Featured Research

from universities, journals, and other organizations

Researchers find epileptic activity spreads in new way

Date:
January 24, 2014
Source:
Case Western Reserve University
Summary:
Biomedical engineers have found that epileptic activity can spread through a part of the brain in a new way, suggesting a possible novel target for seizure-blocking medicines. Evidence from a series of experiments and computer modeling strongly suggests individual cells in a part of the brain, known as the hippocampus, use a small electrical field to stimulate and synchronize neighboring cells, spreading the activity layer by layer.

Researchers in the biomedical engineering department at Case Western Reserve University have found that epileptic activity can spread through a part of the brain in a new way, suggesting a possible novel target for seizure-blocking medicines.

Evidence from a series of experiments and computer modeling strongly suggests individual cells in a part of the brain, known as the hippocampus, use a small electrical field to stimulate and synchronize neighboring cells, spreading the activity layer by layer.

The scientists report the discovery in the Journal of Neuroscience this week.

"We know there are several ways for neurons to talk with one another: chemical and electrical synaptic transmission and diffusion of ions," said Dominique Durand, professor of biomedical engineering at Case Western Reserve and the study's senior author. "But this shows a new mechanism. Neurons talk to each other cell to cell using electrical fields, propagating a wave of activity."

Durand worked with graduate students from Case Western Reserve's Neural Engineering Center: Mingming Zhang, Chen Qiu, Rajat J. Shrivacharan and Thomas P. Ladas; and Senior Research Associate Luis E. Gonzales-Reyes to investigate how epileptic seizure activity starts and spreads in the brain.

They inserted a 64-channel microelectrode array in the unfolded hippocampus of a mouse model to monitor its activity. They then injected the hippocampus, which is known to be involved in the most common form of epilepsy, with a drug to make the hippocampus epileptic.

They blocked chemical synapses from transmitting signals between neurons by reducing the calcium ion concentration below the level typically involved in signaling. They then blocked what are called "gap junctions," which electrically transmit signals across synapses, by injecting the antimalarial drug mefloquine, known to hamper the process.

Their tests showed that epileptic activity continued to spread at a speed of about 0.1 meter per second with or without synaptic transmission.

The propagation speed eliminated the third known route of epileptic propagation -- signaling by diffusion of sodium and potassium ions across brain cell membranes. Diffusion is too slow to be the method of transmission.

The researchers were left with the fourth known way that neurons communicate: electrical fields. When a group of cells fire together, they can generate currents and electric fields that can be large enough to excite their neighbors.

Computer simulations with a large set of neurons confirmed that a weak electrical field could, by itself, spread epileptic signals at the speed that matched their experimental results. The computer model also predicted that signal transmission would change speeds depending on the distance between neurons.

The researchers verified the prediction by injecting drugs that would either expand or decrease the space between cells. The closer the cells, the faster the transmission. The more distant the cells, the slower the transmission until -- at a certain distance -- the signal failed to propagate.

For some time, doctors have used diuretics to treat some types of epilepsy.Diuretics are known remove water from cells and but their anticonvulsant properties are not known, Durand said.

As water is removed from cells and enters the extracellular space, it increases the space between cells and may be pushing them beyond the reach of the weak electrical field, he said.

The researchers say that this finding does not diminish the importance of synaptic transmission in epilepsy but points to another synchronizing and propagation mechanism.

But "this discovery has implications for epilepsy," Durand said. "If cells in an excited state can talk to or influence each other, they can synchronize to a seizure-like state, propagate to neighbors thereby generating a full-blown seizure."

The electrical fields and the process of synchronization and propagation may be new targets for medicines or other treatments to prevent or limit seizures.

The researchers are now investigating a way to directly test the effect of electric field on seizure generation and propagation.


Story Source:

The above story is based on materials provided by Case Western Reserve University. Note: Materials may be edited for content and length.


Journal Reference:

  1. M. Zhang, T. P. Ladas, C. Qiu, R. S. Shivacharan, L. E. Gonzalez-Reyes, D. M. Durand. Propagation of Epileptiform Activity Can Be Independent of Synaptic Transmission, Gap Junctions, or Diffusion and Is Consistent with Electrical Field Transmission. Journal of Neuroscience, 2014; 34 (4): 1409 DOI: 10.1523/JNEUROSCI.3877-13.2014

Cite This Page:

Case Western Reserve University. "Researchers find epileptic activity spreads in new way." ScienceDaily. ScienceDaily, 24 January 2014. <www.sciencedaily.com/releases/2014/01/140124093704.htm>.
Case Western Reserve University. (2014, January 24). Researchers find epileptic activity spreads in new way. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2014/01/140124093704.htm
Case Western Reserve University. "Researchers find epileptic activity spreads in new way." ScienceDaily. www.sciencedaily.com/releases/2014/01/140124093704.htm (accessed April 23, 2014).

Share This



More Health & Medicine News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Big Pharma Braces for M&A Wave

Big Pharma Braces for M&A Wave

Reuters - Business Video Online (Apr. 22, 2014) Big pharma on the move as Novartis boss, Joe Jimenez, tells Reuters about plans to transform his company via an asset exchange with GSK, and Astra Zeneca shares surge on speculation that Pfizer is looking for a takeover. Joanna Partridge reports. Video provided by Reuters
Powered by NewsLook.com
Study Says Most Crime Not Linked To Mental Illness

Study Says Most Crime Not Linked To Mental Illness

Newsy (Apr. 22, 2014) A new study finds most crimes committed by people with mental illness are not caused by symptoms of their illness or disorder. Video provided by Newsy
Powered by NewsLook.com
Hagel Gets Preview of New High-Tech Projects

Hagel Gets Preview of New High-Tech Projects

AP (Apr. 22, 2014) Defense Secretary Chuck Hagel is given hands-on demonstrations Tuesday of some of the newest research from DARPA _ the military's Defense Advanced Research Projects Agency program. (April 22) Video provided by AP
Powered by NewsLook.com
How Smaller Plates And Cutlery Could Make You Feel Fuller

How Smaller Plates And Cutlery Could Make You Feel Fuller

Newsy (Apr. 22, 2014) NBC's "Today" conducted an experiment to see if changing the size of plates and utensils affects the amount individuals eat. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins