When Tali Weiss and her colleagues at the Weizmann Institute of Science found a patient that had an otherwise normal sense of smell, but with no apparent [olfactory bulb], they were surprised. In a serendipitous observation, the team was scanning a woman that was supposed to be a “healthy control” for a different study. When analyzing the MRI scan of that patient, the scientists found no OB at all. Curious, they enrolled more participants for this study, and after several scans, they found another woman without an OB who could smell just fine.
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As far as how smell is being processed in brains with no OBs, there are different hypotheses being considered. One possibility is that the neurons that usually compose the OB migrated; another possibility is that other parts of the olfactory circuit, like the upstream mitral cells, took over the OB’s responsibilities.
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Detecting anosmia early has not been a high priority medical goal. In fact, most people only realize they are not able to smell during their teenage years. These new results show that there might be a mechanism in which the brain is able to adapt to the lack of that structure.
