Rehabilitation through Brain Machine Interfaces

Stephen Hawking: Former Lucasian Professor of Mathematics at the University of Cambridge, world renowned theoretical physicist, diagnosed with Amyotrophic Lateral Sclerosis (ALS) at the age of 21

Christopher Reeves: American film actor, fondly remembered for his motion-picture portrayal of the fictional superhero Superman; suffered a spinal cord injury and became a quadriplegic at the age of 43

These are probably some of the first names which pop up when we think of people living with disability and the need for rehabilitation technologies. A severe form of disability arises because of limb amputations as an after effect of traumatic accidents, degenerative diseases or victims of a social disorder.

These conditions often mean drastic lifestyle changes for the disabled, worsened with limited means of livelihood, social disconnect and dependability. Restoring mobility for such patients is a goal of many research teams around the globe, most focusing on repairing the damaged nerves and trying to find ways for nerve signals to bypass the injury site. Another approach is to build prosthetic devices which are essentially closed-loop architectures based on biofeedback (EMG, EEG etc) signals.

Brain Machine Interface (BMI) is a recent technological advancement which taps the brain waves using surface EEG electrodes which are subsequently used to control a prosthetic device. The guiding premise in the design of such interfaces is the following:

The two activities of actually moving a real arm and just thinking about moving the arm produce same neuronal firing in the brain.

A smart wheelchair based on this premise could be a system having an EEG cap to non-invasively acquire the signals from the patient’s primary motor cortex area in the brain, and deploy a real-time pattern recognition algorithm to identify the mental states of the patient – whether he is thinking ‘left’, or ‘right’ or is idle, and subsequently control a wheelchair based on these inputs. The EEG cap however, as opposed to implanted neurochips has a limited bandwidth but at the same time is free from complications because of surgical procedures.

In an attempt to develop prosthetic technology capable of restoring motor control and tactile feedback to spinal cord injury patients, an interesting experimental study was reported in Nature where researchers from Duke University Center for Neuroengineering had successfully trained two monkeys to use the electrical activity in their motor cortex to control the arm of an onscreen avatar without physically moving themselves, hinting at the possibilities of wearable thought – controlled prosthetic devices in the near future.

A recent case report from Cornell University represents the first successful demonstration of a BCI-controlled lower extremity prosthesis for independent ambulation, which might allow for a cheap, easy, and non-invasive option to getting paraplegics walking again. A wireless brain-machine interface developed by Neural Signals uses implantable electrodes to address Locked-In syndrome for jaw movements, a terrifying brain lesion which leaves patients aware but almost entirely without the power to move.

However fascinating these new developments seem to be, they are far from a commercial reality. The non invasive systems suffer from poor spatial and temporal resolutions, driving the quest to devise more powerful and usable brain recording devices. The medical community would benefit for sure, but possibilities are limitless – gaming, cursor control, brain timing and brain-to-brain communication to name a few. And who knows, it might also open an unethical dimension of hacking the brain!

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