Tapping into tongue motion to substitute or augment upper limbs

Assistive technologies (AT) play an important role in the lives of people with disabilities. Most importantly, they allow individuals with severe physical disabilities become more independence. Inherent abilities of the human tongue originated from its strong representation in the motor cortex, its direct connection to the brain through well-protected cranial nerves, and easy access without a surgery have resulted in development of a series of tongue-operated ATs that tap into the dexterous, intuitive, rapid, precise, and tireless motion of the tongue. These ATs not only help people with tetraplegia as a result of spinal cord injury or degenerative neurological diseases to access computers/smartphones, drive wheelchairs, and interact with their environments but also have the potential to enhance rehabilitation paradigms for stroke survivors. In this paper, various types of tongue operated ATs are discussed based on their working principles and task based performances. Comparisons are drawn based on widely accepted and standardized quantitative measures, such as throughput, information transfer rate, typing speed/accuracy, tracking error, navigation period, and navigation accuracy as well as qualitative measures, such as user feedback. Finally, the prospects of using variations of these versatile devices to enhance human performance in environments that limit hand and finger movements, such as space exploration or underwater operations are discussed.