A strong reaction to certain odors can help doctors determine the best treatment for patients in a coma or in a state of minimal consciousness, collectively known as a disorder of consciousness (DoC).
However, determining which condition a patient is suffering from can be difficult.
Sounds or images have been used to test DoC, and a new study shows that smells can help too. With proper refinement of this study, these conditions can be recognized by carefully selected scents placed under the patient’s nose.
The researchers wrote in their published paper: “Olfactory responses should be considered as markers of consciousness. Olfactory responses may aid in assessing consciousness and may contribute to therapeutic orientation.”
A team from the Southern Medical University in China conducted tests on 28 patients with different levels of consciousness. The experiments tried a variety of odors, including vanillin and decanoic acid, and used an electroencephalogram (EEG) to monitor brain activity.
A higher level of consciousness meant a greater response to smells.
Indeed, after three months, out of 16 patients who reacted to smells, 10 regained consciousness. By comparison, only two of the 12 patients in the group had no response to olfactory stimuli.
However, even in this latter group, there were some interesting brain patterns: in particular, higher functional brain connectivity, which is associated with sleepiness and relaxation, lower alpha and beta connectivity compared to healthy controls, and brainwaves associated with alertness and relaxation. active thinking. .
This has only been observed with the smell of vanillin, and the researchers believe that there may be some link between enjoyment of the smell and the likelihood of people with DoC reacting to it.
“Theta connectivity may be a neural correlate of olfactory awareness in DoC patients, which may help assess awareness and contribute to therapeutic strategies,” the researchers wrote.
Our olfactory systems work differently than other sense organs because they do not use the thalamus, the part of the brain that is a kind of relay station associated with consciousness. The researchers say smells have a more direct connection to the forebrain, which could be helpful in this context.
And all of this plays a role in our understanding of consciousness, the brain’s response to smell, and how they might be related. However, there is a lot more work to be done first with larger groups of people and a wider range of scents.
The next step is to find out why this link exists. Researchers suggest that with a lower level of consciousness, we lose the ability to process odors normally, but we’re not sure yet.
“Future studies should track recovery of consciousness after olfactory evaluation over a longer period,” the researchers wrote. “Future studies should also include indicators of temporal frequency or olfactory evoked potentials, which will complement our understanding of olfactory processing.”
The study is published in the journal Frontiers. in Neurology.
Source: Science Alert
