Thursday, April 7, 2022

Smells Like News

Too many headlines, too little time.
Image credit: Smell Test, Win McNamee Getty Images, 2010

Smelling Disease
Monell Updates, Feb 2022

Led by Monell chemical ecologist Bruce A. Kimball, PhD, the research team is taking the innovative approach of classifying fever-inducing diseases based on their distinctive signatures of volatile compounds in urine and saliva.

via the Monell Chemical Senses Center: Millet P., Martin, T., Opiekun, M., Beauchamp, G.K., and Kimball, B.A. (2021). Differing Alterations of Odor Volatiles among Pathogenic Stimuli. Chem. Senses. 46: bjab030.

'E-nose' could someday diagnose Parkinson's disease by 'smelling' skin
Feb 2022,
Three odor compounds (octanal, hexyl acetate and perillic aldehyde) were significantly different between the two groups, which they used to build a model for PD diagnosis.

Next, the researchers analyzed sebum from an additional 12 PD patients and 12 healthy controls, finding that the model had an accuracy of 70.8% in predicting PD. The model was 91.7% sensitive in identifying true PD patients, but its specificity was only 50%, indicating a high rate of false positives.

Sorry to say but those might not be false positives...we've seen this before (they haven't been diagnosed yet).

via Department of Biomedical Engineering, Zhejiang University, Hangzhou: Wei Fu et al, Artificial Intelligent Olfactory System for the Diagnosis of Parkinson's Disease, ACS Omega (2022). DOI: 10.1021/acsomega.1c05060

Study identifies brain areas that support social semantic accumulation
Feb 2021,

Olfaction is a social sense, and more reasons why we're bad at naming smells, because as somewhat social words, we think of them in sentences not in words...

via CAS Key Laboratory of Behavioral Science in China and University of Trento in Italy: The brain network in support of social semantic accumulation. Social Cognitive and Affective Neuroscience(2021). DOI: 10.1093/scan/nsab003.

Odd smell: Flies sniff ammonia in a way new to science
Jun 2021,

They probed all three types of scent neurons in the flies' sensilla, but they didn't respond to ammonia. But the fly was obviously smelling it, based on its behavior. So the researchers realized there had to be a fourth scent neuron they hadn't known was there. And they found it—but it didn't seem to have the usual odor receptors on it. It was covered in ammonia transporter (Amt), a molecule that is known to allow ammonia in and out of cells.

No one had ever known a transporter molecule to also act as an odor receptor. But there it was. When they selectively killed off only that type of neuron, the flies did not respond to ammonia at all. And when the team forced scent neurons that don't normally respond to ammonia to express Amt on their surfaces, those neurons began responding to ammonia, too.

via University of Connecticut: Alina Vulpe et al, An ammonium transporter is a non-canonical olfactory receptor for ammonia, Current Biology (2021). DOI: 10.1016/j.cub.2021.05.025

Scientists on the scent of flavor enhancement
Jul 2021,

On smelling -- The less they knew about the reference aroma, the higher their chances of correctly identifying a match—a finding that suggests aroma detection involves learning, memory and cognitive strategy.

via The Ohio State University: Mackenzie E. Hannum et al, Non-food odors and the duality of smell: Impact of odorant delivery pathway and labeling convention on olfactory perception, Physiology & Behavior (2021). DOI: 10.1016/j.physbeh.2021.113480

Image credit: Zebrafish Brains - Stephanie Fore - 2021

Smells and emotions tug on the brain's habenula, or 'little rein'
Aug 2021,

Situational awareness:
Kavli Institute researchers showed that the habenula relays information from the outside world, such as smell and sight, along with internal states associated with emotions and learning, to the brain regions that control adaptive behaviors.

"It turns out that the habenula is an information hub," said Emre Yaksi, a professor at NTNU's Kavli Institute for Systems Neuroscience and head of the research group that did the study. "It integrates information about odors from the environment with the information from the limbic system, which is involved in emotional behaviors and learning."

