There is more parallel "traffic" in the human brain than in the animal brain

A Swiss study revealed that brain communications in Sapiens follow multiple pathways, unlike macaques and mice

Brain: Brain signals are sent from one source to a target, establishing a polysynaptic pathway that intersects multiple regions of the brain
Brain signals are sent from one source to a target, establishing a polysynaptic pathway that intersects multiple brain regions "like a road with many stops along the way" (Illustration: EPFL)

In a study comparing human brain communication networks with those of macaques and mice, researchers from the Federal Institute of Technology in Lausanne found that only the brains of male and female Sapiens transmit information via multiple parallel pathways, providing new insights into the evolution of mammals.
When describing brain communication networks, Alessandra Griffa, a senior postdoctoral researcher at EPFL, also loves using travel-related metaphors.
Brain signals are sent from one source to a target, establishing a polysynaptic pathway that intersects multiple brain regions “like a road with many stops along the way.”
The author explains that structural pathways of brain connectivity based on networks (or "roads") of neuronal fibers have already been observed.

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Brain: Alessandra Griffa is Research Coordinator at the Leenaards Memory Center of the Center Hospitalier Universitaire Vaudois
Alessandra Griffa is Research Coordinator at the Leenaards Memory Center of the Center Hospitalier Universitaire Vaudois
(Photo: CHUV)

Synergy between Federal Polytechnic of Lausanne and the Center Hospitalier Universitaire Vaudois

As a scientist in the Medical Image Processing Lab of the School of Engineering of the Federal Polytechnic of Lausanne and as a research coordinator at the Leenaards Memory Center of the Center Hospitalier Universitaire Vaudois, Griffa wanted to follow the models of information transmission to see how sent and received messages.
In a study recently published in “Nature Communications”, Alessandra collaborated with the manager of the Vaud MIP:Lab, Dimitri Van De Ville, and with the “FNS Ambizione” project grant holder Enrico Amico, to create “brain traffic maps” that could be compared between humans and other mammals.
To do this, the researchers used open-source diffusion (DWI) and functional magnetic resonance imaging (fMRI) data from humans, macaques, and mice, collected while the subjects were awake and at rest.
DWI scans allowed scientists to reconstruct “road maps” of the brain, while fMRI scans allowed different brain regions to be seen lighting up along each “road,” indicating that these pathways were transmitting neural information.

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Brain: Dimitri Van De Ville is Head of the Medical Image Processing Lab at the School of Engineering of the Federal Institute of Technology in Lausanne (Photo: Wyss Center)
Dimitri Van De Ville is Head of the Medical Image Processing Lab at the School of Engineering of the Federal Polytechnic of Lausanne
(Photo: Wyss Center)

Multimodal MRI data for information and graph theories

The researchers analyzed the multimodal MRI data using information and graph theory.
Alessandra Griffa states that it is precisely this new combination of methods that has allowed us to obtain unprecedented insights.
“The novelty of our study is the use of multimodal data in a single model that combines two branches of mathematics: graph theory, which describes polysynaptic 'roadmaps', and information theory, which maps the transmission of information or 'traffic' through the streets”.
And yet: “The basic principle is that messages transmitted from a source to a destination remain unchanged or are further degraded at each stop along the way, like the game of telephone we played as children.”
The researchers' approach revealed that in non-human brains information was sent along a single "route", whereas in humans there were multiple parallel routes between the same source and target.
Furthermore, these parallel paths were as unique as fingerprints and could be used to identify individuals.
“This parallel processing in the human brain is hypothesized, but has never been observed before at the whole-brain level.”, summarizes Griffa.

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Brain: Enrico Amico is SNSF Ambizione Fellow of the Federal Polytechnic of Lausanne and the University of Geneva
Enrico Amico is SNSF Ambizione Fellow of the Federal Polytechnic of Lausanne and the University of Geneva
(Photo: Enrico Amico)

Potential insights for evolution, medicine and computational neuroscience

Alessandra says the beauty of the model used by the researchers is its simplicity and the inspiration for new perspectives and avenues of research in evolution and computational neuroscience.
For example, the findings can be linked to the expansion of the human brain's volume over time, which has given rise to more complex connectivity patterns.
“We could hypothesize that these parallel information flows enable multiple representations of reality and the ability to perform human-specific abstract functions.”
The author adds that although this hypothesis is only speculative, given that the Nature Communications study did not involve any tests of the subjects' computational or cognitive abilities, these are questions she would like to explore in the future.

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Brain: in the brains of mice and macaques, information is sent along a single "road", while in humans there are multiple parallel paths between the same source and the target
In the brains of mice and macaques, information is sent along a single "road", while in humans there are multiple parallel paths between the same source and the target
(Photo: Alessandra Griff/CHUV-EPFL CC BY-SA)

“How information is combined and then processed to create something new”

“We've looked at how information travels, so an interesting next step would be to model more complex processes to study how information is combined and processed in the brain to create something new.”.
As a memory and cognition researcher, she is particularly interested in using the model developed in the study to investigate whether parallel transmission of information can confer resilience to brain networks.
Potentially, it could play a role in neurorehabilitation after brain injury, or in the prevention of cognitive decline in pathologies of advanced age.
“Some people age healthily, while others experience cognitive decline. We would like to see if there is a relationship between this difference and the presence of parallel information flows, and if these could be trained to compensate for neurodegenerative processes.".

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Brain: Researchers at the Federal Institute of Technology in Lausanne have discovered that only the human brain transmits information via multiple parallel pathways
Researchers at the Federal Institute of Technology in Lausanne have discovered that only the human brain transmits information via multiple parallel pathways (Photo: EPFL/iStock)