Using Virtual Spatialized Auditory Displays to Restore Proprioceptive Function in Individuals with Prosthetic Limbs
One of the main contributors to motor control deficits in individuals with prosthetic limbs is their lack of proprioceptive feedback. Proprioceptive feedback provides individuals with a sense of relative body position and is critical for accurate motor control. A common method used to restore proprioceptive function in individuals with prosthetic limbs is sensory substitution, which involves circumventing the loss of proprioceptive function by replacing it with another sense. One promising form of sensory substitution that has not yet been explored in the context of prosthetics is spatialized auditory-proprioceptive substitution, in which spatialized audio displays simulate a sound coming from a specific point in space. In this context, using audio to identify limb position could circumvent the loss of proprioceptive function. Specifically, head-related transfer functions (HRTFs), which identify the characteristics of a sound entering an ear from a specific point in space, could be used to deliver spatialized auditory cues through headphones to participants to substitute proprioception. This review explores past studies on overall localization performance, the extent to which HRTFs tailored to the individual provide improve localization performance, and the merits of using headtracking technology to alter auditory output in real time. It is expected that using generalized HRTFs will lead to good localization performance, and that individualized HRTFs with headtracking will lead to even better performance. This review will provide a basis for developing easily-perceived spatialized auditory displays, which will eventually be used to test the auditory-proprioceptive substitution hypothesis in the context of proprioceptive loss in individuals with prosthetics.