Scientists find brain plasticity assorted into functional networks

February 4, 2016
Credit: Human Brain Project

The brain still has a lot to learn about itself. Scientists at the Virginia Tech Carilion Research Institute have made a key finding of the striking differences in how the brain's cells can change through experience.

Their results were published this week in PLOS ONE.

"Neurons can undergo long-term changes in to experience such as learning, emotions, or other activity," said Michael Friedlander, executive director of the Virginia Tech Carilion Research Institute. Friedlander co-authored the paper with his former graduate student and postdoctoral fellow, Ignacio Saez. "Neuroscientists have focused much of their attention on understanding the neuroplasticity of the connections between nerve cells called synapses."

Synapses, the specialized connections between , work by translating an electrical signal from one neuron into a chemical signal to modify the receiving neuron. The chemical signal triggers an electrical signal in the receiving neuron, and the process continues.

Synapses may become stronger or weaker by changing efficiency of the chemical communication process in response to repeated bouts of co-activation of the two interconnected neurons. This process, called synaptic plasticity, can cause changes that persist beyond the co-activation period for mere minutes through a lifetime.

Outside experience can be internalized as a physical reorganization of the brain's synaptic communication process. This is especially important during the brain's development but also throughout life as experiences such as learning continually modify the brain's synaptic circuitry.

"Until recently, scientists had thought that most synapses of a similar type and in a similar location in the brain behaved in a similar fashion with respect to how experience induces plasticity," Friedlander said. "In our work, however, we found dramatic differences in the plasticity response, even between neighboring synapses in response to identical activity experiences."

Friedlander and Saez reported that neurons whose excitatory synapses are in a certain states of plasticity, based on previous experiences, assort themselves into groups to converge onto specific individual neurons in the developing brain.

"Individual neurons whose synapses are most likely to strengthen in response to a certain experience are more likely to connect to certain partner neurons, while those whose synapses weaken in response to a similar experience are more likely to connect to other partner neurons," Friedlander said. "The neurons whose synapses do not change at all in response to that same experience are more likely to connect to yet other partner neurons, forming a more stable but non-plastic network."

The researchers observed this like-type synaptic plasticity buddy system in a rodent model, using an isolated part of the cerebral cortex responsible for processing vision. The scientists recorded electrical activity from after activating groups of neighboring neurons. They then compared that recording to the electrical activity elicited in response to the activation of only a single neighboring neuron. The synapses were trained by repeating the activation process, to mimic learning.

When the scientists applied a pharmacological agent to the neurons that blocked synaptic inhibition, they saw that training elicited more dramatic and varied plasticity at . The plasticity responses of different groups of on a given neuron were more similar when inhibition was blocked, which effectively grouped together like-type neurons by their learning responses.

"While we've known for years that neurons of similar types tend to richly interconnect, this is the first demonstration that such assortment processes apply to ," Friedlander said. "Such a result has implications for enhanced learning paradigms, as well as for better understanding the dynamic network properties of the large-scale neuronal networks in the living brain."

Explore further: Key mechanism discovered which prevents memory loss in Alzheimer's disease

More information: Ignacio Saez et al. Role of GABAA-Mediated Inhibition and Functional Assortment of Synapses onto Individual Layer 4 Neurons in Regulating Plasticity Expression in Visual Cortex, PLOS ONE (2016). DOI: 10.1371/journal.pone.0147642

Related Stories

Key mechanism discovered which prevents memory loss in Alzheimer's disease

January 26, 2016
Neurons communicate with one another by synaptic connections, where information is exchanged from one neuron to its neighbor. These connections are not static, but are continuously modulated in response to the ongoing activity ...

Memory in silent neurons

August 31, 2014
When we learn, we associate a sensory experience either with other stimuli or with a certain type of behavior. The neurons in the cerebral cortex that transmit the information modify the synaptic connections that they have ...

Modeling memory in the brain

May 18, 2015
Scientists at EPFL have uncovered mathematical equations behind the way the brain forms – and even loses – memories.

Neuroscientists reveal how the brain can enhance connections

November 18, 2015
When the brain forms memories or learns a new task, it encodes the new information by tuning connections between neurons. MIT neuroscientists have discovered a novel mechanism that contributes to the strengthening of these ...

First direct evidence for synaptic plasticity in fruit fly brain

December 2, 2015
Scientists at Cold Spring Harbor Laboratory (CSHL) have resolved a decades-long debate about how the brain is modified when an animal learns.

Recommended for you

Now you like it, now you don't: Brain stimulation can change how much we enjoy and value music

November 20, 2017
Enjoyment of music is considered a subjective experience; what one person finds gratifying, another may find irritating. Music theorists have long emphasized that although musical taste is relative, our enjoyment of music, ...

Deletion of a stem cell factor promotes TBI recovery in mice

November 20, 2017
UT Southwestern molecular biologists today report the unexpected finding that selectively deleting a stem cell transcription factor in adult mice promotes recovery after traumatic brain injury (TBI).

MRI uncovers brain abnormalities in people with depression and anxiety

November 20, 2017
Researchers using MRI have discovered a common pattern of structural abnormalities in the brains of people with depression and social anxiety, according to a study presented being next week at the annual meeting of the Radiological ...

Brain cell advance brings hope for Creutzfeldt-Jakob disease

November 20, 2017
Scientists have developed a new system to study Creutzfeldt-Jakob disease in the laboratory, paving the way for research to find treatments for the fatal brain disorder.

Neuroscience research provides evidence the brain is strobing, not constant

November 17, 2017
It's not just our eyes that play tricks on us, but our ears. That's the finding of a landmark Australian-Italian collaboration that provides new evidence that oscillations, or 'strobes', are a general feature of human perception.

Brain activity buffers against worsening anxiety

November 17, 2017
Boosting activity in brain areas related to thinking and problem-solving may also buffer against worsening anxiety, suggests a new study by Duke University researchers.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.