Electrical stimulation of neurons activates a widely distributed set of neurons (via axons), not just those being stimulated, Harvard Medical School neurobiologists have found, using optical imaging of mice neurons.

They used sensitive two-photon microscopy to track light emitted by a chemical triggered by increased calcium levels (which spike when a neuron fires) in the neurons as they were being exposed to electrical stimulation.

The researchers hope the technique will be important in understanding, rationalizing, and designing neural prostheses.