"We argue that the habenula helps the brain to stop certain actions and communications across brain regions, in order to shift it to another mode that is better suited to the situation that the scent warns of," he said. 

via Norwegian University of Science and Technology: Ewelina Magdalena Bartoszek et al, Ongoing habenular activity is driven by forebrain networks and modulated by olfactory stimuli, Current Biology (2021). DOI: 10.1016/j.cub.2021.08.021

Your sense of smell may be the key to a balanced diet
Aug 2021,

Long story short -- if you just ate a cinnamon bun, you're less likely to want a cinnamon bun, because something about your olfactory acclimation, adaptation, attenuation... 

via Northwestern University: Laura K. Shanahan et al, Olfactory perceptual decision-making is biased by motivational state, PLOS Biology (2021). DOI: 10.1371/journal.pbio.3001374

New research 'sniffs out' how associative memories are formed
Sep 2021,

Neuroscientists at the University of California, Irvine have discovered specific types of neurons within the memory center of the brain that are responsible for acquiring new associative memories. Additionally, they have discovered how these associative memory neurons are controlled. 

Specific cells in the lateral entorhinal cortex of the medial temporal lobe, called fan cells, are required for the acquisition of new associative memories and these cells are controlled by dopamine, a brain chemical known to be involved in our experience of pleasure or reward.

In the study, researchers used electrophysiological recordings and optogenetics to record and control activity from fan cells in mice as they learn to associate specific odors with rewards. This approach led researchers to discover that fan cells compute and represent the association of the two new unrelated items (odor and reward). Without these cells, pre-learned associations can be retrieved, but the new associations cannot be acquired. Additionally acquiring new associations also requires dopamine.

"We never expected that dopamine is involved in the memory circuit. However, when the evidence accumulated, it gradually became clear that dopamine is involved," said Igarashi. "These experiments were like a detective story for us, and we are excited about the results."

via University of California, Irvine: Lee, J.Y. et al. Dopamine facilitates associative memory encoding in the entorhinal cortex. Nature (2021).

A universal law of physiology emerges from a professor's research
Oct 2021,

"Imagine you walk into a room someone has just painted. You'll likely think, 'This smells bad.' But the sensation decreases as you stay in there. The molecules don't disappear, not within that time frame. You've just gotten used to it."
-University of Toronto Engineering professor Willy Wong 

From an initial state, the organism's response activity rises to a peak response, then falls to a new final steady state. Wong has discovered that those three fixed points on the adaptation curve form a mathematical relationship that is obeyed across all sensory modalities and organisms.

"I compared 250 measurements of adaptation from different branches of sensory physiology and found that they are all compatible with a single, simple equation," says Wong.

via University of Toronto: Willy Wong, Consilience in the Peripheral Sensory Adaptation Response, Frontiers in Human Neuroscience (2021). DOI: 10.3389/fnhum.2021.727551

Scent of newborn infants blocks aggression in men, stimulates aggression in women
Nov 2021,

Dr. Eva Mishor from Prof. Noam Sobel's research group at Weizmann's Brain Sciences Department and the Azrieli Institute for Human Brain Imaging and Research have found that a molecule that can likely be sensed by all mammals, and that is found in abundance on the scalps of newborns, sparks brain and behavioral changes in adults who are exposed to it, affecting women one way, and having the opposite effect on men.

The finding is among the first to provide a direct link between human behavior and a single molecule picked up through the sense of smell. Furthermore, the diametrically opposed change it effected in women and men sheds new and surprising light on the mediating role sex plays in olfactory perception and its resulting neurological processes.

They're talking about pheromones, which as far as we know, do not work in humans. Apparently that has changed now?

The odor is hexadecanal, or HEX, and although you can't smell it, if you sniff it, it will affect your behavior. We already know it affects mice, but humans not so much. Not until now that is. We also know, through less-scientific means, that the only universally-liked smell for all people everywhere is the baby's head. 

via Weizmann Institute of Science: Eva Mishor et al, Sniffing the human body volatile hexadecanal blocks aggression in men but triggers aggression in women, Science Advances (2021). DOI: 10.1126/sciadv.abg1530

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