Two cell types turn taste into a decision

Researchers used mice performing a decision-making task based on taste mixtures. Using high-density electrodes, they recorded the activity of individual neurons in the gustatory cortex (the brain region that processes taste signals). The study, published in eLife, identifies two types of neurons: cells that encode taste linearly, and cells that encode taste categorically.

Linear cells measure the degree of a taste: exactly how sweet or bitter is this? Categorical cells register not the intensity, but the class: is this the taste that means I should go left or right? During taste sampling, linear cells are active. Just before a decision, categorical cells take over. That pattern proved consistent and reproducible across individual animals.

Which cells are actually necessary?

To test which cells are functionally essential, the researchers built a computational brain model (a recurrent neural network) mimicking the gustatory cortex. By suppressing specific cell groups in the model, they measured what changed in its decision-making behavior. Silencing linear or categorical neurons caused behavioral performance to collapse. Many other cell types could be suppressed with no measurable effect.

What this says about brain aging

This mechanism has broader relevance. As brains age, the precision of neural circuits declines. If specific cell types in the cortex are responsible for the transition from sensation to decision, loss of precisely those cells may contribute to cognitive decline. The researchers suggest their findings may reflect a general principle of cortical processing beyond the taste cortex alone. That interpretation requires further investigation.

For cognitive aging research, the open question is whether similar linear and categorical coding patterns exist in other brain regions, and whether they change with age. That remains unknown, but the study provides a methodological tool to investigate it.

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