The electrical activity of a few thousand neurons in the human brain correlates with thinking about math or quantity-related ideas, say researchers. The findings suggest how research that connects types of thoughts to brain activity could someday enable patients who are unable to speak to communicate with others.

Josef Parvizi, a neurologist at Stanford School of Medicine, and his team used brain implants in three patients to record the activity of a collection of neurons suspected to be involved in mathematical thinking. The patients were undergoing brain monitoring to help treat their epileptic seizures and had electrodes implanted on the surface of their brain so neuron activity could be monitored over several days.

The Stanford team compared videorecordings of the patients’ behaviors to the patterns of activity of a brain region suspected to be important for mathematical calculations. By recording from an implant, the researchers could observe more natural behaviors in patients than had been possible in previous studies.

Whenever the patients would consider math problems or even just quantitative thoughts—ideas such as “more than” or “smaller than”—the neurons were active, the researchers reported on Tuesday in Nature Communications.

Parvizi says his group has also recorded from other regions of the brain while monitoring patient behavior, but those results await publication. While researchers are far from able to read minds, the implant technique could be a good way to try to grasp what is going on inside a person’s head, says Parvizi. “This is just the beginning of a new era in brain research.”