Please cite this article in press as: A. Yoshimura, et al., Blind humans rely on muscle sense more than normally sighted humans for guiding goal-directed movement, Neurosci. Lett. (2010), doi:10.1016/j.neulet.2010.01.035 ARTICLE IN PRESS G Model NSL-26769; No. of Pages 4 Neuroscience Letters xxx (2010) xxx–xxx Contents lists available at ScienceDirect Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet Blind humans rely on muscle sense more than normally sighted humans for guiding goal-directed movement Atsuko Yoshimura a , Akiyoshi Matsugi a , Yoshihisa Esaki b , Koichi Nakagaki c , Koichi Hiraoka d,∗ a Osaka Prefecture University, Graduate School of Comprehensive Rehabilitation, Japan b Osaka Prefectural Special Needs Education School for the Visually Impaired, Japan c Osaka City School for the Blind, Japan d Osaka Prefecture University, School of Comprehensive Rehabilitation, Habikino 3-7-30, Habikino City, Osaka 583-8555, Japan article info Article history: Received 4 December 2009 Received in revised form 10 January 2010 Accepted 15 January 2010 Keywords: Blind Muscle sense Vibration Motor control abstract The purpose of this study was to investigate whether totally blind humans rely on muscle sense for guid- ing goal-directed movement more than do blindfolded normally sighted humans. Twelve totally blind humans and 12 blindfolded normally sighted humans performed goal-directed movement. The subjects rapidly extended the elbow to a target angle in response to an auditory start cue while a vibration was applied to the antagonist muscle. Verbal feedback, concerning whether the movement was terminated near the target angle, was given immediately after each trial. Through these trials, the subjects acquired a movement terminating near the target angle. Immediately after these trials, the same movement was performed 20 times without the vibration and the verbal feedback. In the trials without the vibration and verbal feedback, the terminal angle of the movement was overshot as a reference to the last 5 trials where there was the vibration and verbal feedback. The amount of overshooting in the blind humans was significantly larger than that in blindfolded normally sighted humans. These findings indicate that for guiding goal-directed movement blind humans rely on their muscle sense more than do normally sighted humans. © 2010 Elsevier Ireland Ltd. All rights reserved. Behavioral and brain reorganizations take place after long-term sensory deprivation, and often lead to compensatory plasticity in the processing of spared modalities [2,16]. This view has been sup- ported by several previous findings showing that blind humans outperform normally sighted humans in tactile [1,10,24] or kines- thetic acuity [13]. Furthermore, this view may apply to the guiding of arm and hand movements in cases where there is no vision. When vision is deprived in normally sighted humans, proprio- ception suffices for the adaptive recovery of hand trajectories performing goal-directed reaching [22]. Blind humans have pro- duced straighter hand-path curvature in reaching movements than have blindfolded normally sighted humans [23]. Proprioceptive spatial acuity in adult congenitally blind humans has been shown to depend on their non-visual spatial experience during early devel- opment [7]. In addition, absolute distance errors during a pointing task in blind humans have been found to be smaller than those in blindfolded normally sighted humans [9]. Proprioception should be the dominant sensation for guiding arm and hand movements when vision is deprived because nor- mally sighted humans guide arm and hand movements mainly with ∗ Corresponding author. Tel.: +81 72 950 2875; fax: +81 72 950 2131. E-mail address: hiraoka@rehab.osakafu-u.ac.jp (K. Hiraoka). both vision and proprioception [20,21]. A previous finding, which showed that kinesthetic localization by blind children was supe- rior to that by normally sighted children [13], supports the view that blind humans rely on proprioception more than do normally sighted humans. In contrast, however, a previous study had pro- duced contradictory evidence that hand orientation guided only by proprioception was similar between blind humans and blind- folded normally sighted humans, thus indicating that normally sighted humans can use proprioception alone for guiding their per- formances as efficiently as blind humans [12]. Therefore, there is no consensus concerning the compensational use of proprioception for guiding arm and hand movements in blind humans. Muscle sense is the most important component of propriocep- tion, and, therefore, its investigation in blind humans is important for understanding the role of proprioception in guiding arm or hand movement in blind humans. However, this has not been investi- gated so far. Muscle spindles are sensitive to vibratory stimulation [3,4,6], especially the muscle spindle primary endings [18]. Vibra- tory stimulation to this muscle produces the illusion of movement in the direction in which the vibrated muscle is stretched [5,11]. Based on these previous findings, we utilized vibratory stimulation in the present study for producing an illusory muscle sense. The purpose of this study was to investigate if blind patients in guiding goal-directed movement rely on muscle sense more 0304-3940/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2010.01.035