Neuroprosthetics: The Bridge Between People and Technology

Neuroprosthetics comprises a field that is rapidly expanding due to advancements in various fields, particularly neuroscience, computer science, bioengineering, and medicine. Neuroprostheses, in short, are artificial devices that can directly interact with a person’s neuromuscular system. They include a range of devices such as vestibular implants to restore balance, spinal cord stimulators to treat chronic pain, or even fully functional limbs. Neuroprostheses are an incredibly interdisciplinary field, involving neurosurgeons, biomedical engineers, neuroscientists, and large biotechnology companies. Neuroprosthetics have the potential to greatly improve the quality of life of people who may need one and offer an opportunity for integration between the human body and technology. Despite this, though, neuroprostheses remain relatively novel and are often used as a last resort for medical treatment when pharmaceutical treatments fail, according to the AMA Journal of Ethics.

Neuroprosthetics differ from traditional prosthetics in a multitude of ways including their purpose and function. Prosthetics are artificial body parts that replace a non-functional or absent body part. This can include limbs, joint replacements, heart valve replacements, and intraocular lenses. Prosthetics are used to treat a variety of conditions and aid individuals who suffer from: traumatic injuries requiring reconstructive surgery, congenital (birth) deformities, gradual bodily degradation (aging), and chronic diseases. Neuroprosthetics are artificial devices that deliver and/or record electrical signals from the neuromuscular system to replace and improve impaired nervous system function and quality of life in patients. Common kinds of neuroprosthetics include technologies such as pacemakers, cochlear and retinal implants, and limbs. Both prosthetics and neuroprosthetics aim to restore, replace, and/or enhance lost bodily functions (i.e., movement) caused by injury or disease. Neuroprosthetics additionally enhance motor skills, sensory perception, and cognition and memory, which traditional prosthetics cannot do. That being said, the most notable difference between neuroprostheses and traditional prostheses is that neuroprostheses can directly interface with the neuromuscular system to augment and even replace neural function. In short, neuroprosthetics incorporate digital technology with the human body while traditional prosthetics do not.

Neuroprosthetics interface with the neuromuscular system by taking in or outputting electrical signals in the form of neural oscillations. Neural oscillations are the rhythmic and collective synchronization of neurons firing, which promote sensory, motor, and cognitive function of the nervous system (Nature).  In a healthy individual, this process is unaffected and functions without error, but due to degenerative or psychiatric disorders such as stroke, spinal cord injuries, or traumatic brain injuries, this process can be disrupted. Despite advancements in medicine and pharmaceutical treatments, these conditions are not always easily treated with medication or therapies and require another mode of treatment. Neuroprosthetics are now increasingly being used as an alternative to pharmaceutical treatments or when pharmaceutical treatments fail.

There are a variety of neuroprostheses used to treat a multitude of conditions, though they generally fall into four broader categories: motor neuroprostheses, sensory neuroprostheses, cognitive neuroprostheses, and bidirectional neuroprostheses. Motor neuroprostheses restore lost motor function through electrical stimulation of structures involved in movement, including muscles, peripheral nerves, the spinal cord, or the brain. They can serve multiple purposes and can be used to build up muscle strength, as assistive technology, or for fine-motor control. Motor neuroprostheses include prosthetic limbs or fully implanted electrodes throughout the neuromuscular system or spinal cord and can be controlled by intracranial electrodes. Ultimately, motor neuroprostheses allow people to regain muscle strength, aid with speech, operate prosthetics with fine-motor control, or operate computer cursors and software. This is useful for treating patients who suffer from hemiplegia, paralysis affecting one side of the body caused by stroke, and spinal cord injuries. On the other hand, sensory neuroprostheses are used to restore sensory organs, namely hearing, sight, and touch, and include technologies such as cochlear implants, retinal implants, or even limb neuroprosthetics, which can sense stimuli. Somatosensory neuroprostheses give sensory feedback and improve cognitive integration for amputees who wear a mechanical prosthetic. This is accomplished by improving the embodiment of said prosthetic, reducing phantom limb perceptions in amputees, and decreasing the weight perception of prostheses. Peripheral somatosensory neuroprosthetics (peripheral somatosensation referring to tactile, thermal, and pain stimuli) can generate more natural sensations, including touch, pressure, and proprioception (spatial awareness of the body) in prosthetics. Furthermore, sensory neuroprostheses are crucial for children as they allow for proper brain maturation, for example, essential language development in inborn deafness. Moreover, there are also cognitive and memory neuroprostheses that process neuronal signals and utilize decoding algorithms to restore decision-making, attention, and working memory. Decoding algorithms are mathematical mappings of brain activity that extract cognitive information and are used in motor neuroprostheses, but are now being applied to cognitive and memory neuroprostheses (ScienceDirect) . Cognitive and memory neuroprostheses have been used for the treatment of neurodegenerative diseases, namely Alzheimer’s and Parkinson’s Disease as well as epilepsy, though they remain novel. Finally, there are bidirectional neuroprostheses that both record and stimulate the nervous and neuromuscular system to communicate sensory, motor, and cognitive signalling. All of the aforementioned neuroprostheses, motor, sensory, and cognitive and memory, are capable of bidirectional functionality. Bidirectional functionality refers to the neuroprosthetic’s ability to record an input from the neuromuscular system and to stimulate the neuromuscular system, hence the ‘two’ directions. In addition, bidirectional neuroprosthetics represent the clearest hybridization between the human body and technology as they not only receive inputs from the body but also provide outputs. 

Neuroprosthetics, beyond treating diseases and aiding those with disabilities, offer a huge improvement to the quality of life of patients. Those with spinal cord injuries face daily challenges, particularly difficulty with essential transfers (i.e. wheelchair to bed, car, etc.) and accessing elevated items not within reach of a wheelchair. Neuroprostheses grant individuals greater independence and the ability to facilitate difficult tasks or ones thought to be previously impossible from a wheelchair. Patients also have fewer or less severe symptoms related to secondary conditions associated with spinal cord injuries including UTIs, pressure sores, and osteoporosis. Beyond physically aiding patients, neuroprostheses enable individuals with significant incurable impairments to improve self-perception of their health, a key component to improving quality of life. Patients report that, with neuroprosthetics, they are able to stand for greater amounts of time, interact with others in standing positions, feel less disabled, and socialize with others more “normally” (NIH). All of these improve both physical and mental health, with improvement in one creating progress in the other. 

Overall, neuroprostheses’ ability to be interfaced with the neuromuscular system demonstrates integration between technology and the human body. Ethically, there are many concerns regarding neuroprostheses, including the distinction between treatment and human identity enhancement (alter or improve beyond typical human limits). Much of the conspiracy surrounding the development and use of neuroprostheses is driven by a lack of knowledge surrounding neuroprostheses, as well as the idea that the human body and technology are becoming intertwined. Additionally, the idea that we use technology to remedy human health issues only furthers the narrative that people are becoming increasingly dependent on technology. Humans are now able to physically connect their bodies to technology interfaced with their own nervous systems for aid with daily activities. It is undeniable that neuroprosthetics represent a shift in society from one mentally dependent on society to one now mentally and physically dependent on society. Society uses technology for instant information retrieval, offloading both cognitive tasks and memory retrieval, and now the most vulnerable members of society are physically dependent on technology. Regardless of this dilemma, though, neuroprosthetics have the potential to positively impact people who suffer from a wide range of debilitating conditions, particularly birth defects, amputations, and neurological diseases. Moving forward, neuroprosthetics will continue to be manufactured and used because of their life-changing capabilities.