Sandeep Robert Datta is a Professor of Neurobiology at Harvard Medical School and a leader in the field of olfactory research. His life’s work has been exploring the biology of the olfactory system. We have come to understand that ‘smelling’ happens in the brain, not the nose, but how does the brain interpret odour? And what role does smell play in our mental wellbeing? When Chrissi met Bob at Harvard University, their conversation touched on the links between smell, emotion and memory.

Bob started with an explanation of the basic connections. Olfactory epithelium is the membrane of cells, including olfactory sensory neurons (OSNs), situated at the top of the nose to receive odours. The neurons send signals to the olfactory bulb in the brain, which then broadcasts to a variety of brain regions, including the amygdala (emotion and feeling). At the same time, the olfactory bulb has direct interaction with the hippocampus (memory). The brain is set up to link smell, emotions and memory. Without smell, the function of emotions and memory are negatively affected.

For Bob, this has roots in evolution. Smell evolved before sight and hearing, detecting chemistry in the world around us and developing emotional and behavioural responses to those signals. This is still intact in humans today. The intimate and direct connection to the limbic areas in the brain is critical to maintain emotional and mental health. Therefore, when the ability to detect smell changes, it’s reasonable to worry about the psychiatric impact of smell loss. 

Chrissi observes that when emotion and memory are negatively impacted, there is a consequential reduction in quality of life. Patients are looking for biomedical responses but the problem is really anxiety, depression and adjusting to the condition. On this basis, we need to reframe the questions to consider smell disorders within the realm of mental health, rather than simply as an ENT problem.

However, it’s not always the case that quality of life is negatively affected by smell disorders.  We know that some people live with little or no sense of smell and are content with their situation, whereas others will experience intense anxiety. And why will some individuals lose their sense of smell, while others experience the same illness and come through fine?

Bob suggests the evidence is beginning to point toward the unique genetic set-up carried by each individual that predisposes us to different responses to disease. Some genes sit quietly for a lifetime, only triggered under certain circumstances. For example, research has identified expression of a single gene that is linked to an increased risk of losing smell. This gene is expressed in the sustentacular cells, which may make them more susceptible to attack.

Emotional connections

Many people in the AbScent community talk about a distancing in their relationships and in relating to their partners. Chrissi queried whether this was a response to being unable to communicate through smell. The role of how we respond to smell in human relationships is still being explored but Bob suggested that a fracture in relationships might also be influenced by two other factors.  

Firstly, smell as a sense is difficult to describe. We lack an effective language to describe smell. This makes it difficult to describe the experience, which creates distance. And secondly, although there is debate about the role of smell in human social relationships, evidence is in favour of some sort of social communication using smell. When people lose this, they lose their experience of relationships and can experience changes in behaviour as the brain adjusts to new ways to navigate the world.

A final word

Bob advises that anyone feeling out of place, disjointed, or blue should seek help from their doctor. In his view, it’s not unusual or overreacting, this is an expected consequence of what’s happened to you and you should take care of yourself. Doctors may not always know about olfactory disorders, but they can help with psychological problems, so let them know how you’re feeling.

You can listen to the entire conversation on our podcast here.

Read Bob Datta’s insight into how Covid-19 induces smell loss and why some people take so long to recover.

Read our blog on Bob Datta’s explanation of brain elasticity and smell training.

June 07, 2022