Edinburgh Research Explorer Sensory augmentation

Bio-mimetic approaches to restoring sensory function show great promise in that they rapidly produce perceptual experience, but have the disadvantage of being invasive. In contrast, sensory substitution approaches are non-invasive, but may lead to cognitive rather than perceptual experience. Here we introduce a new non-invasive approach that leads to fast and truly perceptual experience like biomimetic techniques. Instead of building on existing circuits at the neural level as done in bio-mimetics, we piggy-back on sensorimotor contingencies at the stimulus level. We convey head orientation to geomagnetic North, a reliable spatial relation not normally sensed by humans, by mimicking sensorimotor contingencies of distal sounds via head-related transfer functions. We demonstrate rapid and long-lasting integration into the perception of self-rotation. Short training with amplified or reduced rotation gain in the magnetic signal can expand or compress the perceived extent of vestibular self-rotation, even with the magnetic signal absent in the test. We argue that it is the reliability of the magnetic signal that allows vestibular spatial recalibration, and the coding scheme mimicking sensorimotor contingencies of distal sounds that permits fast integration. Hence we propose that contingency-mimetic feedback has great potential for creating sensory augmentation devices that achieve fast and genuinely perceptual experiences. Starting , and research , that an a of interfacing does by the non-invasively rather level, we contingency-mimetics. this approach by a magnetic-to-auditory augmentation signal that has two aspects: (1) The higher-order magnetic aspect of the contingency that is provided by the electronic compass and establishes the unique novel allocentric spatial stability that we wished to integrate into spatial perception; (2) The lower-order sensory aspect of the contingency that is provided the use of HRTF: The HRTF describes the characteristics with which external sounds arriving from a are filtered by pinnae, head, shoulder and and hence creates a sensory interface that the acoustic signals of spatial coming from a particular This approach thus piggy-backs the of a head-based compass on cues of distal sounds. The spatial information can this way interface with existing spatial processes via natural mechanisms of localization. to by physiological of modality While vision tends to dominate the of space, vestibular calibration , this role might be taken over by an artificial signal with equal (or higher) allocentric spatial reliability, provided that it is processed as a spatial signal by the perceptual system. Compatible with this claim, our behavioral results show that auditory information has led the vestibular system to recali-brate, rather than the other way around, and that it has done this with a similar magnitude as has been observed from re-calibration from optic flow 35,58 , which normally provides a calibrating spatial signal. Further, interviews with our participants revealed that for all except five of them (two in experiment 1, three in experiment 2), who report that they perceived it as an object rotating in space around them, the sound was immediately and reliably perceived as coming from a stable direction. These findings suggest that the sensorimotor processes main- taining spatial calibration have estimated the novel magnetic-auditory spatial reference as being world-stationary despite its bias and attributed its divergence with the vestibular information to internal-vestibular causes (errors in self-rotation estimation) rather than to external-auditory causes 71 , leading, potentially aided by priors for sta-tionary external auditory sources , to a recalibration of internal-vestibular rotation estimates, i.e. of vestibular spatial perception. This opens the interesting prospect that a magnetic reference provided via auditory contingency-mimicry in a mobile device might lead the brain to intuitively utilize the stability of an artificial ‘magnetic reference’ for spatial calibration also in more natural behavior, with potential for improving navigation and for the compensation of spatial disabilities such as blindness or vestibular loss. Future studies might for example test if a magnetic-auditory allocentric reference of the head can diminish errors in perceived self-rotation during natural locomotion Further, a head-centered auditory reference might allow to compensate deficiencies in the allocentric calibra- tion of vestibular position estimates in congenitally blind people , to