Identifying patterns of proprioception and target matching acuity in healthy humans

Traditional approaches to measurement in upper-limb therapy have gaps that electronic sensing and recording can help fill. We highlight shortcomings in current kinematic recording devices, and we introduce a wrist sensing device that performs multimodal sensing during single-axis rotation. Our goal is to characterize normative kinesthetic perception and real-world performance as a multimodal sensory "fingerprint" that can serve as a reference point for identifying deficit in persons affected by stroke, and then as a jumping point for later neuroscientific interrogation. We present an experiment involving psychophysical measurements of passive stimuli discrimination, matching adjustment acuity, and ADL performance in 11 neurologically-intact persons. We found that passive velocity sense and active position sense of healthy controls, measured by velocity discrimination and position matching respectively, correlated in rank with each other, but other score comparisons of acuity or task performance had no statistically significant correlations. We also found that participants differed in acuity between passive and active velocity sense, which supports current understanding about muscle spindle activation being modulated by conscious motor command. The potential for our null correlation results to reveal dissociable aspects of deficit is discussed, as well as implications for future neuroscientific study with more kinematic measures and larger datasets.

Towards an understanding of how humans perceive stiffness during bimanual exploration

In this paper, an experimental testbed and associated psychophysical paradigm are presented for understanding how people discriminate torsional stiffness using wrist rotation about their forearm. Featured in the testbed are two 1-DoF rotary kinesthetic haptic devices. An adaptive staircase was used to evaluate JNDs for a stiffness discrimination task where participants explored virtual torsion springs by rotating their forearms. The JNDs were evaluated across seven different conditions, under four different exploration modes: bimanual, unimanual, bimanual feedback for unimanual displacement, and unimanual feedback for bimanual displacement. The discrimination results will inform future investigation into understanding how stiffness percepts vary.