Information Concentration Gradient Navigation

 

'Walk this way': Model explains how ants create trails to multiple food sources

Nov 2024, phys.org

https://phys.org/news/2024-11-ants-trails-multiple-food-sources.html

"If an ant has access to multiple food sources from its nest, it will initially make multiple trails to each of the sources."

Using computational simulations of ants searching for food, stochastic modeling and a system of partial-differential equations, and two subpopulations of foragers who wander around in search of food and returners who always return directly to the nest after finding food, the researchers observed that ants will selectively travel to the food source that is the shortest distance from its nest in an environment with multiple sources.

They found this collective behavior resides in the fundamental pheromone concentration gradient, where the returning ants would secrete less pheromones depending on how close the food source was to the nest, whereas more pheromones created a stronger scent.

via Florida State University Institute of Molecular Biophysics and Department of Mathematics and Statistics at Cleveland State University: Sean Hartman et al, Walk this way: modeling foraging ant dynamics in multiple food source environments, Journal of Mathematical Biology (2024). DOI: 10.1007/s00285-024-02136-2

https://dx.doi.org/10.1007/s00285-024-02136-2

Image credit: AI Art - Black Hole - 2025

The brain's processing paradox: Study quantifies the speed of human thought

Dec 2024,  phys.org

https://medicalxpress.com/news/2024-12-brain-paradox-quantifies-human-thought.html

This is pertinent to the article but such an important statement for understanding the brain, the body, evolution and of course chemosensation as the origin of brains:

They applied techniques from the field of information theory to a vast amount of scientific literature on human behaviors such as reading and writing, playing video games, and solving Rubik's Cubes, and quantified the speed of human thought at 10 bits per second. However, our bodies' sensory systems gather data about our environments at a rate of a trillion bits per second, which is 100 billion times faster than our thought processes.

But this question: Why does the brain process one thought at a time rather than many in parallel the way our sensory systems do?

"Human thinking can be seen as a form of navigation through a space of abstract concepts." Research suggests that the earliest creatures with a nervous system used their brains primarily for navigation, to move toward food and away from predators. If our brains evolved from these simple systems to follow paths, it would make sense that we can only follow one "path" of thought at a time.

via California Institute of Technology: Jieyu Zheng and Markus Meister. The Unbearable Slowness of Being: Why do we live at 10 bits/s?, Neuron (2024). DOI: 10.1016/j.neuron.2024.11.008.

https://dx.doi.org/10.1016/j.neuron.2024.11.008

How Memory Works for the Navigationally Challenged

If this chart makes sense to you, watch the rest of the video here:

The Uses of Memory in Olfactory Search, Antonio Celani Senior Researcher at ICTP, MaLGa Colloquia series, 20th February 2023 (this screenshot taken at 22min)

https://www.youtube.com/watch?v=vlnY7CZXtqw

He uses a quote from Flatland, come on. The presenter, Antonio Celani, was a researcher for the French National Research Council (CNRS) in 2000 - and in 1999, CNRS had a European Symposium on Olfaction and Cognition.

But in other news:

Neuroscientists find that animals replay incidentally encoded episodic memories

Jan 2024, phys.org

https://medicalxpress.com/news/2024-01-neuroscientists-animals-replay-incidentally-encoded.html

(This breakthrough in neuroscience research expands on a 2018 study that first reported evidence that animals can replay past events)

Researchers gave nine rats a list of odors using many common household spices, like cinnamon and paprika. Then, the rats were given a memory assessment where they were presented with two scents from the previous list. The rats must then choose which scent was the third-to-last scent presented.

placed rats in a radial maze where they were confronted with scented lids covering food. After the rats foraged through the maze, they were presented with the opportunity to report the third-to-last scent, having to draw from memory the previously presented scents.

The rats remembered multiple pieces of putatively unimportant information and later replayed a stream of episodic memories when that information was needed to solve an unexpected problem. The first and only trial run ended with a 100 percent success rate.

