How dogs smell

Dogs have more than 100 million sensory receptor sites in the nasal cavity.

(photo credit: Albert Arhó)

 Dogs spend much time smelling everything they encounter while walking because their noses are extremely sensitive and their brains have tremendous power to interpret what they inhale. 

With more than 100 million sensory receptor sites in the nasal cavity compared to only six million in people, the area of the canine brain devoted to analyzing odors is about 40 times larger than the comparable part of the human brain. In bloodhounds and some other dog breeds, their receptors range to nearly 300 million.

Now, researchers at Bar-Ilan University (BIU) in Ramat Gan have revealed amazing insights into dogs’ olfactory systems that are likely to pave the way for new applications in law enforcement, drug detection, medical diagnostics, and search-and-rescue operations.

They developed an optical sensor capable of remote sensing dogs’ brain activity in three key regions – the olfactory bulb, hippocampus, and amygdala – that play a critical role in how dogs differentiate among different smells.

In the study, scientists employed a cutting-edge detection structure system using laser technology and a high-resolution camera to capture brain activity in real time from four dog breeds. 

These dogs were exposed to four distinct scent stimuli – garlic, alcohol, menthol, and marijuana. The data were then analyzed using a machine-learning algorithm, revealing that the amygdala plays a significant role in scent differentiation, highlighting the emotional and memory-related aspects of odor processing.

It has just been published in the Journal of Biophotonics under the title “Sensing Dog Brain Reactions to Smell by AI Speckle Pattern Analysis.”

“We showed that the amygdala is crucial in the way dogs process and react to odors, with specific scents triggering distinct emotional and memory responses, and we are capable of optically detecting their brain activity in this region, said Prof. Zeev Zalevsky, from BIU’s Kofkin Faculty of Engineering. 

“This discovery could be the first step toward creating a device that enables us to better understand and interpret the unique way all dogs perceive and differentiate smells.”