Summary: A new study sheds light on how our sense of smell is affected by the decrease of neurons in our noses as we age.
Source: eLife.
Our noses may be able to adapt themselves to tell the brain, as efficiently as possible, about the most typical smells in our environment, suggests new research published in eLife.
The findings contribute to our understanding of how and why the mammalian nose adapts to smells. They could also help us understand how decreases in the number of neurons in the nose over a lifetime affect our sense of smell as we age.
The nose senses smells when molecules drift from nearby objects and activate specialised cells called receptor neurons. In the noses of mice, there are about 10 million receptor neurons which are split into over 1,000 types that each respond differently depending on what molecules they detect. Each receptor neuron is activated by many different smells, and each smell activates many different types of receptors. This means that to understand a smell, the brain needs to read the overall pattern of activation, or ‘coding’, across the different receptor types.
“Some types of receptor neurons in the nose are used more often than others, depending on the animal’s species,” says lead author Tiberiu Tesileanu, Associate Research Scientist in the neuroscience group at the Center for Computational Biology at the Flatiron Institute, US. “Recent experiments have also shown that the way different receptor types are used can change when animals are exposed to different smells. In our current study, we set out to explain these findings and build a model that can predict the observed biases in how receptors are used.”
Tesileanu and his team, Simona Cocco and Remi Monasson from France, and Vijay Balasubramanian, US, built a model for the distribution of receptor types. The model assumes that the nose can adapt itself to tell the brain, in the most efficient way possible, about common smells in our surroundings. “For instance, the receptor types activated by variable smells are important because they convey a lot of information to the brain about this variability, and are more abundant in the nose because of this,” Tesileanu explains. “To our knowledge, this is the first time that such ‘efficient coding’ ideas have been applied to explain patterns in the use of receptor neurons by the nose.”
He adds that theoretical and experimental scientists will need to do more work to measure the kinds of smells that are typical in our environments, and how human receptor neurons detect them.
Additionally, given the amount of information available regarding the relationship between receptors and natural odour statistics, further experiments could be designed that change the environment in specified ways and then measure the change in the amount of receptor neurons in the nose. “Comparing the results of these experiments to the changes predicted by our model would provide a strong test of how well these neurons take information to the brain when they first detect a new smell,” concludes senior author Vijay Balasubramanian, Cathy and Marc Lasry Professor at the University of Pennsylvania, US.
Funding: Simons Foundation, Aspen Center for Physics, Swartz Foundation, National Science Foundation, US-Israel Binational Science Foundation funded this study.
Source: Emily Packer – eLife
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Open access research for “Adaptation of olfactory receptor abundances for efficient coding” by Tiberiu Tesileanu, Simona Cocco, Remi Monasson, and Vijay Balasubramanian in eLife. Published February 26 2019.
doi:10.7554/eLife.39279
[cbtabs][cbtab title=”MLA”]eLife “New Insight on How the Nose Adapts to Smells.” NeuroscienceNews. NeuroscienceNews, 26 February 2019.
<https://neurosciencenews.com/olfaction-adaption-10823/>.[/cbtab][cbtab title=”APA”]eLife (2019, February 26). New Insight on How the Nose Adapts to Smells. NeuroscienceNews. Retrieved February 26, 2019 from https://neurosciencenews.com/olfaction-adaption-10823/[/cbtab][cbtab title=”Chicago”]eLife “New Insight on How the Nose Adapts to Smells.” https://neurosciencenews.com/olfaction-adaption-10823/ (accessed February 26, 2019).[/cbtab][/cbtabs]
Abstract
Adaptation of olfactory receptor abundances for efficient coding
Olfactory receptor usage is highly heterogeneous, with some receptor types being orders of magnitude more abundant than others. We propose an explanation for this striking fact: the receptor distribution is tuned to maximally represent information about the olfactory environment in a regime of efficient coding that is sensitive to the global context of correlated sensor responses. This model predicts that in mammals, where olfactory sensory neurons are replaced regularly, receptor abundances should continuously adapt to odor statistics. Experimentally, increased exposure to odorants leads variously, but reproducibly, to increased, decreased, or unchanged abundances of different activated receptors. We demonstrate that this diversity of effects is required for efficient coding when sensors are broadly correlated, and provide an algorithm for predicting which olfactory receptors should increase or decrease in abundance following specific environmental changes. Finally, we give simple dynamical rules for neural birth and death processes that might underlie this adaptation.
