Scientists’ discovery that rodents, bats and nonhuman primates have a system in the brain for what amounts to dead reckoning navigation is one of the most important brain research developments of the past few decades.

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.

J oshua 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.”