Scientists discover that the brain responds to others’ actions as if they were its own

When we watch someone move their finger, our brain doesn’t remain passive. Research conducted by scientists from HSE University and Lausanne University Hospital shows that observing movement activates the motor cortex as if we were performing the action ourselves—while simultaneously ‘silencing’ unnecessary muscles. The findings were published in Scientific Reports.

Motor resonance is a phenomenon in which observing another person’s movements triggers activity in the observer’s motor cortex, as though they themselves were moving. It is linked to the activity of mirror neurons—special brain cells that fire both when we perform an action and when we watch someone else do it. These neurons allow us to understand others’ actions and learn through imitation.

A new experiment by researchers from HSE’s Centre for Cognition & Decision Making and Lausanne University Hospital made it possible to pinpoint the stage of movement at which the motor response reaches its peak. Thirty people took part in the study. First, they were shown photographs of finger movements, then videos of these movements, and finally the last frame of the video clip.

When a person merely observes a movement, their brain may be active or not—and this is not outwardly visible. The muscles remain still, and no signals are recorded. A standard electrode would not detect anything in such a situation as there is no muscle activity.

To overcome this limitation, the researchers used transcranial magnetic stimulation (TMS). With this technique, they sent a signal to the brain, effectively ‘nudging’ the motor cortex to produce a measurable response. This allowed them to assess how ‘ready’ the brain was to act. If a person was deeply engaged in the observed movement, even a weak impulse could elicit a strong reaction in the relevant muscle. If the person was not engaged, the brain’s response would be weak or absent. In this way, TMS made it possible to literally ‘probe’ the brain’s readiness to initiate a movement it was only watching.

In the study, stimulation was applied at various time points: immediately after the movement began, and at 320 and 640 milliseconds after. Participants sat still, watching the screen, while the scientists recorded electrical activity from their hand muscles to see how actively the motor cortex was responding to the visual stimulus. The strongest muscle signal occurred not during the action in the video, but slightly afterward—when the movement had ended but was still fresh in memory.

In the case of viewing the final frame of the video (Postvideo), activity in the relevant muscle increased, while activity in a neighbouring, non-involved muscle was suppressed. This brain response mirrors the way it controls our own movements. In neurophysiology, this mechanism is known as surround motor inhibition—it ‘switches off’ unnecessary muscles to improve precision.

‘Our main discovery is that the brain engages the same inhibition mechanisms as in real movements, even when a person is merely observing an action. This indicates a high level of engagement with another’s movement—as if it were one’s own—at the brain–muscle connection level. It also helps us better understand the importance of motor resonance in perceiving movements,’ notes Matteo Feurra, one of the study’s authors and a leading research fellow at HSE’s Centre for Cognition & Decision Making.

The findings could be useful for neurorehabilitation, especially in restoring movement precision after injury or stroke. They also confirm the effectiveness of learning through observation, including in sports. Moreover, they offer new insight into how we ‘immerse’ ourselves in others’ actions—mechanisms that may underlie empathy itself.