Motor Brain-Computer Interface Reanimates Paralyzed Hand

Over five million people in the United States live with paralysis (Armour et al., 2016), representing a large portion of the US population. Though the extent of paralysis varies from person-to-person, most with paralysis experience unmet needs that subtract from their overall life satisfaction. A survey of those with paralysis revealed “peer support, support for family caregivers, [and] sports activities” as domains where individuals with paralysis experienced less fulfillment—with lower household income predicting a higher likelihood of unmet needs (Trezzini et al., 2019). Consequently, individuals with sufficient motor function have turned to video games as a means to meet some of these needs, as video games are sources of recreation, artistic expression, social connectedness, and enablement (Cairns et al., 2019). Oftentimes, however, these individuals are limited by what games they are able to engage with—as they often “avoid multiplayer games with able-bodied players” (Willsey et al., 2025). Thus, Willsey and colleagues (2025) explore brain-computer interfaces as a valuable potential solution for restoring more sophisticated motor control of not just video games, but of digital interfaces used for social networking or remote work.

Brain-computer interfaces (BCIs) are devices that read and analyze brain activity in order to produce commands that are then relayed to output devices, with the intent of restoring useful bodily function (Shih et al., 2012). Willsey et al. explain how current motor BCIs are unable to distinguish between the brain activity corresponding to the movement of different fingers, so BCIs have instead relied on detecting the more general movement of grasping a hand (where the fingers are treated as one group). This limits BCIs to controlling fewer dimensions of an instrument: just being able to control a computer’s point-and-click cursor control as compared to typing on a computer. Hence, Willsey et al. seek to expand BCIs to allow for greater object manipulation—implementing finger decoding that will differentiate the brain output signals for different fingers, allowing for “typing, playing a musical instrument or manipulating a multieffector digital interface such as a video game controller.” Improving BCIs would also involve continuous finger decoding, as finger decoding has mostly been done retrospectively, where finger signals are not classified and read until after the brain data is analyzed. 

Willsey et al. developed a BCI system that is capable of decoding three independent finger groups (with the thumb decoded into two dimensions), allowing for four total dimensions of control. By training on the participant’s brain over nine days as they attempt to move individual fingers, the BCI can learn to distinguish brain regions that correspond to finger movements. These four dimensions of control are well reflected in a quadcopter simulation, where a patient with an implemented BCI is able to manipulate a virtual hand to fly a quadcopter drone through various hoops of an obstacle course. Many applications, even beyond video games, are apparent. These finger controls can be extended to a robotic hand or could reanimate the paralyzed limb. 

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The patient’s feelings of social connectedness, enablement and recreation were greatly improved. Willsey et al. note how the patient often looked forward to the quadcopter sessions, frequently “[asking] when the next quadcopter session was.” Not only did the patient find enjoyment in controlling the quadcopter, but they found training not to be tedious and the controls intuitive. To date, this finger BCI proves to be the most capable kind of motor BCI, and will serve as a valuable model for non-motor BCIs, like Brain2Char, a system for decoding text from brain recordings.

However, BCIs raise significant ethical considerations that must be addressed alongside their development. Are users responsible for all outputs from a BCI, even with outputs unintended? Given that BCIs decode brain signaling and train on data from a very controlled setting, there is always the potential for natural “noise” that may upset a delicate BCI model. Ideally, BCIs are trained on a participant’s brain in a variety of different circumstances to mitigate these errors. Furthermore, BCIs may further stigmatize motor disabilities by encouraging individuals toward restoring “normal” abilities. I am particularly concerned about the cost of this technology. As with most new clinical technologies, implementation is expensive and ends up pricing out individuals with lower socioeconomic statuses. These are often the individuals that face the greatest need for technologies like BCI. As mentioned earlier, lower household income predicts more unmet needs for individuals with paralysis. Nonetheless, so long as they are developed responsibly and efforts are made to ensure their affordability, there is great promise in motor BCIs.

 

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