Unlocking the mysteries of the brain

August 26, 2020

How does our brain store information?

Seeking an answer, researchers at CHU Sainte-Justine Hospital and Université de Montréal have made a major discovery in understanding the mechanisms underlying learning and memory formation.

The results of their study are presented today in Nature Communications.

Led by Professor Roberto Araya, the team studied the function and morphological transformation of dendritic spines, tiny protrusions located on the branches of neurons, during synaptic plasticity, thought to be the underlying mechanism for learning and memory.

"We are very excited because this is the first time that the rules of synaptic plasticity, a process directly related to memory formation in the brain, have been discovered in a way that allows us to better understand plasticity and ultimately how memories are formed when neurons of the cerebral neocortex receive single and/or multiple streams of sensory information" said Professor Araya.

A neuronal "tree"

The brain is made up of billions of excitable nerve cells better known as neurons. They specialize in communication and information processing.

"Imagine a tree," said Araya. "The roots are represented by the axon, the central trunk by the cell body, the peripheral branches by the dendrites and finally, the leaves by the dendritic spines. These thousands of small leaves act as a gateway by receiving excitatory information from other cells. They will decide whether this information is significant enough to be amplified and circulated to other neurons.

"This is a key concept," he added, "in the processing, integration and storage of information and therefore in memory and learning."

Neurons amplify the "volume"

Dendritic spines serve as a contact zone between neurons by receiving inputs (information) of varying strength. If an input is persistent, a mechanism by which neurons amplify the "volume" is triggered so that it can better "hear" that particular piece of information.

Otherwise, information of a low "volume" will be further turned down so that it goes unnoticed. This phenomenon corresponds to synaptic plasticity, which involves the potentiation or depression of synaptic input strength.

"This is the fundamental law of time-dependent plasticity, or Spike-timing-dependent plasticity (STDP), which adjusts the strength of connections between neurons in the brain and is believed to contribute to learning and memory," said Sabrina Tazerart, co-author of the study.

While the scientific literature shows this phenomenon and how neurons connect, the precise structural organization of dendritic spines and the rules that control the induction of synaptic plasticity have remained unknown.

"Laws of connections"

Araya's team has succeeded in shedding light onto the mechanisms underlying STDP.

"Until now, no one knew how synaptic inputs (incoming information) were arranged in the 'neural tree' and what precisely causes a dendritic spine to increase or decrease the strength, or loudness, of information it passes on," the professor said. "Our goal was to extract "laws of synaptic connectivity" responsible for building memories in the brain.'"

For their study, his team employed preclinical models at a juvenile stage, a critical period for learning and memory in the brain.

Using advanced techniques in two-photon microscopy that mimic synaptic contacts between two neurons, the researchers discovered an important law related to the arrangement of information received by dendritic spines.

Their work shows that depending on the number of inputs received (synapses) and their proximity, the information will be taken into account and stored differently.

"We found that if more than one input occurs within a small piece of tree branch, the cell will always consider this information important and will increase its volume," said co-first author Diana E. Mitchell.

"A major discovery"

"This is a major discovery," added Araya.

"Structural and functional alterations of dendritic spines, the major recipients of inputs from other neurons, are often associated with neurodegenerative conditions, such as Fragile X syndrome or autism, as the patient can no longer process or store information properly," he said.

"This disrupts the logic of memory construction. Now, by understanding the mechanisms underlying the dynamics of dendritic spines and how they impact the nervous system, we will be able to develop new and better-adapted therapeutic approaches."
-end-


University of Montreal

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.