'Grassroots' neurons wire and fire together for dominance in the brain

October 24, 2012
Every time a neuron in the network fires, a dot is placed indicating the time (x-axis) and neuron (y-axis). The collection of dots show the overall dynamics in the network. This model shows how clustering provides more competitive dynamics, where clusters are winning and losing randomly in time. Credit: University of Pittsburgh

(Medical Xpress)—Inside the brain, an unpredictable race—like a political campaign—is being run. Multiple candidates, each with a network of supporters, have organized themselves into various left- and right-wing clusters—like grassroots political teams working feverishly to reinforce a vision that bands them together. While scientists know that neurons in the brain anatomically organize themselves into these network camps, or clusters, the implications of such groupings on neural dynamics have remained unclear until now.

Using mathematical modeling, two researchers from the University of Pittsburgh have found that neurons team up together to sway particular outcomes in the brain and take over the nervous system in the name of their preferred action or behavior. The findings will be published in the November print issue of .

"Through complex mathematical equations, we organized neurons into clustered networks and immediately saw that our model produced a rich dynamic wherein neurons in the same groups were active together," said Brent Doiron, assistant professor of mathematics.

Together with Ashok Litwin-Kumar, a PhD student in neural computation in Pitt and Carnegie Mellons's Center for the of Cognition, Doiron found that, like a political race, the brain's neurons divide into a collection of candidates (clusters) with various preferences, each with its own network of supporters (neurons) interacting on a competitive playing field (the ). The Pitt researchers' mathematical models show that few neural teams can be highly active and "in the lead" at any given time, advocating for their stimulus or response preference and suppressing the preferences of the other teams.

However, when Doiron and Litwin-Kumar introduced a stimulus to select only a few groups in the network, the competition quickly became unbalanced. Similar to selective funding during a campaign, the parties with "more campaign money" (neurons influenced by their preferred stimulus) had a higher probability of "winning the race" (or taking over the nervous system).

"We found that stimulation actually reduces the firing rate variability among neurons, an observation that is consistent with recent cortical readings," said Doiron. "Our results show that even weak stimuli can substantially change our balanced network dynamics, making brain dynamics much more predictable."

When there was no stimulus, Doiron and Litwin-Kumar saw that the landscape of winners and losers was very random in time, with clusters randomly transitioning from the lead position to secondary positions and vice versa, much like a contentious political primary race trying to decide the leader of a party.

These significant fluctuations over long periods of time mimicked recorded activity in the spontaneously active brain. While past models of unclustered brains could not capture this key dynamic, this new model gives a plausible explanation for how spontaneous neural activity arises and is maintained.

These results explore for the first time how the wiring of the nervous system can influence stochastic (or unpredictable) brain dynamics, especially when the brain is spontaneously active. Doiron said there has been significant research on how the brain responds to input—such as during tasks like remembering a phone number or grasping a cup. However, the neuroscience community has only just begun to think about what is happening in the brain when there are no inputs and the brain is seemingly idle.

"Unlike the quiet states of your computer between processing jobs, the brain has a highly variable and random political fight going on when there are no immediate tasks," said Doiron. "This fight likely consolidates factions and keeps specific networks well linked, a feature that can be crucial for proper brain functioning in driven states."

With their new models, Doiron and Litwin-Kumar plan to investigate how the spontaneous neural dynamics caused by these clustered impact the processing of a stimulus, helping them possibly understand new forms of biological-inspired computation. He said that is a new field with significant challenges ahead.

"A good start is to understand what is happening in the 's default spontaneous state, and from there a more comprehensive theory of neural cognition can be made," said Doiron.

Explore further: Researchers link neural variability to short-term memory and decision making

Related Stories

Researchers link neural variability to short-term memory and decision making

April 2, 2012
A team of University of Pittsburgh mathematicians is using computational models to better understand how the structure of neural variability relates to such functions as short-term memory and decision making. In a paper published ...

Researchers connect neurons to computers to decipher the enigmatic code of neuronal circuits

July 12, 2011
Machine logic is based on human logic. But although a computer processor can be dissembled and dissected in logical steps, the same is not true for the way our brains process information, says Mark Shein of Tel Aviv University's ...

Brain cell networks recreated with new view of activity behind memory formation

May 25, 2011
University of Pittsburgh researchers have reproduced the brain's complex electrical impulses onto models made of living brain cells that provide an unprecedented view of the neuron activity behind memory formation.

Astrocytes control the generation of new neurons from neural stem cells

August 24, 2012
Astrocytes are cells that have many functions in the central nervous system, such as the control of neuronal synapses, blood flow, or the brain's response to neurotrauma or stroke.

Recommended for you

New study reveals contrasts in how groups of neurons function during decision making

July 19, 2017
By training mice to perform a sound identification task in a virtual reality maze, researchers at Harvard Medical School and the Istituto Italiano di Tecnologia (IIT) have identified striking contrasts in how groups of neurons ...

Memory takes time, researchers conclude

July 19, 2017
How short-term memories become long-term ones has frequently been explored by researchers. While a definitive answer remains elusive, New York University scientists Thomas Carew and Nikolay Kukushkin conclude that this transformation ...

Researchers identify new target for chronic pain

July 19, 2017
Proteins must be in the right place at the right time in the cell to function correctly. This is even more critical in a neuron than in other cells because of its complex tree-like structure and its function. Researchers ...

Brains are more plastic than we thought

July 19, 2017
Practice might not always make perfect, but it's essential for learning a sport or a musical instrument. It's also the basis of brain training, an approach that holds potential as a non-invasive therapy to overcome disabilities ...

Healthy heart in 20s, better brain in 40s?

July 19, 2017
Folks with heart-healthy habits in their 20s tend to have larger, healthier brains in their 40s—brains that may be better prepared to withstand the ravages of aging, a new study reports.

Individual insight into brain networks

July 19, 2017
Harvard scientists have gained new insights into how the brain networks important for thought and remembering are organized in individual people, bringing the notion of using brain scans to help personalize medical treatments ...

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.