensory input.