Cellular-Level View of Electro-Stimulated Brain Obtained

For decades, doctors and researchers have used electricity to study or treat the human brain. Such investigations have led to the discovery of important centers in the cortex, such as the motor center and the pleasure one. Some treatments for conditions such as Parkinson's and even depression have been developed from electro-stimulation, but scientists have always lacked a thorough understanding of precisely why this type of therapy works. Now, a team finally manages to observe cellular-level interactions inside the brain, when it is stimulated with electricity, ScienceDaily reports.

The innovation, which was achieved by a Harvard Medical School (HMS) team of experts led by Neurobiology Professor Clay Reid, was made possible by the use of an optical imaging technology known as two-photon microscopy (TPM). This allowed the researchers to circumvent the greatest problems associated with measuring the neurons' electrical signals. In previous studies, it became obvious that identifying the weak electrical current generated by the neurons themselves was extremely difficult when high-voltage currents were applied onto the brain.

But TPM seems to have helped the Harvard science team surpass this obstacle. “When you are stimulating electrically you are using relatively high voltages, and those high voltages make it almost impossible to record the very small currents that neurons produce,” HMS postdoctoral fellow Mark Histed, also the first author of a new study detailing the finds, published in the August 27th issue of the scientific journal Neuron, shares.

“One prior theory was that at low currents, the neurons in a tiny ball around the electrode would activate, and if you increased the current, a larger ball would activate, but you would still only activate cells within that ball. What we showed was that, even at the lowest currents, you have cells very far away that are activated, so it's not just a tiny ball around the electrode tip that increases in size, but instead a very large, sparse pattern that fills in as the current is increased,” Histed explains the new results. TPM has shown that neurons across the brain activate when current is applied.

The team believes that the new conclusions will help experts create new types of neural prostheses in the future, such as the one currently being used to cure deafness and movement disorders. The new research was supported with funds from the national Institutes of Health (NIH) and Microsoft Research.