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Repairing and Virtualising Balance in one Swoop

The vestibular system is tiny, an almost insignificant part of the inner ear. Yet, if we lose it, simple movement becomes all but impossible. Without the vestibular system we lose our sense of balance entirely. This means that if you stand in a dark room with no light, you cannot tell up from down, left from right. Without a balance system keeping us upright in the physical world, the world wavers with every step as our bodty swings left to right with no natural correction. Falls become random, as even when walking in a straight line your body may tip further and further over without you being aware of it, intil a critical tipping point is reached, and you are sprawled on the floor.

Balance is vital in the physical world. In the virtual, it is not yet vital, but would be handy for an increasing number of situations. One situation that is not with us yet, but has started to peek over the horizon, is the use of full body motion control in virtual environments. This would give us full control over realistically boned and jointed avatars. However, they would be without natural balance, as that is a sub-conscious part of our make-up, and the danger is we would find ourselves behaving in the virtual world, the same way a person without a vestibular system behaves in the physical one.

The inner ear functions like a gyroscope. Three orthogonally oriented structures, called the semicircular canals, sense the orientation of the head via movement of fluid within the canals. Nerves connected to these structures send a train of neural signals to the brain, which integrates that information with visual signals and other cues to maintain balance and stabilize vision. One of many effects this has is to keep our vision centred as we walk, eliminating the jittery, handheld-camera effect we would otherwise have to process.

Previous attempts at augmenting an existing vestibular system have been trialed, ways that turn it into an input device for VR, and which can control balance feedback - making a person instinctively know they are falling forwards end over end, when in fat they are sitting on a normal chair in a quiet room. One immensely successful method is termed galvanic vestibular stimulation. Galvanic vestibular stimulation is a method of controlling and constraining natural balance and movement ranges by using two weak electrical fields, delivered just behind the earlobes to control a person's vestibular system, control nexus for the twin senses of movement and balance.

When a weak DC current is delivered to the mastoid behind a person's ear, their body responds by shifting your balance toward the anode. The stronger the current, the more powerful its pull. If it is strong enough, it not only throws them off balance but alters the course of their movement.

The problem comes when a person's own inner ear is damaged or non functional. In this case, galvanic vestibular stimulation alone does not work, as there is nothing to stimulate. What is needed, is a prosthetic in the ear which instead of aiding hearing, recreates the sense of balance.

Thankfully, the relative simplicity of the vestibular system makes it an ideal target for prosthesis. The horizontally oriented canal, detects left-right motion, such as a negative shake of the head. Neurons that connect to this canal send electrical pulses to the brain at a high rate when the head turns to the left, and a low rate when it turns to the right.

Neuroscience is now just starting to edge into the area of such a balance prosthesis. Dan Merfeld and Richard Lewis, neuroscientists at the Massachusetts Eye and Ear Infirmary, in Boston, are currently testing vestibular implants on monkeys. They are trying to gain proof of concept that would make human surgical procedures viable for consideration.

Merfeld's prosthesis mimics this signaling system: a motion sensor on the head measures rotation, sending that information to a microprocessor that converts it into electrical impulses, which are transferred to an electrode implanted into the inner ear.

Ultimately, this implant would restore horizontal balance control - side to side motion - in an aflicted individual. Once this is achieved, the other two balance sensory groups for the remaining axis will be tackled at an acceperated pace, and ultimately, will enable GVS to function on such individuals, as well as open up exactly how balance neuralsignalling functions, giving us access to the codes for the brain, to bypass our physical sense of balance all together.

When we have that - and that is now definitely a when, not an if, then we will finally be within sight of freeform movement VR, where the brain corrects the balance issues of the avatar itself.

References

VWN Virtual Dictionary: Galvanic Vestibular Stimulation

A Prosthesis for Balance

Remote-Controlled Humans

Staff Comments

 


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