Whenever we see, hear, or otherwise perceive the world, thousands of sensory neurons send signals to our spinal cord and brain. Because neurons are miniscule pieces in a giant system, their power lies in their ability to communicate with other neurons. When neurons communicate frequently, the synapses between them get stronger, making it easier to send future signals. We refer to the brain’s fundamental ability to change as “neuroplasticity.”Humans have most of our neurons from birth. And because neurons communicate through electrical signals, we can directly alter brain circuits with electrical stimulation.