Psychophysical Characterization of Osseoperception Across Upper-Limb Bony Landmarks.

Somatosensory feedback is essential for fine motor control, yet it remains a challenge to restore it in assistive technologies such as prostheses or exoskeletons. This study investigates osseoperception-the perception of vibrotactile and auditory sensations through bone conduction- a feedback approach that has unique advantages but is rarely considered in literature. We have systematically assessed the psychometric properties of this method across four anatomical sites: the pisiform bone (PB) at the wrist, the olecranon (OL) at the elbow, the clavicle (CL) at the shoulder, and the mastoid process (MP) at the head. Twelve healthy participants underwent four psychophysical experiments to assess sensation discrimination, perception thresholds (PTs), and just-noticeable differences (JNDs) for amplitude and frequency. All tests have been performed at three frequencies (low, medium and high), except for JND, which was determined at two frequencies (low and high). Vibrotactile sensations predominated at low frequencies, whereas auditory sensations emerged at higher frequencies. PB and OL exhibited similar psychometric responses, mostly eliciting vibrations and mixed vibro-auditory sensations, while CL showed responses more comparable to MP, including a higher probability of occurrence of mixed and auditory sensations. PT showed significant differences, whereas JND did not differ significantly across the three upper limb landmarks (PB, OL and CL). Overall, these findings demonstrate that multiple upper-limb bony landmarks can reliably evoke osseoperceptive sensations, supporting their potential use as a single-channel multimodal feedback interface in assistive technologies, both wearable and implantable. The present study shows that there is flexibility in the placement of the bone transducer, which can be chosen based on the requirements of a specific application (e.g., OL for transradial amputation, and CL for transhumeral amputations).