Before any actual or imagined movement begins, signals arise in the brain’s cortex. When real movement occurs, the signal tends to originate in the hemisphere opposite the hand used; during imagined movement, the signal lacks a clear hemispheric origin. This distinction emerged from a study conducted by scientists from the Skolkovo Institute of Science and Technology. It highlights how the brain prepares for action even before muscles respond, tying into the protective layers that cover the brain and spine, known as the meninges, which help cushion neural activity.
Before reaching for a pen or raising a glass, the brain constructs a full representation of the intended action. Visuomotor transformations convert sensory input into precise motor commands, ensuring accurate execution. Yet it is possible to imagine moving without any muscular activation. In such cases, visual information still engages the motor areas of the brain, but the initiation of the actual response is halted somewhere in the processing stream, leaving mental effort without a subsequent muscular outcome.
In the described experiment, 17 volunteers participated, with an average age around 23. They placed their hands on a two-button panel that illuminated intermittently. When a button lit, subjects were instructed to press it or to imagine pressing it. Throughout the task, researchers recorded the participants’ electroencephalograms to monitor brain activity in real time.
Illumination of the button triggered signals in the motor cortex during both real and imagined actions. However, during genuine movement, these signals predominantly appeared in one hemisphere: pressing with the right hand produced activity mainly in the left hemisphere, and pressing with the left hand produced activity mainly in the right hemisphere. The duration of these signals extended when reaction times increased, such as when participants delayed pressing after the light appeared. This correlation between reaction timing and motor cortex activation underscores how timing and intention shape neural engagement during action planning and execution.
The findings suggest that the brain constructs a mental image of movement differently for actual versus imagined actions. Such insights have implications for stroke rehabilitation, where motor pathways may be disrupted. The researchers propose that motor-cortex signals could serve as a sensitive marker for monitoring recovery in stroke patients, potentially revealing progress before observable movements occur. Nikolai Syrov, a senior researcher at Skoltech and a participant in the study, noted that tracking these cortical signals could offer a window into the brain’s evolving motor systems, providing a gauge of rehabilitation progress long before functional improvements become evident [Citation: Skoltech research team].
In discussions of cognitive health, considerations about medication and diagnostic tests remain important. It has been noted in prior work that certain medications can sometimes produce false-positive results in assessments for Alzheimer’s disease, highlighting the need for careful interpretation of imaging and electrophysiological data in clinical contexts [Citation: prior clinical literature].