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Columbia University scientists recently tested a new optical technique to study how information is transmitted in the brains of mice and made a surprising discovery: When stimulated electrically to release dopamine (a neurotransmitter or chemical released by neurons, or nerve cells, to send signals to other nerve cells), only about 20 percent of synapses — the connections between cells that control brain activity — were active at any given time.

The effect had never been noticed. “Older techniques only revealed what was going on in large groups of synapses,” explained David Sulzer, PhD, professor of neurobiology in Psychiatry, Neurology, and Pharmacology at Columbia University Medical Center (CUMC). “We needed a way to observe the neurotransmitter activity of individual synapses, to help us better understand their intricate behavior.”

Most biology students will be able to tell you that neural signals are sent via mechanisms such as synaptic transmission, gap junctions, and diffusion processes, but a new study suggests there’s another way that our brains transmit information from one place to another.

Researchers in the US have recorded neural spikes travelling too slowly in the brain to be explained by conventional signalling mechanisms. In the absence of other plausible explanations, the scientists believe these brain waves are being transmitted by a weak electrical field, and they’ve been able to detect one of these in mice.

“Researchers have thought that the brain’s endogenous electrical fields are too weak to propagate wave transmission,” said Dominique Durand, a biomedical engineer at Case Western Reserve University. “But it appears the brain may be using the fields to communicate without synaptic transmissions, gap junctions or diffusion.”