"We remember information even though it was seemingly unimportant when it was encountered. When we happen to need that information, we replay the stream of events to identify the information needed to solve our current problem."

via Indiana University: Cassandra L. Sheridan et al, Replay of incidentally encoded episodic memories in the rat, Current Biology (2024). DOI: 10.1016/j.cub.2023.12.043

https://dx.doi.org/10.1016/j.cub.2023.12.043

Hyperdimensional Navigation Syndrome

 

How humans use their sense of smell to find their way

Oct 2023, phys.org

https://medicalxpress.com/news/2023-10-humans.html

28 participants each entered a virtual three-dimensional smellscape four times. The placement of eight "odor objects" in the environment (smells like orange or banana) always stayed the same. What changed was where participants were placed in the virtual reality arena and which target odor they needed to find.

Results? "Human subjects can actually navigate spaces using their nose in the context of a particular type of virtual reality environment."

"We also demonstrated that this behavior was associated with the emergence of a particular neural signature indicative of what we might call 'cognitive maps.' This neural signature not only appeared in areas traditionally associated with navigation behavior, but also in olfactory-related brain regions."

Their findings suggest that these two sets of brain regions share a common spatial code, something that hadn't previously been known.

via University of Pennsylvania Jay Gottfried's lab: Clara U. Raithel et al, Recruitment of grid-like responses in human entorhinal and piriform cortices by odor landmark-based navigation, Current Biology (2023). DOI: 10.1016/j.cub.2023.06.087

https://dx.doi.org/10.1016/j.cub.2023.06.087

https://www.cell.com/current-biology/fulltext/S0960-9822(23)00873-4

Image credit: AI Art - Innovation - 2024

Coding for Information Overflow and Statistical Irregularity

Part of the "odor code" our brain uses to smell is tasked with overcoming the statistical irregularity caused by massive changes in airflow direction, speed, humidity, etc. as we pull that air through our nostrils. The cross-cancelling variables required in this effort are mentally exhausting to consider, never mind to calculate. But that's what we do when we smell:

How insects track odors by navigating microscale winds

May 2023, phys.org

https://phys.org/news/2023-05-insects-track-odors-microscale.html

"This is important because insects are typically tracking odor plumes in lower wind speeds, which indicates they are somehow making sense of the high directional variability they encounter," said Houle. "Turbulence intensity is strongly correlated with standard deviations in wind direction, which might be useful for future wind tunnel experimental designs aimed at recreating more 'natural' winds."

Based on their findings, Houle and van Breugel hypothesize an optimal range of wind speed and environmental surface complexity may exist to help insects locate an odor source.

via University of Nevada at Reno: Discovered near-surface wind direction is often highly variable over timescales of less than 10 minutes. They also found wind direction variability to be consistently higher in environments with greater surface complexity (urban areas) and lower at higher wind speeds.

Domestic cats' noses may function like highly efficient gas chromatographs

Jun 2023, phys.org

https://phys.org/news/2023-06-domestic-cats-noses-function-highly.html

Yet another example of how in olfaction nature is still ahead of technology:

Researchers created a 3D computer model of the cat nose and simulated how an inhalation of air containing common cat food odors would flow through the coiled structures. They found that the air separates into two flow streams, where one spreads slowly above the roof of the mouth on its way to the lungs, and a separate stream containing odorant moves rapidly through a central passage directly to the olfactory region toward the back of the nasal cavity.

In essence, the researchers suggest, the cat nose functions as a highly efficient and dual-purposed gas chromatograph.

via Ohio State University: Wu Z, Jiang J, Lischka FW, McGrane SJ, Porat-Mesenco Y, Zhao K. Domestic cat nose functions as a highly efficient coiled parallel gas chromatograph, PLoS Computational Biology (2023). DOI: 10.1371/journal.pcbi.1011

https://pubmed.ncbi.nlm.nih.gov/37384594/

Each nostril has a unique sense of smell, intracranial electroencephalogram study finds

Nov 2023, phys.org

https://medicalxpress.com/news/2023-11-nostril-unique-intracranial-electroencephalogram.html

10 subjects with intracranial depth electrodes were delivered an odor to the left, right, or both nostrils through an olfactometer device designed to deliver odors by computer control. Subjects had to identify the odor and indicate which nostril the odor came from. Subjects performed better in detecting and identifying odors in the bi-nostril condition compared to uni-nostril conditions.

