Scientists find brain plasticity assorted into functional networks

February 4, 2016, Virginia Tech
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

Brain activity linked to stress changes chemical codes

April 24, 2018
Five years ago, a team of University of California San Diego neurobiologists published surprising findings describing how rats' brain cells adopted new chemical codes when subjected to significant changes in natural light ...

Scientists develop new method that uses light to manage neuropathic pain in mice

April 24, 2018
For patients with neuropathic pain, a chronic condition affecting 7 to 8 percent of the European population, extreme pain and sensitivity are a daily reality. There is currently no effective treatment. Scientists from EMBL ...

Animal cyborg—behavioral control by activating 'toy craving' circuit

April 24, 2018
Children love to get toys from parents as presents. This craving for objects also underlies object hoarding disorders and shopping addiction. However, the biological causes of object pursuit have remained unknown. Part of ...

In Huntington's disease, heart problems reflect broader effects of abnormal protein

April 24, 2018
Researchers investigating a key signaling protein in Huntington's disease describe deleterious effects on heart function, going beyond the disease's devastating neurological impact. By adjusting protein levels affecting an ...

Heading—not collisions—cognitively impairs players

April 24, 2018
Worse cognitive function in soccer players stems mainly from frequent ball heading rather than unintentional head impacts due to collisions, researchers at Albert Einstein College of Medicine have found. The findings suggest ...

Imagined and actual movements are controlled by the brain in the same way

April 24, 2018
A new study from Karolinska Institutet in Sweden shows that imagined movements can change our perception in the same way as real, executed movements do. The research, which is presented in the scientific journal Nature Communications, ...

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.