We’ve all heard about prosthetic implants or seen them, maybe in real life or in movies or series, but are we aware of the field of Neuroprosthetics? Prosthetic implants are artificial devices to replace missing body parts that might have been damaged due to an accident or were absent since birth. These implants are called Prostheses (prosthesis as a singular) and the name comes from the Greek word “prostithenai” meaning ‘to add to, or to put in addition’; basically adding the artificially made body part to the natural body.

Prosthetics is the field of research in designing and building artificial limbs. Before the times of modern medicine, the survival rates for amputation patients and related diseases were low. However, archaeologists have uncovered artificial toes in Ancient Egypt dating back as early as 950 B.C.

Early prostheses were heavy and made of wood and leather, but today’s lighter materials of plastic, aluminium, and composite materials that provide amputees with function and mobility, are used in the field of prosthetics. These resemble the function of a biological limb more closely. The prosthetic limb can also be customized to individuals, offering a much more comfortable fit.

However, the light-weightness and comfort of prostheses are not the most advanced developments in the field. It is the field and the world of neuroprosthetics that has changed the medical world and aims to make the lives of people who need artificial limbs much easier and functional. Hearing the term ‘Neuroprosthetics’ we all can guess that it is something related to the brain or the nervous system, and now that you’ve read the definition of prosthetics, it must be making sense that it’s nothing but the making of artificial limbs that have some connection to the brain in the field of biomedicine. Technically speaking, neuroprosthetics refers to the field of research in controlling artificial limbs and other devices using the human brain, and in many cases, allowing the device to send signals back to the brain.

The working of Neuroprosthetics is based on the cells called neurons in our brain. The neurons are different from the other cells of the body; they send information via electrical signals, which travel quickly through large networks of neurons to coordinate various brain functions. In the prostheses, electrodes can be used to deliver electrical current to neurons, and neurons will respond to that current similar to how they respond to a signal from another cell. Thus, the biomedical devices can be created as an alternative to a body part if electric signals sent by the cells can be replicated artificially. They basically enhance the input or output of a neural system. Neural prostheses are a series of devices that can be used as substitutes to the motor, sensory, or cognitive modality that might have been damaged as a result of an accident, trauma injury, disease, or were present by birth. Up until now, neuroprosthetics for hearing and sight have been developed based on how auditory and visual neurons work.

One of the oldest forms of neuro-prosthetic implants is the cochlear implant. It is a small and complex electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. It has an external portion that sits behind the ear and another part that needs to be surgically placed under the skin. It cannot restore normal hearing. Instead, it gives a deaf person a useful representation of sounds in the environment and helps him or her to understand speech. However, a cochlear implant is different from a hearing aid. A hearing aid amplifies sounds so it can be detected by disabled ears. On the other hand, cochlear implants bypass damaged portions of the ear and they directly stimulate the auditory nerve. Signals generated by this implant are sent through the auditory nerve to the brain, which recognizes these signals as sound.

One of the advancements in neuroprosthetics is a prosthetic for vision – the first artificial retina (visual prosthetics/retina implant). The artificial retina works somewhat like the cochlear implant, but this device uses a small camera that is attached to a pair of glasses to pick images, which the device’s processor converts into pixels (light and dark). Then the device’s receiver turns this information into electrical signals. These signals are sent to a sheet of photoreceptor-stimulating electrodes that are on the retina. Lastly, the photoreceptors send this information to the optic nerve and to the brain.

One of the most exciting innovations in the Neuro-prosthetics world has been the emergence of BMI – Brain-Machine Interfaces. BMI has the potential to provide natural and complex upper extremity control which depends upon volitional signals recorded from brain regions that are used for movement control. However, the current state of the science is in flux from the basic to the clinical domain, and due to this, there are a number of issues that will need to be considered and worked upon to make it possible for BMI to work.

Currently, neuro-prosthetics has been able to create implants for the application in the following category of disorders:

Motor Neuron Disorders –  epilepsy and Parkinson’s disease

Physiological Disorders – kidney diseases, Auditory Processing disorders,  cardiovascular disorders, ophthalmic disorders

Cognitive Disorders: severe depression and alzheimer’s disease

The neuro-prosthetics market was valued at 5.84 billion US Dollars in the year 2017 and is expected to grow at the rate of CAGR 12.4% to the amount of 10.48 billion US Dollars by 2022. The implants are priced high as the amount of research and technology that goes behind it is intense, but there is a continuous trial to make it more accessible to people. The demand for these is very high as there are multiple cases of accidents, amputations and disabilities, but the issue of affordability stings certain sections of the society. The regions that have the major share of the market as well as research going on are North America (U.S. and Canada), Latin America (Mexico and Brazil), Asia Pacific (Japan, India, and China), and Europe (Germany and UK).

The future of neuroprosthetics will have research and technology on improving the existing implants; making artificial alternatives for senses other than sight and sound; extensive development of the brain-machine interface; and definitely focusing on making it more accessible and affordable for the common people. Neuroprosthetics has already provided hundreds of individuals the capability to move and regain essential functions lost after their paralysis, and with the recent amount of extensive research, there is a bright future for the field and hope in the domain of biomedicine.

 

 

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