Odor identity could be decoded from oscillations in the piriform cortex brain region via neural activity recorded from an intracranial electroencephalogram. The researchers observed that odor identity was encoded in two distinct, temporally segregated epochs in the bi-nostril condition, suggesting a separate smell interpretation occurs via each nostril, suggesting a possible computational advantage in processing odors in stereo. 

via University of Pennsylvania and the Barrow Neurological Institute of Phoenix: Gülce Nazlı Dikeçligil et al, Odor representations from the two nostrils are temporally segregated in human piriform cortex, Current Biology (2023). DOI: 10.1016/j.cub.2023.10.021

https://dx.doi.org/10.1016/j.cub.2023.10.021

Image credit: AI Art - Big Tunnel Full of Numbers - 2023

Insects for Olfactory Insight

Insects are such an important part of olfactory science because they smell with their antennae, which are outside their bodies, making it easier to study. Also, their brains are pretty simple, which makes it easier to study how the most complicated and least understood sense works.

Another reason insects are so important to olfactory science isn't really about olfaction, it's about malaria, and Zika, and West Nile, you name it. Mosquitoes are one of the main drivers of infectious disease around the world. And if we could only figure out how they use their sense of smell to find us, we could stop them from finding us and infecting us.

The first article shows you just how important this effort is --

Researchers build mosquito testing arena to discover how they find us over long distances

May 2023, phys.org

https://phys.org/news/2023-05-mosquito-arena-distances.html

"This is the largest system to assess olfactory preference for any mosquito in the world."

Using an ice-rink-sized (1,000 m3) outdoor testing arena in Choma District Zambia, researchers found that human body odor is critical for mosquito host-seeking behavior over long distances. They had six people sleep in single-person tents surrounding the arena over six consecutive nights, and they used repurposed air conditioner ducting to pipe air from each tent—containing the aromas of its sleeping occupant.

The testing arena contained a ring of evenly spaced landing pads that were heated to human skin temperature (35ºC). Each night, the researchers released 200 hungry mosquitoes into the testing arena and monitored their activity using infrared motion cameras.

• mosquitoes were not attracted to heated landing pads unless they were baited with CO2 
• human body odor was a more attractive bait than CO2 alone
• some people were more attractive to mosquitoes than others
• one volunteer with a strikingly different odor composition from the others consistently attracted very few mosquitoes
• people who were more attractive to mosquitoes consistently emitted more carboxylic acids probably produced by skin microbes
• the person who was least attractive to mosquitoes emitted less carboxylic acids but triple the amount of eucalyptol, which may be related to the person's diet
• the team identified 40 chemicals that were emitted by all of the humans, though at different rates.
• "It's probably a ratio-specific blend that they're following" 

via Johns Hopkins Bloomberg School of Public Health, Johns Hopkins Malaria Research Institute, and Macha Research Trust: Conor J. McMeniman, Human scent guides mosquito thermotaxis and host selection under naturalistic conditions, Current Biology (2023). DOI: 10.1016/j.cub.2023.04.050.

https://dx.doi.org/10.1016/j.cub.2023.04.050

Washing with different soaps could make you more or less attractive to mosquitoes

May 2023, phys.org

https://phys.org/news/2023-05-soaps-mosquitoes.html

"It's remarkable that the same individual that is extremely attractive to mosquitoes when they are unwashed can be turned even more attractive to mosquitoes with one soap, and then become repellent or repulsive to mosquitoes with another soap," says senior author and neuroethologist Clément Vinauger.

"What really matters to the mosquito is not the most abundant chemical, but rather the specific associations and combinations of chemicals, not only from the soap, but also from our personal body odors," says Vinauger.

via Virginia Tech: Clement Vinauger, Soap application alters mosquito-host interactions, iScience (2023). DOI: 10.1016/j.isci.2023.106667.

https://dx.doi.org/10.1016/j.isci.2023.106667

Perfume component helps lure male moth pests

Apr 2023, phys.org

https://phys.org/news/2023-04-perfume-component-lure-male-moth.html

Smells are so complicated: "Nonenal is a universal attractant that, by itself, doesn't have much of an effect, but when a certain percentage is added to the multi-chemical attractant mixture discovered nearly 40 years ago, it has a highly stimulatory effect."

