AbstractBeyond visual feedback, somatosensory feedback provides information to help determine limb locations and movement accuracy. Previously we found that induced paresthesia removed the predicted movement time (MT) and time to peak velocity (ttPV) differences for reaching movements in vision and no vision conditions. Induced paresthesia also led to early end-position bias, but only when vision of limb was unavailable. The present study investigated if adding auditory feedback for accurate reaching trials improves reaching movements when vision is removed. Fourteen healthy right-handed participants (9 males, M=22.7[SD=2.9] years), performed 400 reaching movements over two days. Four possible targets were paired with four experimental condition combinations: Vision/No Vision; Paresthesia/No Paresthesia. Order of the target locations and visual targets were blocked and counterbalanced. Visual feedback was removed using visual occlusion spectacles (PLATO, Translucent Technologies). Median nerve paresthesia was temporarily induced using a constant current stimulator (DS7AH, Digitimer), and standardized sensory testing confirmed disrupted feedback. Participants were motivated to improve their MTs while maintaining endpoint accuracy with incentives for accurate movements with shorter MTs. Movements were recorded using a 3D motion analysis system at 300Hz (Optotrak-3D Investigator, NDI) and analyzed using a 2 Vision by 2 Paresthesia by 2 Performance (Early trials/Late trials) repeated measures ANOVA. Analyses revealed that participants’ reaction times improved with practice, MTs remained unchanged. A Vision by Early/Late Performance interaction revealed that participants decreased their ttPV only when vision was available (early=192ms; late=179ms). A Paresthesia by Movement Proportion by Performance interaction revealed that with paresthesia trial-trial variability of the limb position increased from early to late performance, however, a difference was no longer present at endpoint. In contrast, limb position variability decreased from early to late performance when paresthesia was not present. The present results support the use of auditory cues to mitigate the detrimental effect of paresthesia on movement accuracy.
Acknowledgments: This project was funded by Manitoba Medical Service Foundation, Manitoba Health Research Council and Natural Sciences and Engineering Research Council. We would like to thank Brie Page, Tamires Prado and Aric Bremer for their help with data collection.