the brain that is responsible for the final perception, sensory substitution is possible. During sensory substitution an intact sensory modality relays information to the visual perception areas of the brain so that the person can perceive sight. With sensory substitution, information gained from one sensory modality can reach brain structures physiologically related to other sensory modalities. Touch-to-visual sensory substitution transfers information from touch receptors to the visual cortex for interpretation and perception. For example, through fMRI, one can determine which parts of the brain are activated during sensory perception. In blind persons, it is seen that while they are only receiving tactile information, their visual cortex is also activated as they perceive sight objects. Touch-to-touch sensory substitution is also possible, wherein information from touch receptors of one region of the body can be used to perceive touch in another region. For example, in one experiment by Bach-y-Rita, touch perception was able to be restored in a patient who lost peripheral sensation due to leprosy. Technological support In order to achieve sensory substitution and stimulate the brain without intact sensory organs to relay the information, machines can be used to do the signal transduction, rather than the sensory organs. This brain–machine interface collects external signals and transforms them into electrical signals for the brain to interpret. Generally, a camera or a microphone is used to collect visual or auditory stimuli that are used to replace lost sight and hearing, respectively. The visual or auditory data collected from the sensors is transformed into tactile stimuli that are then relayed to the brain for visual and auditory perception. Crucially, this transformation sustains the sensorimotor contingency inherent to the respective sensory modality. This and all types of sensory substitution are only possible due to neuroplasticity. Brain plasticity Brain plasticity refers to the brain's ability to adapt to a changing environment, for instance to the absence or deterioration of a sense. It is conceivable that cortical remapping or reorganization in response to the loss of one sense may be an evolutionary mechanism that allows people to adapt and compensate by using other senses better. Brain imaging studies have shown that upon visual impairments and blindness (especially in the first 12–16 years of life) the visual cortices undergo a huge functional reorganization such that they are activated by other sensory modalities. Such cross-modal plasticity was also found through functional imaging of congenitally blind patients which showed