(The researchers started examining ways to attract and then trap armyworm moths as part of a "mating disruption" strategy.)

via North Carolina State University: Ahmed M. Saveer et al, Nonanal, a new fall armyworm sex pheromone component, significantly increases the efficacy of pheromone lures, Pest Management Science (2023). DOI: 10.1002/ps.7460

https://dx.doi.org/10.1002/ps.7460

Good smells, bad smells: It's all in the insect brain

Aug 2023, phys.org

https://phys.org/news/2023-08-good-bad-insect-brain.html

I don't think I've ever heard the sense of smell referred to in this way: "While it is more of an aesthetic sense in humans, for insects, including locusts, the olfactory system is used to find food and mates and to sense predators."

It certainly is different, because in insects, their "palp" mouth triggers automatically to eat food just from the presence of some specific odors. I think we would usually see this difference in the context of the pheromone-receptor parts of our olfactory system, which don't actually work anymore in humans. Lots of animals, insects too, and beyond of course, have their behavior very strongly (could you call it irresistibly?) controlled by smells. 

Back to the study:

Interestingly, some of the locusts showed no response to any of the odors presented. They found that locusts only associated appealing scents with a food reward. Delaying the reward, they found that locusts could be trained to delay their behavioral response.

"All information received by our sensory apparatus, and their relevance to us, has to be represented by electrical activity in the brain. It appears that sorting information in between positive and negative happens as soon as the sensory signals enter the brain."

via McKelvey School of Engineering at Washington University in St. Louis: Rishabh Chandak et al, Neural manifolds for odor-driven innate and acquired appetitive preferences, Nature Communications (2023). DOI: 10.1038/s41467-023-40443-2

https://dx.doi.org/10.1038/s41467-023-40443-2

A non-invasive way to turn a cockroach into a cyborg

Sep 2023, phys.org

https://techxplore.com/news/2023-09-non-invasive-cockroach-cyborg.html

First, we made remote control roaches by smashing an electric circuit through their head. But now, it's as simple as slipping over their antennae a sleeve made of gold and plastic, and fixed in place by a blast of ultraviolet light, like plastic shrink-wrap.

Note to self -- insects don't get "injured," they get "damaged" -- "damaging cockroaches during attempts to control them results in a very short life expectancy, which then results in very little payoff for a lot of work".

via Nanyang Technological University in Singapore: Qifeng Lin et al, Resilient conductive membrane synthesized by in-situ polymerisation for wearable non-invasive electronics on moving appendages of cyborg insect, npj Flexible Electronics (2023). DOI: 10.1038/s41528-023-00274-z

https://dx.doi.org/10.1038/s41528-023-00274-z

Post Script: For a cockroach, and for all insects, their antenna is their nose, and so this is how we'll do it for humans too. (Except laser pulses through the retina are a likely candidate as well. Why not both?)

Image credit: AI Art - Old Man Standing next to Giant Hairy Ant Monster - 2023

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

https://phys.org/news/2022-12-lost-fish-ancient-brain.html

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

https://dx.doi.org/10.1016/j.cell.2022.11.022

Image credit: Homotopical Topology by Fomenko and Fuchs

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

https://medicalxpress.com/news/2022-09-insight-neural-cartography.html

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

https://dx.doi.org/10.1016/j.cell.2022.08.025

Image credit: AI Art - Number Two Number One - 2022

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

https://medicalxpress.com/news/2022-10-path-perception.html

"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

https://dx.doi.org/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

https://phys.org/news/2022-11-flies-motion-odors.html

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

https://dx.doi.org/10.1038/s41586-022-05423-4

Navigating the Information Gradient

Olfaction is so primitive in its function, that it's an ideal model for all kinds of things,  including navigation, but even moreso, information processing. The olfactory system might be the most effective information processing system we know of, and it's something we've barely begun to investigate. 

Chemotaxis doesn't make headlines often, but it should, because it's ultimately an information-processing problem (and the last time I checked, we were living in the Information Age).

Image credit: A smellmap of Amsterdam by Kate McLean circa 2017 at sensorymaps.com

Information processing constrains how E. coli bacteria navigate chemical gradients

Jan 2022, phys.org

https://phys.org/news/2022-01-constrains-coli-bacteria-chemical-gradients.html

Information that E. coli bacteria gather from their environment limits their performance at chemotaxis, the process by which they guide their movements in response to chemical signals.

