Over at the FromPyrgos blog, someone posted a comment about people at Basenotes.net thinking that they have “bionic noses.” This person, apparently, thinks that everyone more or less has the same sense of smell, assuming that they have normal physiology, presumably. While I don’t think the term bionic is necessarily best, and I think scent perception is more complex than simply detection ability (in particular, I think overall sensitivity or sensitivity to particular notes can change significantly in a short period of time), I will “step up” here and challenge this person’s criticism. First, I want to present scientific evidence that appears to demonstrate that one’s brain can actually change in order to “navigate” smells as well as space:
Neuroimage. 2013 Mar;68:55-62. doi: 10.1016/j.neuroimage.2012.11.044. Epub 2012 Dec 12.
Perfumers’ expertise induces structural reorganization in olfactory brain regions.
Delon-Martin C, Plailly J, Fonlupt P, Veyrac A, Royet JP.
INSERM U836, Institut des Neurosciences, Equipe Neuroimagerie et Perfusion Cérébrale, Grenoble F-38043, France. email@example.com
The human brain’s ability to adapt to environmental changes is obvious in specific sensory domains of experts, and olfaction is one of the least investigated senses. As we have previously demonstrated that olfactory expertise is related to functional brain modifications, we investigated here whether olfactory expertise is also coupled with structural changes. We used voxel-based morphometry to compare the gray-matter volume in student and professional perfumers, as well as untrained control subjects, and accounted for all methodological improvements that have been recently developed to limit possible errors associated with image processing. In all perfumers, we detected an increase in gray-matter volume in the bilateral gyrus rectus/medial orbital gyrus (GR/MOG), an orbitofrontal area that surrounds the olfactory sulcus. In addition, gray-matter volume in the anterior PC and left GR/MOG was positively correlated with experience in professional perfumers. We concluded that the acute olfactory knowledge acquired through extensive olfactory training leads to the structural reorganization of olfactory brain areas.
Copyright © 2012 Elsevier Inc. All rights reserved.
Hum Brain Mapp. 2012 Jan;33(1):224-34. doi: 10.1002/hbm.21207. Epub 2011 Mar 9.
Experience induces functional reorganization in brain regions involved in odor imagery in perfumers.
Plailly J, Delon-Martin C, Royet JP.
Neurosciences Sensorielles, Comportement, Cognition, UMR 5020 CNRS-Université Claude Bernard Lyon 1, Institut Fédératif des Neurosciences de Lyon, Lyon, France. firstname.lastname@example.org
Areas of expertise that cultivate specific sensory domains reveal the brain’s ability to adapt to environmental change. Perfumers are a small population who claim to have a unique ability to generate olfactory mental images. To evaluate the impact of this expertise on the brain regions involved in odor processing, we measured brain activity in novice and experienced (student and professional) perfumers while they smelled or imagined odors. We demonstrate that olfactory imagery activates the primary olfactory (piriform) cortex (PC) in all perfumers, demonstrating that similar neural substrates were activated in odor perception and imagination. In professional perfumers, extensive olfactory practice influences the posterior PC, the orbitofrontal cortex, and the hippocampus; during the creation of mental images of odors, the activity in these areas was negatively correlated with experience. Thus, the perfumers’ expertise is associated with a functional reorganization of key olfactory and memory brain regions, explaining their extraordinary ability to imagine odors and create fragrances.
Copyright © 2010 Wiley Periodicals, Inc.
Curr Biol. 2011 Dec 20;21(24):2109-14. doi: 10.1016/j.cub.2011.11.018. Epub 2011 Dec 8.
Acquiring “the Knowledge” of London’s layout drives structural brain changes.
Woollett K, Maguire EA.
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N 3BG, UK.
The last decade has seen a burgeoning of reports associating brain structure with specific skills and traits (e.g., [1-8]). Although these cross-sectional studies are informative, cause and effect are impossible to establish without longitudinal investigation of the same individuals before and after an intervention. Several longitudinal studies have been conducted (e.g., [9-18]); some involved children or young adults, potentially conflating brain development with learning, most were restricted to the motor domain, and all concerned relatively short timescales (weeks or months). Here, by contrast, we utilized a unique opportunity to study average-IQ adults operating in the real world as they learned, over four years, the complex layout of London’s streets while training to become licensed taxi drivers. In those who qualified, acquisition of an internal spatial representation of London was associated with a selective increase in gray matter (GM) volume in their posterior hippocampi and concomitant changes to their memory profile. No structural brain changes were observed in trainees who failed to qualify or control participants. We conclude that specific, enduring, structural brain changes in adult humans can be induced by biologically relevant behaviors engaging higher cognitive functions such as spatial memory, with significance for the “nature versus nurture” debate.
