activate the human auditory cortex. Currently vibrotactile stimuli can be used to facilitate hearing in normal and hearing-impaired people. To test for the auditory areas activated by touch, Schurmann et al. tested subjects while stimulating their fingers and palms with vibration bursts and their fingertips with tactile pressure. They found that tactile stimulation of the fingers lead to activation of the auditory belt area, which suggests that there is a relationship between audition and tactition. Therefore, future research can be done to investigate the likelihood of a tactile–auditory sensory substitution system. One promising invention is the 'Sense organs synthesizer' which aims at delivering a normal hearing range of nine octaves via 216 electrodes to sequential touch nerve zones, next to the spine. Tactile–vestibular Some people with balance disorders or adverse reactions to antibiotics develop bilateral vestibular damage (BVD). They experience difficulty maintaining posture, unstable gait, and oscillopsia. Tyler et al. studied the restitution of postural control through a tactile for vestibular sensory substitution. Because BVD patients cannot integrate visual and tactile cues, they have a lot of difficulty standing. Using a head-mounted accelerometer and a brain–computer interface that employs electrotactile stimulation on the tongue, information about head-body orientation was relayed to the patient so that a new source of data is available to orient themselves and maintain good posture. Tactile–tactile to restore peripheral sensation Touch to touch sensory substitution is where information from touch receptors of one region can be used to perceive touch in another. For example, in one experiment by Bach-y-Rita, the touch perception was restored in a patient who lost peripheral sensation from leprosy. For example, this leprosy patient was equipped with a glove containing artificial contact sensors coupled to skin sensory receptors on the forehead (which was stimulated). After training and acclimation, the patient was able to experience data from the glove as if it was originating in the fingertips while ignoring the sensations in the forehead. After two days of training one of the leprosy subjects reported "the wonderful sensation of touching his wife, which he had been unable to experience for 20 years." Tactile feedback system for prosthetic limbs The development of new technologies has now made it plausible to provide patients with prosthetic arms with tactile and kinesthetic sensibilities. While this is not purely a sensory substitution system, it uses the same principles to restore perception of senses. Some tactile feedback methods of