Mirror Neurons in the Brain: Mechanisms of Joint Action and Empathy

Neurophysiologist Giacomo Rizzolatti is considered one of the world’s leading experts on the so-called mirror neurons in the human brain. These neurons play a special role not only in the execution of simple imitative motor acts but also in social cognition and human behavior. Together with philosopher Corrado Sinigaglia, he wrote a book demonstrating how strong and enduring the bonds are that connect us to others—or, in other words, how misguided it would be to try to understand the “I” without the “We.”

Some time ago, the renowned theater director Peter Brook remarked in an interview that with the discovery of mirror neurons, neuroscience finally took a step toward understanding what people in theater have long known: all the efforts of an actor would be in vain if he could not overcome all linguistic and cultural barriers and share his sounds and movements with the audience. The audience, in turn, becomes an active participant in the event, contributing to it. This participation is the essence of theater and its development, and mirror neurons—which are activated both when we perform an action and when we merely observe it—provide a biological explanation for this shared experience.

Brook’s mention of mirror neurons is evidence of the enormous interest their unexpected properties have sparked beyond physiology. Artists, psychologists, educators, sociologists, and anthropologists have been captivated by mirror neurons. However, few people know the story of their discovery, the experimental research and theoretical assumptions that made it possible, or the profound implications this discovery has for our understanding of the brain’s architecture and function.

Everyday Gestures and the Motor System

Let’s start by analyzing everyday gestures—like reaching for an object, picking it up, or bringing food to our mouth. We tend to underestimate the importance of these gestures simply because they are so familiar. For many years, neuroscience (along with other disciplines) considered the motor system, which plays a leading role in these gestures, to be of secondary importance.

For any action, from basic acts like grasping to more complex ones requiring special skills—such as playing a piano sonata or performing specific dance moves—mirror neurons allow our brain to match the action we observe with the action we can perform, helping us determine its meaning.

For decades, it was believed that the motor areas of the cerebral cortex were responsible for nothing more than executive functions, with no perceptual or cognitive value. This made it difficult to explain our motor behavior, especially when it came to analyzing the vast array of sensory information and identifying the neural substrate of cognitive processes related to intentions, beliefs, and desires. Once it was established that the brain can select incoming information and link it to mental representations generated more or less automatically within itself, the study of movement was reduced to the mechanisms of its execution—following the classic scheme: perception → cognition → movement.

This scheme sufficed as long as simplified views of the motor system prevailed. But today, we know that this system is not only a mosaic of frontal and parietal cortical areas closely connected to visual, auditory, and tactile regions, but it also possesses much more complex functional properties than previously thought.

The Discovery of Mirror Neurons

It was discovered that certain areas of the cortex contain neurons that are activated in response to goal-directed motor acts (like grasping, holding, or manipulating objects), but not in response to simple movements. Moreover, these neurons respond selectively to objects of different shapes and sizes, both when we interact with these objects and when we merely observe them. Apparently, these neurons can classify incoming sensory information based on the range of potentially available actions, regardless of whether those actions will actually be performed.

When we examine how the brain works, it becomes clear how abstract our traditional explanations of behavior are, as we habitually separate intentional actions from the simple physical movements needed to carry them out. In truth, these explanations are as abstract as many experiments that record neuronal activity in animals—like monkeys—treated as little robots programmed to perform specific tasks. However, when neuronal activity is recorded in the context of natural behavior, where the animal can choose whether or not to take food or objects offered to it, it becomes clear that at the cortical level, the motor system is responsible not for individual movements, but for actions. The same is true for humans: we rarely move our hands or lips without a purpose; usually, there is an object we want to reach, grab, or taste.

These actions, as long as they are goal-directed and not just movements, form the basis of our impressions of the environment and give objects immediate meaning. The strict separation of perceptual, cognitive, and motor processes is largely artificial: perception appears to be embedded in the dynamics of action, making it a much more complex process than previously thought. Moreover, the acting brain is also (and primarily) an understanding brain. This is a pragmatic, pre-conceptual, and pre-linguistic form of understanding, but it is no less significant, as it underlies many of our celebrated cognitive abilities.

Understanding Through Mirror Neurons

This type of understanding is reflected in the activation of mirror neurons. Discovered in the early 1990s, they answer the question of how and why recognizing the actions and even intentions of others relies primarily on our own behavioral repertoire. For any action, from basic acts like grasping to more complex ones requiring special skills—such as playing a piano sonata or performing specific dance moves—mirror neurons allow our brain to match the action we observe with the action we can perform, helping us determine its meaning. Without such a mirror mechanism, we would have a sensory representation—a “visual” description—of others’ behavior, but we would not know what they are actually doing. Of course, we could use our higher-level cognitive abilities to think about what we saw and infer the intentions, expectations, and motivations of others, giving their actions meaning. But in reality, our brain can extract this meaning directly, based solely on our motor abilities and without any reasoning.

This suggests that the mirror neuron system is essential for the emergence of shared experiences, allowing each of us to act not only as individuals but also as members of society. Various forms of imitation—both simple and complex—as well as learning, verbal and gestural communication, all involve the activation of specific mirror neuron systems. Furthermore, our ability to understand the emotional reactions of others is also linked to brain regions with mirror properties. We share emotions with those around us as directly as we share actions: perceiving pain, grief, or disgust experienced by another person activates the same areas of the cerebral cortex as when we experience these emotions ourselves.

The Social Bonds Created by Mirror Neurons

All of this shows how strong and enduring the bonds are that connect us to others—or, in other words, how misguided it would be to try to understand the “I” without the “We.” As Peter Brook reminded us, actors on stage must break through all linguistic and cultural barriers; otherwise, they cannot share their actions and experiences with the audience. The study of mirror neurons, it seems, for the first time in history provides us with a unified experimental and theoretical framework to unravel the mystery of this shared experience created by theater, which, in essence, underlies our everyday lives.