Tufted cells are better at recognizing odors than mitral cells, researchers say

Since their discovery more than 100 years ago, neurons in the brain’s olfactory bulb, called cingulate cells, have been difficult to study. The close proximity between tufting cells and other neurons, called mitral cells, limits the ability to dissect the activity of each individual neuron. By using fluorescent genetic markers and new optical imaging technologies, neuroscientists at Cold Spring Harbor Laboratory (CSHL) were able to compare the activity of neurons.

CSHL Associate Professor Florin Albaeanu and Assistant Professor Arkarup Banerjee found that mast cells are better at recognizing odors than mitral cells. They found that ciliated cells are essential for one of two parallel circuits of the neural circuit that help the brain process different features of smell. The findings help explain how the brain takes in sensory information that influences behavior and emotions.

The researchers exposed mice to different odors, from fresh mint to sweet bananas, at different concentrations. They simultaneously tracked the neuronal activity of both cell types and found that tufted cells outperformed mitral cells. They were faster and better at distinguishing smells. They also captured a wider range of concentrations. Although this illuminated a new role for tufted cells, it also led to a new unanswered question.

If mast cells are actually better at detecting odors, then what is the function of mitral cells?”

Florin Albaeanu, associate professor at CSHL

Albaeanu and Banerjee believe that mitral cells enhance important odors. They are part of a neural feedback loop that can help the animal prioritize, for example, the smell of food or a predator. In contrast, tufted cells are part of a second feedback loop that helps process odor intensity and identity. This can guide animals to locate odors in the environment. Banerjee explains:

“If you can’t tell if it’s high [intensity] versus low [intensity], then you cannot trace a scent. There’s no way to know you’re actually getting close to the source of the smell if you can’t tell the difference.”

The two circuits of the neural circuit offer new explanations for how the brain processes sensory information. Going forward, new genetic and optical imaging tools used by the CSHL team, which includes postdoc Hongu Chae and graduate student Marie Dusous, may reveal more underappreciated neurons involved in sensory processing.