Image of the Day: Smell Circuits

The brain wiring behind scent processing seems to scale across mammalian species.

Nicoletta Lanese
Jul 24, 2019
ABOVE: A section sliced from a mouse piriform cortex, a key region for smell processing composed of distinct layers. (Scale bar is 0.5 mm.)

Brain circuits underlying mammals’ keen sense of smell seem to be conserved across many animals, from mice to guinea pigs to opossums. Receptors in the nose shoot signals to a cluster of neurons in the brain—the olfactory bulb—and then on to the layered piriform cortex. The relative number of neurons involved in each successive stage is consistent across species, researchers reported July 18 in Current Biology

“So, if you told me the number of neurons in the nose, I could predict the number in the piriform cortex or the bulb,” says coauthor Shyam Srinivasan, a neuroscientist at the University of California, San Diego, in an announcement

S. Srinivasan, C.F. Stevens, “Scaling principles of distributed circuits,” doi:10.1016/j.cub.2019.06.046, Curr Biol2019. 

Nicoletta Lanese is an intern at The Scientist. Email her at