Srini Pillay, an assistant clinical professor of psychiatry at Harvard Medical School and author of Life Unlocked: 7 Revolutionary Lessons to Overcome Fear, responds:

Visualization and action are intimately connected, involving the motor cortex. Thinking about our body doing something—raising an arm or walking forward—activates the motor cortex directly.

Imagining allows us to remember and mentally rehearse our intended movements. In fact, visualizing movement changes how our brain networks are organized, creating more connections among different regions. It stimulates brain regions involved in rehearsal of movement, such as the putamen located in the forebrain, priming the brain and body for action so that we move more effectively. Even picturing others in motion warms up the “action brain” and helps us figure out what we want to do and how we can coordinate our actions with those around us. Over time the brain learns our routine movements, allowing these actions to become more automatic and fine-tuned.

Some people ask, “If my movement brain is activated, why don't I just move?” You do—but not right away. Initially when you imagine moving, your brain signals the motor cortex below the threshold necessary to prompt physical activity. Several factors affect whether this signaling is great enough to spark action.

Perspective is also important. When we visualize ourselves in the first person, for instance, we see only what is around us. But when we imagine ourselves in the third person, we can envision more specifically what our body is doing in a situation. Some studies show that imagining in the first person may activate muscles more powerfully than when we picture ourselves in the third person. It is also important for the action we imagine to be consistent and believable.

Overall, this ability to trigger the motor cortex by imagining an action offers great promise in therapies for patients recovering from stroke and for athletes or dancers working to develop expertise in their craft. But as we get older, the motor cortex has to work harder to imagine actions, so exercising our visualization skills remains important throughout our lives. Mirror neurons, located in different regions of the brain but especially the brain's motor system, may also play a role in generating movement. Studies have shown that the same brain regions become active when a person performs a task and when a person observes someone carrying out a task. But mirror neurons may have an even more complex part than aping others' movements; these neurons may help explain our capacity for empathy.