Tuesday, June 6, 2023

Stressed, Depressed, and Social Unrest

If you thought we had reached a new horizon of mass social behavior modification via electronic drugs  (ie social media and the consumer surveillance apparatus), then just wait until the smells show up. Smells have a direct line to the limbic system, which is called so because it controls your limbs; it literally makes you move, and it also controls your mood. 

Incorporating scents into a VR environment suitable for spacefarers
Jan 2023, phys.org

Building scents into a VR nature environment: A user could walk near a river in the VR environment and not only hear the sound of rushing water but also smell wet grass. This is accomplished by using hitboxes, which are invisible shapes in the VR environment that activate when the avatar collides with them.

When conducting their study, Abbott and Diaz Artiles measured users' anxiety levels before and after experiencing a stress-inducing event. The results showed that adding olfactory stimuli not only decreased users' anxiety levels after experiencing heightened stress but also reduced their stress and anxiety levels from their baseline.

via Texas A&M University College of Engineering: Renee (Woodruff) Abbott et al, The impact of digital scents on behavioral health in a restorative virtual reality environment, Acta Astronautica (2022). DOI: 10.1016/j.actaastro.2022.05.025

Dogs can smell when we're stressed, study suggests
Oct 2022, phys.org
93.75% accuracy detecting changes in breath and sweat, before and after a fast-paced arithmetic task, along with self-reported stress levels, heart rate and blood pressure.

via Animal Behaviour Centre at Queen’s University Belfast, and Newcastle University: Dogs can discriminate between human baseline and psychological stress condition odours, PLoS ONE (2022). DOI: 10.1371/journal.pone.0274143

Chances are we can smell stress too, we're just not tuned-in to it. If you want proof, you can look at post-handshake-hand-sniffing behavior and think about how we're subconsciously measuring the stress levels of the people we shake hands with as a way to assess how we should react to them.  

And now for some thoughts about depression, anosmia and long covid:
Potential found to counter depression by restoring key brain rhythm
May 2023, phys.org

Effective communication between brain regions requires groups of neurons to synchronize their activity patterns in repetitive periods (oscillations) of joint silence followed by joint activity.

One such rhythm, called "gamma," repeats about 30 times or more in a second, and is an important timing pattern for the encoding of complex information, potentially including emotions.

Although its causes remain poorly understood, depression is reflected in gamma oscillation changes, according to past studies, as an electrophysiological marker of the disease in brain regions that manage the sense of smell, which have also been tied to emotions. 

"Our experiments revealed a mechanistic link between deficient gamma activity and behavioral decline in mice and rat models of depression, with the signal changes in the olfactory and connected limbic systems similar to those seen in depressed patients,"

Feeding an amplified olfactory bulb signal back into the brains of depressed rats restored normal gamma function in the limbic system, and reduced the depressive behaviors by 40 percent (almost to normal).

via NYU Grossman School of Medicine and University of Szeged in Hungary: Antal Berényi, Reinstating olfactory bulb derived limbic gamma oscillations alleviates depression-like behavioral deficits in rodents, Neuron (2023). DOI: 10.1016/j.neuron.2023.04.013.

Partially unrelated post script:
In case you're ever wondering how do they actually measure depression in mice, they get dunked in a bucket of water to see how long it takes for them to stop swimming -- the sooner they give up, the more depressed they are. 

Tuesday, May 30, 2023

Olfactory Camouflage aka Artificial Animal Smells

Endangered birds can be protected from predators with chemical camouflage
Oct 2022, phys.or

"Predator control"

In the first treatment sites, the researchers spread waterfowl odor in wetland areas. With the chemical camouflage, a new method successfully tested in Australia and New Zealand, the researchers studied whether great amounts of prey odor in the area prevents predators from finding the artificial bird nests.

In other areas, the researchers used eggs containing an aversive agent causing nausea with the goal of conditioning the predators to believe that the bird eggs were inedible. The researchers also used control sites which they visited as frequently as the treatment sites for controlling a potential disturbance effect.

The study showed that especially the chemical camouflage decreased the predation of the artificial waterfowl nests by red foxes, but a similar effect was not observed with raccoon dogs, a harmful invasive species to Finland.

"Red foxes might rely more on their sense of smell to find bird nests, while the raccoon dog might find the nests by happenstance when they move in the area," says Senior Researcher Vesa Selonen from the University of Turku, Finland.

via University of Turku: V. Selonen et al, Protecting prey by deceiving predators: A field experiment testing chemical camouflage and conditioned food aversion, Biological Conservation (2022). DOI: 10.1016/j.biocon.2022.109749

Thursday, April 6, 2023

Non-Invasive Behavior Modification

Can someone say "mind-control deodorant"?