And it's funny that they decided to use chemotaxis to test this, about using information efficiently, so in other words, chemosensation is a good model for testing and understanding how information is processed, biomimetically, if you will.

And why do we care? Because chemotaxis and olfaction are the same, at a primitive level. Not much has changed between the way E. coli navigates its environment and the way we do it.

"We wanted to test a broad biological hypothesis: that organisms make the best use of the information they acquire to perform behaviors and other functions. To investigate this, we needed a behavior simple enough that we could quantify how much information it needed and chemotaxis by the bacterium E. coli is a perfect example of such a behavior."

We realized we could measure the amount of information a bacterium was able to gather (in bits per second), while also understanding how much information they would need to navigate at the speeds observed."

To achieve this, they first set out to calculate the theoretical performance limit, which is the maximum speed at which a bacterium could navigate up a chemical gradient, based on a fixed rate at which it acquires information about chemical signals.

Finding the response strategy that maximized gradient-climbing speed with a fixed information cost resulted in the performance limit.

"We found that while climbing shallow gradients E. coli get very little information from their environment, about 0.01 bits/s.

via Yale: H. H. Mattingly et al, Escherichia coli chemotaxis is information limited, Nature Physics (2021). DOI: 10.1038/s41567-021-01380-3

http://dx.doi.org/10.1038/s41567-021-01380-3

Understanding how bacteria seek out and move towards food

Feb 2022, phys.org

https://phys.org/news/2022-02-bacteria-food.html

Chemotaxis is the process of attraction in the direction of a chemical gradient. The primary way that organisms control their motion and progressively move toward a target is by inhibiting tumbling when sensing that the chemical concentration is increasing along their current direction.

The research team used stochastic optimal control theory (instead of linear control theory) to find the best possible fully nonlinear sensing and control strategy of run-and-tumble motion (of E. coli) in environments with noisy chemical gradients.

And it looks like chemotaxis, which is the progenitor of olfaction. It is not a stretch to say that olfaction is a form of chemotaxis, and we move through a room to locate a source by using the pattern of its vaporized chemical essence in the air in the room. We calculate its distribution pattern (by stochastic optimal control theory, apparently^), predict the source, and move towards it, updating as we go. The only difference here is that we use legs, and a pretty complex limbic system, whereas E. coli just tumbles and tumbles in the chemovoid. 

via University of Tokyo Institute of Industrial Science: Kento Nakamura et al, Optimal sensing and control of run-and-tumble chemotaxis, Physical Review Research (2022). DOI: 10.1103/PhysRevResearch.4.013120

http://dx.doi.org/10.1103/PhysRevResearch.4.013120

Odour-Spatial Map - Diogo Matias - Champalimaud Foundation - 2021 [link]

Neurons in the olfactory cortex link smells to places

Feb 2022, phys.org

https://medicalxpress.com/news/2021-12-neurons-olfactory-cortex-link.html

Sometimes it's good to have someone else say things like this, for a change: 

The researchers focused on the primary olfactory cortex. "The olfactory system is unique among the senses," said the study's senior author, Zachary Mainen, a principal investigator at the Champalimaud Centre for the Unknown in Portugal. "Only olfaction has direct reciprocal connections to the hippocampal system, which is involved in memory and navigation."

It looks like neurons in the posterior piriform cortex (part of the primary olfactory cortex) are encoding place information just like hippocampal cells, and especially behaviourally significant spots. So it's real -- smells are not just smells, they are places and smells at the same time; we can't extricate them from each other, at least not for some brain cells.  

via Champalimaud Centre for the Unknown: Cindy Poo, Spatial maps in piriform cortex during olfactory navigation, Nature (2021). DOI: 10.1038/s41586-021-04242-3

http://dx.doi.org/10.1038/s41586-021-04242-3

Post Script:

How the brain navigates cities: We seem to be wired to calculate not the shortest path but the 'pointiest' one

Oct 2021, phys.org

https://techxplore.com/news/2021-10-brain-cities-wired-shortest-path.html

When people navigate through a city, they use not shortest path, but instead, pedestrians appear to choose paths that seem to point most directly toward their destination, even if those routes end up being longer, and this is called vector-based navigation.

via  Massachusetts Institute of Technology: Paolo Santi, Vector-based pedestrian navigation in cities, Nature Computational Science (2021). DOI: 10.1038/s43588-021-00130-y

http://dx.doi.org/10.1038/s43588-021-00130-y

Ant Ink and Infotaxis

The ant secretion methyl-4-methyl-pyrrole-2-carboxylate - "innocuous, faintly grassy, sulphurous, or fruitlike with a hint of naphtha", "an ichor of extraordinary power for the ants.

