Friend or Foe: The nose knows

A new brain-imaging study by researchers at the Montreal Neurological Institute (MNI) of McGill University reveals that humans have a far more sophisticated sense of smell than previously believed and are able to accurately smell the difference between a stranger and a friend. Participants in the study were asked to identify four different odors: their own, a stranger’s, a friend’s and a normal or common everyday odor; while in a positron emission tomography (PET) scanner. The study, published in the scientific journal Cerebral Cortex, found that body odors are processed by an entirely different nerve pathway in the brain than common odors. Interestingly, the researchers also discovered that a stranger’s body odor activates the same regions in the brain that are known to respond to fear or danger, namely the amygdala and insular cortex. “Our study demonstrates that the olfactory system has preferential processing for behaviorally important stimuli. This means that stimuli that are perceived as very important for us – either for our survival, finding food, or are carrying other important signals, such as mate selection signals - are processed faster and more accurately by specialized neuronal networks. It is known that the auditory and visual systems work in much the same way and we have now demonstrated this for the olfactory system.” says Dr. Johan Lundstrom, lead investigator and former post-doctoral fellow at the MNI, currently Assistant Member at the Monell Chemical Senses Center in Philadelphia. “This explains why participants perceived a stranger’s body odor as more intense, and less pleasant than the other odors. A stranger’s body odor is a behaviorally important stimulus because it is unfamiliar and might signal danger. Therefore, the brain has developed a mechanism to ensure that it grabs our attention.” “Body odor serves important functions from communicating social messages to distinguishing family members. Through evolutionary pressure, we have developed an entire separate network of nerves in the brain to process these important signals,” says Dr. Marilyn Jones-Gotman, neuroscientist at the MNI and co-author of the study. Sense of smell is proving important in other areas as well. The olfactory system is becoming increasingly significant as a clinical tool in the diagnosis of neurodegenerative diseases such as Parkinson’s. A number of studies have demonstrated that people with Parkinson’s and Alzheimer’s disease exhibit olfactory dysfunctions often several years before their clinical diagnosis. Therefore studies that contribute to a better understanding of how the brain processes odor may provide deeper insight into neurological diseases where olfactory deficits are seen. This research was funded by a grant from the Canadian Institutes of Health Research and the Swedish Research Council. About the MNI The Montreal Neurological Institute is a McGill University research and teaching institute, dedicated to the study of the nervous system and neurological diseases. Founded in 1934 by the renowned Dr. Wilder Penfield, the MNI is one of the world’s largest institutes of its kind. MNI researchers are world leaders in cellular and molecular neuroscience, brain imaging, cognitive neuroscience and the study and treatment of epilepsy, multiple sclerosis and neuromuscular disorders. The MNI, with its clinical partner, the Montreal Neurological Hospital (MNH), part of the McGill University Health Centre, continues to integrate research, patient care and training, and is recognized as one of the premier neuroscience centres in the world. At the MNI, we believe in investing in the faculty, staff and students who conduct outstanding research, provide advanced, compassionate care of patients and who pave the way for the next generation of medical advances. Highly talented, motivated people are the engine that drives research – the key to progress in medical care.