Once we learn to activate olfactory receptors through the eyes with lasers, you'll be "tuned" before you enter large gathering spaces to be more socially compatible with the other occupants.
Researchers identify neurons that 'learn' to smell a threat
Jan 2023, phys.org

Researchers found that "inhibitory" neurons (nerve cells that act by silencing their synaptic partners) in an area of the brain responsible for interpreting social smells become highly active and change their function when males repeatedly meet and increase their territorial aggression. By disrupting the neurons associated with neuroplasticity—learning—in the accessory olfactory bulb, researchers revealed that territorial aggression decreased, linking changes to cellular function in the pheromone-sensing circuity of the brain to changes in behavioral responses to social threats.

"It abolished the ramping aggression that is typically exhibited," said Zuk. "It indicates that this early sensory inhibitory neuron population plays a critical role in regulating the behavioral response to social smells."

via University of Rochester Medical Center: Kelsey E. Zuk et al, Arc-Expressing Accessory Olfactory Bulb Interneurons Support Chemosensory Social Behavioral Plasticity, The Journal of Neuroscience (2023). DOI: 10.1523/JNEUROSCI.0847-22.2022

Totally unrelated image credit: I'm endlessly fascinated with psychoanalyzing the artificial mind, in this case, one which cannot understand what fingers are: AI Art - A Person Who Conceals Their Face with their Hands AKA Damn Fingers - 2023

Scientists show that odors from other people's sweat can help treat social anxiety
Mar 2023, phys.org

Social anxiety was reduced when patients underwent mindfulness therapy while exposed to human 'chemo-signals', or what we commonly refer to as body odor, obtained from underarm sweat from volunteers.

Combining these chemo-signals with mindfulness therapy seem to produce better results in treating social anxiety than can be achieved by mindfulness therapy alone".

via the Karolinska Institute and The European Congress of Psychiatry taking place 25-28 March 2023, in Paris. https://epa-congress.org/

*This work is part of the EU-funded Horizon2020 project POTION ("Promoting Social Interaction through Emotional Body Odors") 4. 

Promoting social interaction through emotional body odours
The way chemistry influences human communication is one of the most intriguing and debated topics. More specifically, the nature of chemosignals and their sphere of influence on social interaction is a very important key to understanding human behaviour. POTION proposes a novel technological paradigm to delve deeper into understanding meaningful social interaction, combining new knowledge about the chemical composition of human social chemosignals together with a novel olfactory-based technology designed to drive social behaviour. A first challenging analysis on human chemosignals to delineate the chemical underpinnings of the emotions of happiness and fear will be carried out since they are the representative emotions that drive approach and avoidance behaviour, i.e. the fundamental building blocks of social interaction between individuals of the same species. Results of this analysis will be used to artificially synthetize the chemosignals of these two emotions, which will provide the basis of an innovative computer-controlled odour delivery system able to drive the approach-avoidance social strategy. This breakthrough device will be controlled in a closed loop by the social-emotional state of the subjects evaluated through a novel computational neural model. The POTION system will be applied and tested in both social and clinical scenarios. In the social scenarios, we venture to reveal how olfaction clues work in managing the feelings of trust, presence and inclusion, in both virtual, real, and social media contexts. In the clinical scenario, POTION will propose a new human chemosignal-based diagnosis and treatment for social anxiety, phobias and depression, which are known to all share impaired social functioning. POTION will provide further insight to the fundamental underpinnings of human behaviour with the goal to help establish healthy social relationships through trust, leading to an overall improvement in wellbeing.

Ancient Computers

Cerebral cortexes are cool and all, but the "dumber" parts of the brain have a lot of good secrets in there too.

Lost fish find their way, thanks to their 'ancient brain'
Dec 2022, phys.org

They put tiny translucent zebrafish, barely half a centimeter in length, in a virtual reality environment that simulates water currents.

The researchers expected to see activation in the forebrain -- where the hippocampus, which contains a "cognitive map" of an animal's environment, is located. To their surprise, they saw activation in several regions of the medulla, where information about the animal's location was being transmitted from a newly identified circuit via a hindbrain structure called the inferior olive to the motor circuits in the cerebellum that enable the fish to move. When these pathways were blocked, the fish was unable to navigate back to its original location.

