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 Waves Ahoy

We're getting a lot of amazing brain data from epilepsy science these days (like the first evidence of brain death under EEG). 

Because epilepsy patients undergo an entire week of EEG monitoring prior to treatment (so the doctors can "get familiar with" their brainwaves), other scientists ask to bother them with experiments that have nothing to do with epilepsy. Like olfaction experiments. So the patients volunteer to have the data from their brainwave monitoring used by researchers while they squirt smell molecules at their face. 

Image credit: Kosalos via Fractal Forums - Flower Hive - 2021

Olfactory processing in three distinct neural waves

Feb 2022, phys.org

https://medicalxpress.com/news/2022-02-olfactory-distinct-neural.html

Now we ask whether different oscillations represent distinct features of an odor, or if different odors are represented by different oscillations," Zelano said

They're talking about neural oscillations. 

Neurons in visual and auditory systems usually operate at a background hum of excitability, but when the brain is trying to see or hear something, these neurons are activated in sync.

But the olfactory cortex is hard to study because it's literally in the center of the brain (and that's because it is like the seed from which our big ass brain grew out of). Brainwaves can be detected non-invasively, so that's great. 

The low-frequency oscillations, termed theta waves, begin immediately after a volunteer sniffed and ended immediately afterwards. Theta waves were followed by two more sets of waves, beta (about 12-30 Hz) and gamma waves (above 30 Hz).

This raises the possibility of a two-step process, where the low-frequency waves "prime" the olfactory cortex and the high-frequency waves are responsible for olfactory processing.

"Low-frequency waves are used for communications between brain regions and high frequency oscillation is more involved in local computations, but it's very exciting to find a low-frequency oscillation motivating a high-frequency oscillation," said Guangyu Zhou, Ph.D., research assistant professor of Neurology and a co-corresponding author of the study.

-phys.org

Oh but this part is even better:

Further, the strength of the high-frequency waves was associated with volunteers' ability to correctly identify odors.

"This implies the higher-frequency oscillations are required to actually distinguish the odor one is smelling," Qiaohan Yang, MS, student in the Northwestern Interdepartmental Neuroscience Program (NUIN) and lead author of the study.

-phys.org

via Northwestern University's Comprehensive Epilepsy Center: Qiaohan Yang et al, Smell-induced gamma oscillations in human olfactory cortex are required for accurate perception of odor identity, PLOS Biology (2022). DOI: 10.1371/journal.pbio.3001509

http://dx.doi.org/10.1371/journal.pbio.3001509

Post Script, On Epilepsy:

Who knew that treating epilepsy would lead to such novel discoveries? Why is C. elegans or D. melonigaster so important for specific things, or how is the naming of the limbic system itself a kind of word-monster that grew out of our heavy reliance on rats during the concurrent explosion of olfactory science in the Behavioral era, and rats have a brain that is dominated by olfaction, and it basically controls the movements of their body, hence their limbs, and so the olfactory system was called the limbic system. Why rats? Why fruitflies? Why epilepsy? 

Life may actually flash before your eyes on death

Feb 2022, BBC News

https://www.bbc.com/news/world-us-canada-60495730

First-ever recording of a dying brain discovered by accident. 

"This was actually totally by chance, we did not plan to do this experiment or record these signals."

-BBC

This is also one of the reasons why it is important to care for every human equally, regardless of what happened to them. You're born without an immune system? We're keeping you alive as long as we can. Paraplegic? We're giving you wifi for your body. 

You have epilepsy? We're going to slap some electrodes to your head and monitor your brainwaves for a really, really long time, and figure out how to help you. Unless you have a heart attack in the headset, in which case we'll watch what happens, and use your accident to further the advancement of science. 

via Department of Neurosurgery, Henan Provincial People’s Hospital, Division of Neurosurgery, Vancouver General Hospital: Vicente Raul et al. Enhanced Interplay of Neuronal Coherence and Coupling in the Dying Human Brain. Frontiers in Aging Neuroscience 14 2022. DOI: 10.3389/fnagi.2022.813531.

https://doi.org/10.3389/fnagi.2022.813531

Why C. elegans? They have only 302 neurons, that's why.

Scientists Make Discovery

Olfactory neurons adapt to the surrounding environment

May 2022, phys.org

https://medicalxpress.com/news/2022-05-olfactory-neurons-environment.html

This title could have had way more clickbait. The news is that we have no idea what's going on with olfactory neurons. 

Not like it's ever been claimed; they just never seem to obey any sensical laws, and they're always doing things we can't understand, but now it seems that even basic assumptions about how they work are way off.

The scientists discovered an unsuspected variability in gene expression profiles depending on the expressed olfactory receptor and previous exposure to odors. 

And in a previous study, these scientists found that after stimulation of a receptor by an odorant molecule for less than an hour, the expression of the gene coding for this receptor decreased in the neuron, indicating a very rapid adaptation mechanism.

"While it was thought that the binding of an odorant molecule would only lead to the activation of the corresponding receptor, we discover that olfactory neurons drastically change their identity by modulating the expression of hundreds of genes after activation. And this new identity is again dependent on the expressed receptor. We are facing an unexpected, massive, rapid and reversible adaptation mechanism," explains Ivan Rodriguez, co-corresponding author of the study.

This work reveals that olfactory neurons are not to be considered as sensors simply passing from a resting state to a stimulated state, but that their identity is in permanent evolution, not only according to the expressed receptor but also according to past experiences. This discovery adds another level to the complexity and flexibility of the olfactory system. 

via Faculty of Science and the Faculty of Medicine of the University of Geneva: Luis Flores Horgue et al, Transcriptional adaptation of olfactory sensory neurons to GPCR identity and activity, Nature Communications (2022). DOI: 10.1038/s41467-022-30511-4

https://dx.doi.org/10.1038/s41467-022-30511-4

Image credit: Unexpected Outcome, by shironosov and Getty, 2022 - Three shocked scientists looking at the obtained substance expressing intense emotions [link]

Post Script:

Consider that the olfactory family of genes is evolving within us in real time. It's a huge group of genes, being the largest family there is, at 2% of the genome, and it's highly variable in the population, with a 30% variation from person to person. 

Do you remember that item we learned back when the Human Genome project came out, that we share over 90% of our genome with monkeys, and almost as much with bananas? Now consider that our individual olfactory apparatus is 30% different from that of other humans. There's a lot of action here in the olfactory system.

Just wait until we figure out that it's running our immune system, because that's when things will get really crazy.