Researchers have discovered that the activity in our brain differs when imagining movement compared to actually performing it. While both scenarios involve a preceding signal in the cerebral cortex, imaginary movement lacks a clear connection to a specific hemisphere. This understanding can potentially assist in medical practices such as developing neuro trainers and monitoring the restoration of neural networks in individuals recovering from strokes. The findings have been documented in the journal Cerebral Cortex.
Prior to physically executing an action, our brain constructs a complete perception of that movement. These visual-motor transformations are crucial for the precision of our motor functions. Knowledge about these mechanisms helps patients regain motor activity after experiencing a stroke. However, not all movements are carried out to completion. In some cases, visual information reaches the motor areas of the cortex responsible for movement, but the initiation of the reaction is hindered, preventing real muscle activation despite the mental effort exerted.
Currently, scientists are unaware of how brain activity preceding an actual movement differs from that which occurs before an imagined one. This is precisely what motivated the researchers to investigate further, as comprehension of our brain’s activity during movement can significantly improve motor rehabilitation techniques following a stroke.
To explore the distinctions in visual-motor transformations in real and imaginary movements, a team of scientists from Skoltech and Moscow State University conducted an experiment involving 17 volunteers with an average age of 23. The participants placed their hands on a panel equipped with two buttons that were intermittently illuminated. They were instructed to focus on only one of the buttons. When a button lit up, the volunteers had to either physically press it or imagine doing so, according to the researchers’ instructions. During the experiment, the scientists recorded the electroencephalogram (EEG) of the participants. The neuroscientists then analyzed the signals from the cortical regions associated with movement preparation and the occurrence of sensory sensations in the hands during movement.
Both real and imaginary movements elicited activity in the sensorimotor cortex in response to the button illumination. However, in the case of real movements, this activity was primarily observed in one hemisphere. The researchers propose that the presence of a preceding signal in the brain indicates the transformation of visual stimuli into movement. The strongest preceding signal was detected in the frontal-central regions of the hemisphere opposite to the actively engaged limb. For instance, when a person pressed the button with their right hand, the left hemisphere exhibited activation, and vice versa. Additionally, the duration of the preceding signal increased when the person’s reaction to the button’s light was slower or delayed.
Interestingly, the preceding signal associated with imaginary movement was not linked to a specific hemisphere of the brain. Arousal accumulated in various areas of the sensorimotor cortex prior to the movement, suggesting that the formation of a mental image during imagination and actual execution of an action occur through distinct mechanisms.
The researchers also investigated whether any signals emerged in the volunteers’ brains when a non-targeted button was illuminated. Surprisingly, in response to these non-targeted stimuli, the participants exhibited a preceding signal, albeit weaker and of shorter duration compared to the targeted stimuli.
The presence of such a non-target signal indicates that, during decision-making processes, the brain initially evaluates visual information before deciding to inhibit movement. Furthermore, it suggests that the motor areas of the cortex do not remain inactive during stimulus evaluation, and the presence of a preceding signal does not always lead to an immediate motor response.
A stroke disrupts the balance between inhibition and arousal in the cerebral cortex, as well as the interactions between hemispheres and the motor cortex with visual areas. The researchers propose utilizing cortical signals related to movement to assess the condition of brain networks responsible for converting visual signals into motor actions in stroke patients. These signals can also be used to evaluate the effectiveness of rehabilitation. This approach offers high sensitivity, as improvements in the state of the brain’s motor systems can be detected even before they manifest as physical movements, stated Nikolay Syrov, a senior research scientist at Skoltech and a participant in the study.
1. Source: Coherent Market Insights, Public sources, Desk research
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