"They sweep their antennae back and forth in advance of the head to catch the odorant molecules. When a forager takes a long turn to the left and starts to run away from the track, its left antenna break out of the odor space first and is no longer stimulated by the guiding substance. In a few thousandths of a second, the any perceives the change and pulls back to the right." (p30-31) 

Biophilia: The Human Bond with Other Species 

E. O. Wilson, Harvard University Press, 1984

https://en.wikipedia.org/wiki/Biophilia_hypothesis

On Olfactory Navigation

I purposely read this book Supernavigators (2019) hoping to get some snippets on using our sense of smell to find things, and I wasn't disappointed. 

Humans were led to a random location within a room diffused with two odors. After brief sampling and spatial disorientation, they had to return to this location. Humans located the target with higher accuracy in the olfaction-only condition than in the control condition and showed higher accuracy than chance. 

-Jacobs, L.F.; Arter, J.; Cook, A.; and Sulloway, FJ. (2015). "Olfactory orientation and navigation in humans," PLOS 'One, 10(6), e0129387. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4470656/

Note there are two different versions of olfactory navigation -- one where you track an odor to its source (this relies heavily on bilateral input, aka stereo-olfaction) and the other, much more common for modern-day humans, is when you identify a place by its odor. We usually have our eyes open, and being the ocularcentric creatures that we are, we are likely to use visual cues and not even realize the odor-identity of a place. 

But it doesn't stop here, the rabbit hole continues, and this one goes all the way back to the golden days of behavioral science, when rats told us everything we wanted to know about ourselves: 

This report is ultimately based on rat experiments, with the "men" part being only conjecture by the researcher; and he concedes, "My argument will be brief, cavalier, and dogmatic. For I am not myself a clinician or a social psychologist. What I am going to say must be considered, therefore, simply as in the nature of a rat psychologist's ratiocinations offered free.

*Ratiocinations are another word for thoughts that also happens to remind the reader that we're talking about rats (he italicized the rat in ratiocinations).

The "mapmaking" happens during what they call "Vicarious Trial and Error" or "VTE'" and described as "the hesitating, looking-back-and-forth, sort of behavior which rats can often be observed to indulge in at a choice-point before actually going one way or the other." If you're not a scientist, you can probably just call it "thinking."

via Berkeley Labs: Tolman, E.C. (1948). "Cognitive maps in rats and men," Psychological Review, 55(4), p.189.

https://web.csulb.edu/~cwallis/382/readings/482/tolman.%20cognitive_maps_in_rats_and_men.1948.html

Image taken from the Silver Bible of Interior Design Standards

And with that, let us not forget that olfaction is the first sense. Before all the other ways we sense our environment, bacteria and fungi were using chemotaxis, detecting and navigating their way through a world of chemical gradients. The essay at the end of Hidden Scents, called "Olfactory Space and n-Dimensionality" tells the story of the primordial eukaryote as it chemo-taxis its way through evolution, past the multi-cellular organism, the chordata (animals with vertebrate), and eventually to the big-brained, smooth-skinned monkeys that we are today.

The neocortex is an outgrowth of the nose-brain, and not the other way around, and therefore olfaction can be a useful model for understanding the n-dimensional information network in which our brains operate. The world is typically understood as a 3-dimensional space, but in fact, from the perspective of the brain, we are navigating and interacting with an infinitely-dimensional information space. 

 

Spaced Out

Because of its key role in navigation, odor-detection and spatialization go hand-in-hand. A paper from McGill's Department of Psychiatry and the Douglas Mental Health University Institute gives evidence to support this relationship.

The hippocampus, which is the central location where spatial memories are "stored," is a key part of the olfactory system. The two – space and smell – are so closely related that they can become difficult to disentangle.

