This newly discovered mechanism could help us better understand memory, epilepsy, and healthy physiology.
For a quick lesson in basic neuroscience, it’s been long known that the neural signals in our brains are sent via mechanisms like synaptic transmissions, gap junctions, and diffusion processes. Now, a new study finds that there’s another way our brains transmit information from place to place: electrical fields.
Scientists have recorded neural spikes in the brain that travel at speeds too slow to be explained by any of the other signaling mechanisms. Researchers couldn’t think of any other plausible explanation for these slow-travelling neural spikes other than them being transmitted by a mild electrical field, and now they’ve been able to detect these electrical fields in mice.
"Researchers have thought that the brain's endogenous electrical fields are too weak to propagate wave transmission," Dominique Durand, a biomedical engineer at Case Western Reserve University, said in a press release. "But it appears the brain may be using the fields to communicate without synaptic transmissions, gap junctions or diffusion."
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Before running tests on mice, the researchers used computer simulations to model their hypothesis. They found that electrical fields begin in one cell or group of cells, but then mediate propagation (multiplication of organisms) across layers of neurons. These electrical fields have low amplitudes (approximately 2 to 6 mV/mm) but are able to excite and activate immediate neighbors. This sparks an “excite-and activate-neighbors” cycle, and it spreads across the brain at a rate of about 0.1 meters (4 inches) per second.
The scientists tested this out on mouse hippocampi, the central part of the brain associated with memory and spatial navigation. The research produced similar results to the computer modeling, and the scientists also observed that the speed of the wave slowed down when they applied a blocking field.
"The implications are that such directed fields can be used to modulate both pathological activities, such as seizures, and to interact with cognitive rhythms that help regulate a variety of processes in the brain," said Steven J. Schiff, director of the Center for Neural Engineering at Penn State University, who was not involved in the study.
In the study, the researchers write that this novel mechanism could be involved in other types of propagating neural signals as well, like slow-wave sleep, theta waves, hippocampal waves, or seizures.
Since these waves are associated with things like memory, epilepsy, and health physiology, hopefully these findings will be further studied in order to help us better understand them.
The research is published in the Journal of Neuroscience.