Vestibular Augmentation and Enhanced Agility Factoring is an eBook in Deus Ex: Human Revolution. It is located in the Derelict Row, in the half-sunken basement area with windows looking out onto an interior courtyard, lying on top of a cluster of four silver barrels being patrolled by gang members (one of them complains about needing to urinate nearby).
The human vestibular system governing our sense of spatial orientation is made up of many sensory inputs and outputs, mediated by reflex actions in the spinal cord, inner ear, nerve impulses, and -- ultimately -- conscious control by the cerebral cortex.
Vestibular augmentation technology, originally developed to help fighter pilots and astronauts counteract effects from G-forces or anti-gravity, has now evolved to a stage where it can be used not only to retain a normal sense of agility, but also to enhance an existing one.
A distributed network of pressure sensitive neural implants can signal a series of integrated circuits to manipulate the vestibulo-ocular reflex (VOR). This is a reflex eye movement that stabilizes images on the retina during head movement by producing an eye movement in the opposite direction, thus preserving the image on the center of the visual field. The system also manipulates the vestibular system within the inner ear.
In other words, by electrically stimulating afferent neurons, the system replaces absent sensory function by providing stimulation that modulates above and below a baseline. When engaged in an “accelerated mode”, it provides a means to override natural variations and enable enhanced control over limbs beyond the standard degrees of freedom.