There is a great philosophical essay about the ontogeny of a salamander (see Hosek and Freeman below) in which a creature develops its identity (if questionably-sentient creatures can be said to do so) by way of olfaction. This creature, as with many others, interfaces its environment primarily by smell, especially in the beginnings of its life. The decisions that it makes then are in response to olfactory information, which through iterated reinforcement forms the foundation of its self.

I was so impressed by this idea that I was compelled to write a short essay myself about space, information and dimensionality, as narrated via the odyssey of the Eukaryote evolving through the epochs to its present-day instantiation as a self-aware human. It can be read here.

***

On this relationship between navigation and olfaction, I am reminded of a comment I received more than once when I was first telling folks about my book on smells – "What is it about architects and smells?" I studied both architecture and olfaction, and apparently, I'm not the only one.

That was something I couldn't answer at the time; I had never heard about it. As I began to meet more people involved in an olfactory occupation, be it writing about fragrance or designing olfactory experiences, I did notice a few interdisciplinary architects scattered among them.

Now it occurs to me quite clearly – architects are not experts at navigation so much as spatial perception in general, and specifically on moving through space. Whereas the painter is concerned with the way the eyes move through two dimensions, and the sculptor thinks about eyes moving in 3-D, the architect is concerned with the moving body.

The late architect Michael Graves made this the thrust of his speech as he opened his own School of Public Architecture at New Jersey's Kean University in 2015(ish?) – he told us that in designing a building, the human scale is the only one that matters. The way we feel in a space is the primary criterion when evaluating it. If you think about it, a building is like a body for our body.

***

Architects don’t have to learn much about proprioception, but maybe they should. Proprioception is the feeling that we have of our own bodies, where the parts are, how they're related, what they're doing, and whether we should move them out of the way of danger. (Anybody ever see the hand-smashing phantom limb trick? This is a good example of the power of proprioception.)

As we move through a building, our proprioception recognizes and records not only our own bodies, but the “bigger body” that we're in, whether it’s a building or a backyard. Before there was such a thing as architects or buildings (i.e., before we were human), we used olfaction as a way to calibrate our proprioception, and to navigate this bigger body that we’re in.

It seems I’ve done a pretty good job of navigating myself into the part of this post that I now have no idea how to get out, so I’ll have to leave it there. Architecture and olfaction make a good pair.

Notes:

Good spatial memory? You're likely to be good at identifying smells too

Oct 2018, phys.org

Louisa Dahmani et al, An intrinsic association between olfactory identification and spatial memory in humans, Nature Communications (2018). DOI: 10.1038/s41467-018-06569-4

Hosek R J & Freeman W J (2001). Osmetic Ontogenesis, or Olfaction Becomes You: The Neurodynamic, Intentional Self and Its Affinities with the Foucaultian/Butlerian Subject. Configurations 9: 509–541.

Michael Graves College

School of Public Architecture, Kean University

The Rubber Hand Illusion

BBC, 2010

Avian Navigation

Pigeons were fitted with mini Ticka watch cameras in 1908 by Dr Julius Neubronner to take aerial photos.

Smelly clue to bird navigation skills

Aug 2017, BBC

Researchers from the universities of Oxford, Barcelona and Pisa temporarily removed seabirds' sense of smell before tracking their movements. … They found the birds could navigate normally over land, but appeared to lose their bearings over the sea. … This suggests that they use a map of smells to find their way when there are no visual cues.

-BBC

Is there ever such thing as an animal that doesn’t use smell to navigate? Or anything for that matter? Humans use smell to “navigate.” We find the nipple by smell. We find mates by smell. (This is one of the few things about “pheromones” that’s unequivocally evidenced – it’s not the pheromones, and besides we don’t have pheromone receptors, but we do tend to like smells from people with compatible immune systems.) I really love how Alexandra Horowitz, in her book Being A Dog, describes the dog actively mapping its environment by its smells. I like how pet detectives find your escaped cat by drizzling your own urine outside your apartment complex so they have a point of familiarity to home-in on. And how could you not love this Florida woman who bottled her own scent so she could be found later as an Alzheimer’s wanderer.

Getting At the Collapsed Dimension

aka Disembodied Navigation of High Dimensional Reality

Alex Grey – Sacred Mirrors

Oops. I just dropped a clear thumbtack on a white floor. I used to hate that, until I learned the trick. You have to collapse the dimension.