These findings suggest that areas of the brainstem remember a zebrafish's original location and generate an error signal based on its current and past locations. This information is relayed to the cerebellum, allowing the fish to swim back to its starting point. This research reveals a new function for the inferior olive and the cerebellum, which were known to be involved in actions like reaching and locomotion, but not this type of navigation.

via Howard Hughes Medical Institute: Misha B. Ahrens, A brainstem integrator for self-location memory and positional homeostasis in zebrafish, Cell (2022). DOI: 10.1016/j.cell.2022.11.022

Image credit: Homotopical Topology by Fomenko and Fuchs

Friday, February 10, 2023


Sounds like a big deal. Also sounds like a great explanation for the phantom "Iso E Super" anosmia that isn't a full anosmia.

Researchers reveal an added layer of nuance in our sense of smell
Jan 2023, phys.org

They've discovered something called a depolarization lock to add to the standard combinatorial coding model used for odor detection, and it turns off the receptors when presented with high concentrations of an odor. 

You might already be familiar with this phenomenon for odors like violet and hydrogen sulfide (H2S). In the case of H2S, this receptor-deactivating behavior can be life-threatening, which is why you're supposed to wear a supplemental gas monitor, in addition to your nose, when entering areas suspected to contain high concentrations of the gas. 

^This write-up does a good job of explaining the fruit fly experiment that led to this discovery, as well as possible reasons why this would be needed for olfaction. 

via UC Santa Barbara: David Tadres et al, Depolarization block in olfactory sensory neurons expands the dimensionality of odor encoding, Science Advances (2022). DOI: 10.1126/sciadv.ade7209

Post Script:
In addition to Iso E Super, Hedione is another perplexing odorant that's in almost every fragrance formulation from floor cleaners to face cream, and yet most people can't actually smell it. Well, you can smell when it's NOT there, but you can't smell when it is. (Old post mentioning Hedione)

And if I'm reading this correctly, it sounds like someone with a hypersensitive nose might be more likely to lose their sensitivity altogether. I seem to have some kind of hyperosmia myself, and yet when I go out to sample perfume, I often can't smell anything at all. Take the same perfume, put it on a strip of paper and leave it on a table in my house for the next 3 weeks, and I will smell the whole bouquet revealed one at a time as the mixture breaks down. The theory being that if you're hypersensitive to a specific odorant, or all odorants for that matter, your "depolarization lock" will kick in at low concentrations. 

Post Post Script:
Hella synonyms for the musky odorant referred to above, in fact so many that I just wanted to list them here: Iso E Super, Tetramethyl acetyloctahydronaphthalenes is a synthetic ketone fragrance also known as octahydrotetramethyl acetophenone (OTNE) and by other commercial trade names such as: Iso E Super, Iso Gamma Super, Anthamber, Amber Fleur, Boisvelone, Iso Ambois, Amberlan, Iso Velvetone, Orbitone, Amberonne. It is a synthetic woody odorant and is used as a fragrance ingredient in perfumes, laundry products and cosmetics.
-Hall, John B. & Sanders, James Milton, "Perfume composition and perfume articles containing one isomer of an octahydrotetramethyl acetonaphthone", issued 1975

Neural Cartography

This first article doesn't sound like the cartography I came here for, but it's in the title so...
Researchers present insight into the neural cartography of smell
Oct 2022, phys.org

Honestly I'm unclear as to what this means; the endoplasmic reticulum has some mediating influence on the neural computations that turn olfactory receptor stimulus into the olfactory perception of a specific odorant?

"It is mind-blowing," said Dr. Lomvardas, also a professor of neuroscience and of biochemistry and molecular biophysics at Columbia's Vagelos College of Physicians and Surgeons. "This system found a way to create a genetically encoded, hard-wired means of transforming randomly-chosen receptor identity to a very precise target in the olfactory bulb."

Perhaps, olfactory neurons are not alone in the way endoplasmic reticulum stress organizes their wiring with downstream neurons. "If it turns out that all neurons do this, this discovery could help us understand much more about the brain," said Shayya.

via Mind, Brain and Behavior Zuckerman Institute at Columbia University:  Hani J. Shayya et al, ER stress transforms random olfactory receptor choice into axon targeting precision, Cell (2022). DOI: 10.1016/j.cell.2022.08.025

Here's another article that makes reference to "maps" but isn't actually about navigation...
Mapping the path from smell to perception
Nov 2022, phys.org

"The last frontier of sensory neuroscience"

Because previous studies of the olfactory cortex failed to find any logical organization among neurons there, many neuroscientists suspected information about odors was relayed randomly through the brain. But those studies examined connectivity patterns of just a few dozen neurons.

