Persistent effects on sense of smell after Covid-19 infection
Dr Nixon Abraham’s group of researchers from IISER Pune, in collaboration with researchers from B J Government Medical College and Sassoon General Hospitals Pune, reported on persistent olfactory learning deficits
Pune In a new paper published in March 2023 in the journal, “Current Research in Neurobiology”, Dr Nixon Abraham’s group of researchers from Indian Institute of Science Education and Research (IISER) Pune, in collaboration with researchers from B J Government Medical College and Sassoon General Hospitals Pune, reported on persistent olfactory learning deficits during and after Covid-19 infection.
The team conducted a high-precision, quantitative assessment of the ability to smell in four groups of people namely, symptomatic Covid-19 patients, asymptomatic Covid-19 carriers, those who recovered from Covid-19 infection, and healthy individuals. Dr Abraham said, “Participants in the study were presented with certain odours at intervals and the following aspects were looked for and measured quantitatively by the team: did the participants detect the odour correctly, were they able to tell apart one odour from another (olfactory matching accuracy), and were there any changes to olfactory matching accuracy after multiple sessions (olfactory learning).”
The team then compared and analysed the data that they had gathered through the olfactometer from each of these sessions, which together represented about 12,000 behavioural read-outs from a total 200 participants. Dr Abraham said, “Such precise quantification of the sense of smell - where we were able to get information on both the sensory and cognitive deficits caused by Covid-19 infection - was made possible because of the olfactometer that we custom-built. Its design prevents cross-contamination between different tests, which is a unique feature, and also allows us to generate stimuli of varying complexity by using multiple odours.”
Dr Abraham’s group of researchers works on deciphering the neural circuits involved in olfaction, or the sense of smell, with the goal of obtaining insights into animal behavioural responses, decision-making processes, and brain function in health and disease. When losses or deficits in the sense of smell due to Covid-19 infection had just about begun to be reported, Dr Abraham’s group opted to probe the matter and initiated a collaboration with doctors from B J Government Medical College and Sassoon General Hospitals in Pune.
For experiments to study the sense of smell, the group employs an olfactometer, a device to deliver odour stimuli in a controlled manner. Working through the early months of the Covid-19 pandemic in 2020, the group custom-built a special version of the olfactometer with built-in safety precautions for preventing the transfer of infection during the study, and was able to conduct an olfactory fitness study in Covid-19 patients. The results were published in the October 2020 edition of “e-Clinical Medicine” and identified deficits in the sense of smell in over 80% of asymptomatic Covid-19 carriers.