Earlier peer reviewers had difficulty with CES studies, because it was so new that few had heard about it.Some reviewed CES studies under the impression that they were studies using electroshock treatment. Others assumed that the small electrical current provided in CES stimulation could not effectively enter the brain, while yet others decided that even if by chance it could find its way past the cranium, the amount of stimulus was too small to have an effect on neurons in the brain.
Researchers over the years have found that the electric current from CES stimulation goes through every part of the brain. One of these researchers was a doctoral candidate studying the possibility of combining CES and biofeedback simultaneously, measuring the electroencephalograph ( EEG) in the process (Shroeder, 1999). A second, a doctoral candidate using low resolution brain electromagnetic tomography (LORETA) imaging, found that CES induced changes in every one of 2,394 gray matter voxels measured (Kennerly, 2006).A study at the University of Wisconsin found that CES stimulated the emptying of presynaptic vesicles in the rabbit brain, then generated an increased number of vesicles in the presynaptic neuron as stimulation continued. These returned to a normal level following cessation of stimulation.These changes were mea¬ sured by implanted devices placed in numerous areas of the brain, covering the majority of the cortex (Siegesmu nd, Sances, & Larson, 1967).
To learn the mechanism in which changes had been wrought in depression and anxiety scores, researchers began to measure neurotransmitter levels prior to and following CES treatment.Pozos, Strack, White, and Richardson (1971), at the University of Tennessee Medical School, deliberately Parkinsonized canine subjects by chemically altering their adrenergic/cholinergic balance. He then discovered that either L-dopa or CES could similarly bring the subjects back to a normal, non-Parkinsonian state in a few hours, while subjects put on normal rations of food and water required several days to return to a normal state.CES, he inferred from his results, acts as a rebalancing force in organisms whose normal neurotransmitter system is out of balance.