DNA-based brain-mapping technologies charting the way sensory information is routed between olfactory-processing parts of the brain including the olfactory bulb, which receives sensory information from the nose, the primary smell-processing hub called the piriform cortex, and several other brain regions that receive inputs from the olfactory bulb.

via Cold Spring Harbor Laboratory: Yushu Chen et al, High-throughput sequencing of single neuron projections reveals spatial organization in the olfactory cortex, Cell (2022). DOI: 10.1016/j.cell.2022.09.038

And finally, a little something about how we use olfaction to navigate...
Flies smell the motion of odors and use it to navigate, study finds
Nov 2022, phys.org

Flies can sense the direction of moving odor packets themselves, not just the wind.

Cool study design: They genetically modified fly antennae to detect light, then created fictive odor packets out of light and watched how the flies responded to these signals in both windless and windy environments.

via QBio Institute at Yale: Nirag Kadakia et al, Odour motion sensing enhances navigation of complex plumes, Nature (2022). DOI: 10.1038/s41586-022-05423-4

Friday, January 13, 2023

Smells Like Covid Part 2

It's been a couple years since the world learned the word "anosmia," so here's some updates:
(but don't forget this post about how parosmia worked with covid)

The first mass screening system for COVID cases has been developed with a sensitivity of 97%
Dec 2022, phys.org

Washing your hands with hydroalcoholic gel, smelling it and using a QR code to answer a short questionnaire. These very simple actions make up the world's first patented mass screening system for COVID cases.

Citrus fruits and apples are two of the first aromas that people with the SARS-CoV-2 virus stop detecting.

"Citrus" -- I don't remember seeing this at all, so I looked further into the report: "Based on the literature and habits of our Mediterranean study population, it was determined that the most suitable odoriferous substance was lemon." via Institute for Research in Fundamental Sciences in Iran and R DOty at U Penn: Moein, S. T. et al. Smell dysfunction: A biomarker for COVID-19. Int. Forum Allergy Rhinol. 10, 944–950 (2020). https://pubmed.ncbi.nlm.nih.gov/32301284/  -- This study used the University of Pennsylvania Smell Identification Test (UPSIT) which has 40 odorants; I can't read the paper because paywall, but I guess "citrus" or "lemon" is one of those odors. The paper wasn't meant to find the most prevalent non-detectable odor, but I guess it was just sitting there in the data?

"The antigen tests on the market have an average sensitivity of 80%, which means that the number of false negatives is 20%. What we have developed is not a diagnostic test, but a screening system that aims to detect the maximum possible number of positives and prevent false negatives," explained the researchers.

via Youcef Azeli et al, A machine learning COVID-19 mass screening based on symptoms and a simple olfactory test, Scientific Reports (2022). DOI: 10.1038/s41598-022-19817-x

Image credit: Stainless steel climate chamber at the Technical University of Denmark, Mikal Schlosser, 2022

Loss of smell following COVID linked to a person's immune reaction to the infection
Dec 2022, phys.org

They studied antibody levels in people infected during the early days of the pandemic—in all, they studied blood samples of 306 people who had donated blood for study after recovering from a COVID-19 infection. In comparing the antibody levels with other data provided by the donors and their doctors, the researchers determined that those people who had higher antibody levels tended to be the same people who had reported losing their sense of smell or taste. They found that such patients were twice as likely to lose one or the other sense as those who did not have higher-than-average levels of antibodies in their blood.

via Columbia University Irving Medical Center, the University of Pennsylvania, the National Institute of Alcohol Abuse and Alcoholism and the New York State Psychiatric Institute: Jonathan B. Overdevest et al, Chemosensory deficits are best predictor of serologic response among individuals infected with SARS-CoV-2, PLOS ONE (2022). DOI: 10.1371/journal.pone.0274611

Scientists find key reason why loss of smell occurs in long COVID-19
Dec 2022, phys.org

The reason some people fail to recover their sense of smell after COVID-19 is linked to an ongoing immune assault on olfactory nerve cells and an associated decline in the number of those cells, a team of scientists led by Duke Health report.

via Duke University Medical Center: John Finlay et al, Persistent post-COVID-19 smell loss is associated with immune cell infiltration and altered gene expression in olfactory epithelium, Science Translational Medicine (2022). DOI: 10.1126/scitranslmed.add0484.

Post Script:
Nasal injections could treat long-term COVID-19–related smell loss
Jan 2023, phys.org

Using injections of platelet-rich plasma derived from a patient's own blood. In a trial of 26 participants, those who received the treatment were 12.5 times more likely to improve than patients who received placebo injections. 

"It's a nerve damage and nerve regeneration issue that we're dealing with," she said.

via Stanford: Carol H. Yan et al, Use of platelet‐rich plasma for COVID‐19–related olfactory loss: a randomized controlled trial, International Forum of Allergy & Rhinology (2022). DOI: 10.1002/alr.23116