The system is built on what are called grid cells, neurons that emit pulses of electricity in a regular pattern that maps the animal’s movement.
Scientists predicted they would find grid cells in humans, and now they have. Joshua Jacobs of Drexel University in Philadelphia and a team of scientists including Michael J. Kahana at the University of Pennsylvania and Dr. Itzhak Fried at U.C.L.A. and Tel-Aviv University, reported in Nature Neuroscience on Sunday that signals from electrodes implanted in human patients with severe epilepsy proved the presence of grid cells that function in the same way as those found in other mammals.
“It completes the picture,” said Edvard I. Moser of the Norwegian University of Science and Technology, one of the discoverers of grid cells. “It’s a significant contribution.”
Dr. Jacobs said the research was important to do because, although it had seemed likely that grid cells existed in human beings, it was far from certain.
“It’s not at all clear that humans and rodents behave in the same manner,” he said.
An area of the brain where grid cells are found in rats, and now in humans, the entorhinal cortex, is often damaged in the early stages of Alzheimer’s disease, so knowing how the navigation system works is important, Dr. Jacobs said. The scientists also located grid cells in another brain area in humans, the cingulate cortex, where, Dr. Jacobs said, they have not been found in rats.
The research involved the collaboration of neurosurgeons, research neuroscientists, and 14 patients with drug-resistant epilepsy, who had electrodes implanted in their brains to locate the source of the seizures before surgery. The patients volunteered to play a video game in which they navigated a virtual environment; analysis of brain cell activity recorded during the game-playing provided the data for analysis.
The same patterns characteristic of rodent grid cells were found in humans as they navigated, Dr. Jacobs said, showing that humans are using the “same neural mechanism.”
Gorman, James. 2013. “Navigational Cells Located in Human Brains”. The New York Times. Posted: August 4, 2013. Available online: http://www.nytimes.com/2013/08/06/science/navigational-cell-systems-located-in-human-brains.html?_r=0