Authors: Myriam Levy Stéphanie Bourgeon C Elaine Chapman
Publish Date: 2006/10/19
Volume: 178, Issue: 2, Pages: 240-251
Abstract
The aim of this study was to define the relative contribution of selfgenerated cutaneous and proprioceptive feedback to haptic shape discrimination by systematically constraining the exploratory strategy Subjects n = 23 explored pairs of twodimensional 2D angles standard angle 90° comparison angles 91°–103° placed at arm’s length from the subject and identified the larger angle of each pair The exploratory strategies included a reference condition dynamic scan of the index finger over the entire object combined cutaneous and proprioceptive shoulder feedback and modified conditions static touch of the intersection of the two bars that formed the angle using the index finger cutaneous feedback and dynamic scans of the object using a handheld tool proprioceptive feedback shoulder Discrimination thresholds 75 correct were very similar for dynamic and static touch with the index finger Thresholds varied as a function of the static contact duration 1 s 72° ± 06° ∼3 s 42° ± 05° but were not different from the reference condition 60° ± 09° The higher threshold with short static touch likely reflects movementrelated gating of selfgenerated tactile inputs Together the results suggested that cutaneous feedback alone may be sufficient to explain 2D angle discrimination because the added proprioceptive feedback did not improve performance Also threshold did not vary with the number of dynamic scans one or two suggesting that the critical information was gathered on the first pass over the angle In contrast when the angles were explored with the tool the threshold increased relative to the corresponding reference condition from the same session tool 96° ± 09° dynamic scan with the finger 62° ± 10° Thus performance was poorer with proprioceptive feedback alone suggesting that cutaneous feedback was relatively more important for 2D haptic angle discrimination in the present experimentThe authors would like to thank the following for the excellent technical assistance provided René Albert Jacques Bérichon MarieThérèse Parent Gaétan Richard and Christian Valiquette We also thank Trevor Drew and Allan Smith for helpful comments on the manuscript and ElMehdi Meftah for helpful suggestions throughout the course of the experiments Funding from the Natural Sciences and Engineering Research Council of Canada NSERC and the Canadian Institutes of Health Research CIHR individual and group grants are gratefully acknowledged Stéphanie Bourgeon was supported in part by a bursary from the GRSNC Groupe de la recherche sur le système nerveux central a group supported by the Fonds de la recherche en santé du Québec FRSQ and the Université de Montréal
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