BIONIC LIMBS : THE ARTIFICIAL LIMBS THAT LIVE
by Deepa Sebastien, St. Stephen’s College
For long has the Jaipur Foot 'walked', and it's only fair that its journey of countless suns culminates at the altar of scientific genius and technological innovation. Keeping in step with the idea of integration of technology into human lives, artificial limbs have evolved in 'leaps' and 'bounds'.
The movement of any body part is controlled by the cortex in the brain, aided by the nervous system and the specialized nerve cells called motor neurons. The ‘will’ to move a body part, in a particular way, originates in the cortex in the form of electrical currents, which are conveyed through the neurons to the specific muscle groups which contract or relax to bring about motion.
If and when a body part becomes numb, there occurs a divorce between the functioning of the brain and the body part. The same is the case with an artificial limb. Any movement of the attached limb is not perceptible to the brain. It is an alien part attached to the biological self, acclimatizing to which would take time. Experiments are underway with the aim of making artificial limbs respond to natural neural control of motor activities using complex processes and specialized chips. The electrical current issued by the neurons in the cortex are read and transferred to the artificial limb which in turn, acting like muscles would cause the flexing of the artificial limb, in imitation of a natural limb. This interface between an alien body and the human brain is called the Brain-Machine Interface (BMI). BMI is of two types: Invasive BMI and Non-Invasive BMI. In both cases electrodes are used to read the brain’s activity. The difference lies in the fact that a Non-Invasive BMI uses the electrodes without piercing the brain tissues. The electroencephalogram is one of the earliest Non-Invasive BMI devices.
While the Non-Invasive BMI is able to read the brain’s activity with respect to the electricity passing through the axons of a clump of neurons, the Invasive BMI is capable of reading the electrical activity of a neuron in isolation. In this case, a very slim electrode placed parallel to the axon of a neuron tracks and reads the electrical activity. The bionic limbs are designed so as to provide functionality as well as tactile sensory feedback.
The good news is not only for amputees but also patients of incurable ailments like the motor neuron Alzheimer’s disease. Besides this, the new invention moves outside the paradigm of limb movements to accommodate restoration of communication ability for victims of stroke and other paralytic disorders. This can be achieved by using the method to map and translate thoughts into communicable format using computer programmes, instead of to flex alien parts attached to the body.
Science today is advancing at a fast rate to make life more comfortable and worth living. In his attempt to achieve supremacy and self-betterment, man is moving, probably involuntarily, to a scenario where all activities are controlled by the human brain, at the speed of thought. There might, in the far future, be a situation where people would trade their healthy natural limbs for stronger, synergist, pain-enduring and multi-tasking bionic limbs.