Copyright © 2011 Elsevier Ltd. All rights reserved.
If that was a bit too “technical, ” this report may help sum up the findings of the olfactory studies:
In previous research, the same team had shown that experienced perfumers could acquire the ability to imagine an odor clearly enough to “smell” it, even though it is physically absent, a capacity beyond the reach of “mere mortals.” The researchers had also noted that the greater the perfumers’ expertise, the lower the activity in the olfactory and mnesic regions of their brains. This seemingly paradoxical result is explained by the fact that neuronal communication becomes faster, more efficient and more specific in the brain of an expert.
In light of these initial findings, the researchers wondered if perfumers’ intensive training and practice also increased grey matter volume in the cerebral zones linked to olfaction. To answer the question, they performed MRI scans on 14 famous “noses,” including Jean-Claude Ellena and Daniel André. They also scanned the brains of 13 students from ISIPCA (Institut Supérieur International de la Parfumerie, de la Cosmétique et de l’Aromatique Alimentaire) in Versailles, as well as 21 “naïve” subjects with no olfactory knowledge or training.
The scans showed that grey matter in the primary olfactory cortex and orbitofrontal region neighboring the olfactory groove is greater in perfumers than in naïve volunteers. This cerebral development could be due to an increased number of dendritic arborizations1 or even a greater number of neurons, although this has yet to be proven.
The results also indicate that grey matter volume is directly correlated to experience. The more practice a perfumer has had, the greater the volume of these olfactory regions. On the other hand, the researchers noted that in naive subjects, these cerebral regions shrink considerably with age, a continual and generalized phenomenon among individuals with no training or experience. This suggests that the cerebral modifications observed in perfumers are due to practice rather than innate capacity.
These findings recall the structural modifications observed in other types of experts, including musicians, athletes, mathematicians, multilingual individuals and taxi drivers. All of these specialists reorganize and overdevelop the brain regions specific to their field of expertise. The human brain’s extraordinary capacity to adapt to environmental demands and transform with experience seems to be virtually unlimited.
Thus, the “bionic” idea seems inferior to the analogy of a weightlifter in this context. Now I’ll address my personal experiences. When I began this “hobby” in late 2007 I was about as much a “newbie” as one can imagine. The only major “advantage” I think I possessed is that I had embarked upon similar “journeys” in the past and realized that it would take time for me to understand what some online reviewers were trying to communicate. My sensitivity was low at first and notes as well as naturalness did not register at all. I was still in that developmental phase where scents either smelled entirely unique or were perceived in culturally-conditioned ways (for example, “old aftershave smell” or “orange Creamsicle” were ones I can remember). As I started to figure out the major notes, some of them seemed to “spike out” and often would become irritating, the most obvious example being lavender.
In order to study scents optimally, I bought several bottles that I thought would represent the major genres well, and that were generally well-received by Basenotes’ reviewers. After a few months, I was not only able to identify several notes fairly easily, but I noticed that I had a light-bulb-over-the-head moment when I smelled some new scents, thinking, “where have I smelled this before?” Soon, I realized that many scents were more or less “variations on theme.” What’s also interesting is that it usually took me about 10-15 minutes before I could figure out what scent I had already smelled that reminded me of the new one. Over the course of at least a year, I noticed that the time it took me to figure out what scent a new one reminded me of was cut down to perhaps five minutes, if I couldn’t determine that immediately.
Note that none of this is relevant for one’s enjoyment of a scent. There are some long-time members of Basenotes.net, for example, who probably couldn’t detect an obvious lavender note if their lives literally depended upon it (and on occasion they have admitted to this)! So, for whatever reason, it seems like the brains of some people never change in the way perfumers’ brains (or brain usage) do. My guess is that there is what one might call a “study factor” involved. That is, one must activate a certain part or parts of the brain that then aid in changing the brain’s structure or function. Whatever the case may be, I’ve found that a series of “Eureka” moments occur, such as, “that’s the sandalwood note that people rave about but is no longer to be found in recent designer releases.” Interestingly, over the last several days, most likely due to disrupted sleep patterns, I have noticed a major shift in my sense of smell; the first hour or two irritates my nose and throat, and there’s nothing pleasant about it (the type of scent doesn’t seem to matter), but eventually the scents settle down and they begin to seem more balanced. I’ll update this post with new developments !