Electrical Stimulation Impacts How the Human Brain Learns

It turns out that scientists can artificially impact the learning process. By stimulating a certain population of neurons within the brain with electricity, researchers can alter learning.

"Stimulating the substantia nigra as participants received a reward led them to repeat the action that preceded the reward, suggesting that this brain region plays an important role in modulating action-based associative learning," said Michael Kahana, one of the researchers, in a news release.

The substantia nigra is a deep brain structure where dopamine-containing neurons are located. In this case, 11 participants underwent deep brain stimulation (DBS) as treatment for Parkinson's disease. During an awake portion of the treatment, the patients played a computer game where they chose between pairs of objects that carried different reward rates. The objects were displayed on a computer screen, and the participants made selections by pressing buttons on hand-held controllers. When they were given a reward, they were shown a green screen and heard the sound of a cash register. They had to figure out which ones were "good" options based on trial and error.

What was interesting, though, is what happened when stimulation was provided in the substantia nigra following a reward. The volunteers tended to repeat the button press that resulted in the reward; in fact, this was the case even when the rewarded object was no longer associated with that button press.

"While we've suspected, based on previous studies in animal models, that these dopaminergic neurons in the substantia nigra play an important role in reward learning, this is the first study to demonstrate in humans that electrical stimulation near these neurons can modify the learning process," said Gordon Baltuch, one of the researchers, in a news release. "This result also has possible clinical implications through modulating pathological reward-based learning, for conditions such as substance abuse or problem gambling, or enhancing the rehabilitation process in patients with neurological deficits."

The findings are published in the Journal of Neuroscience.