Without hesitation, I drop to the ground, lowering my plane of vision until I’m sideways, eyesight scooting across the surface of the floor, until – there it is; I found my thumbtack.

From above, the visual information of the tack is similar to that of the floor. There’s no edges to be distinguished. Viewing the floor as a one-dimensional line (once your head is level with the floor) instead of a two-dimensional plane (as seen from above) makes the thumbtack plain-as-day. The thumbtack is then the only thing that penetrates into the second dimension – it is the only thing that raises above the floor.

If what you’re trying to do is disentangle the information of the tack from the information of the floor, then reducing the information of one make the remaining asymmetry obvious. A floor is essentially 2-D, and a tack is 3-D. And by “collapsing” your visual field to 1-D (by now seeing it as a line stretching above and below you, with the floor on one side and everything else on the other), the “leftover dimension” of the tack becomes immediately apparent. This is not so much about science-fiction space-folding dimensionality, but about information in general.

In the highly abstract, “disembodied” discipline of information science, dimensionality is not about space, or what I like to call body space. Body space is the three dimensions we are so familiar with, it is a volume and we are in it. But this is only one way of using dimensionality. (The imaginings of Flatland will only get us so far.) In essence, a dimension is a line of potential measurements. It doesn’t have to be about direction like NSEW. It can be in lightness or darkness, as in the one-dimensional measurement of the rods in our eyes. The spectrum of colors is another one-dimensional measurement used for seeing. Together, these two dimensions can generate a third piece of information which is the point in-between the two (and is the difference between pink and navy blue). This is now a measurement of the two measurements. The very idea of dimensionality is for creating this information space as a way for recognizing and manipulating complex patterns in our environment.

Color uses three dimensions, which are lightness/darkness, red-blue (rainbow spectrum), and brightness/dullness (similar to but not the same as light/dark). So “color” is (according to art academia) a piece of 3-D information; it is a measure of the three measurements. And vision in general is not dependent on color alone, but other things, particularly spatial positioning. But let’s stick to color.

What happens when we compare color to smell? Things get different. Smells only have two dimensions, “good” and “bad”. Then again, and just as valid, smells can have infinite dimensions. Recognizing a smell as “good” or “bad” is the highly subjective alternative, and shows more about culture and the individual than it does the smell itself. There must be another way.

To date, there is no comprehensive, universal organizing principle for odors. Some attempts use a multidimensional odorspace, such as Henning’s prism. Theoretically, any smell can be categorized, or identified, as a point in a prism. The vertices of the prism are Flowery, Foul, Fruity, Spicy, Burnt, and Resinous. Something called “Fruity” will sit right in the corner of the prism. Other odors can be in-between two or more odors, so that “Citrus” might be somewhere between Fruity and Flowery (and just a bit towards Foul?).  This is how odors start to drift away from the vertices, and then the edges, and then from the planes themselves into the middle space of the prism. Again, each point, or odor, is now in-between all the odor-classifying vertices. Technically this is a hybrid model, because there are 6 primaries, but the corresponding odor-points are represented inside a 3-D form. (Please note that the original Henning’s odor prism was meant to deliver information on the edges and between the vertices; the smells were not meant to be read inside the prism but on its surface, making it only a 3- or 4-dimensional odor space.) [By the way, check out this Cabinet article on other ways of organizing scents.]

Hennings Odor Prism

There is another way one can imagine a wheel with 6 spokes, where the points at the end of the spokes are primary odors (popcorn, mint, lemon, etc.).  Every identifiable smell looks like a misshapen, spiderwebbed splat reaching further outwards towards the smells it is similar to, and sinking down to the middle where it isn’t. This is a hybrid also, for the final piece of information is a 2-D shape, based on 6 dimensions.

Let us try one more. Imagine a ball with spikes sticking out in hundreds of directions, each one a primary odor. Any given odor is understood as being “between” these hundreds of primaries, as a measurement of the hundreds of measurements.

Here’s an example of a Radar Chart.

This is the idea of a high dimensional information space. It’s a pretty alien idea to us body-users, but not to the algorithms that run our lives, and apparently not to the nose on our face. Thinking about how we categorize smells is perhaps a step in the direction of making ourselves more at home in high-d reality.