| Abstract No.: | B-D2147 |
| Country: | Canada |
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| Title: | THE INFLUENCE OF VISUAL-PROPRIOCEPTIVE INTEGRATION ON SENSE OF LIMB POSITION |
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| Authors/Affiliations: | 2 Erin K. Cressman*; 1 Denise Y.P. Henriques;
1 Centre for Vision Research, School of Kinesiology and Health Science, Department of Psychology, York University; 2 Centre for Vision Research, York University, Toronto, ON, Canada
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| Content: | Objective: Our sense of limb position can be derived from both visual and proprioceptive signals. It is currently unclear how these sources of information are integrated. According to Smeets and colleagues (2006), when information is available from both modalities, visual and proprioceptive signals are combined to form a coherent estimate of where the limb is in space. Furthermore, Smeets argues that integrating visual and proprioceptive signals does not lead to mutual calibration (i.e. one does not align visual and proprioceptive information). In the current study we examined this proposal when no efferent signals regarding changes in limb position were present. Specifically, we compared subjects’ ability to judge the position of their unseen limb, which had been passively moved, before and after the opportunity to align proprioceptive with visual information.
Materials and Methods: To assess subjects’ perception of limb position, subjects grasped the handle of a robot manipulandum, which passively moved the limb 10 cm outwards from a home position. At the end of the movement a target appeared and subjects made a two-alternative forced choice (2-AFC) judgment regarding the position of their hand (left or right) relative to the target. Visual targets were located 5, 30, 45 and 60 degrees to the left and right of centre. A centre target was also included and represented visually or by an auditory beep. If a beep sounded, subjects indicated if their limb was to the left or right of their midline. The angle of the hand with respect to the target was adjusted over trials using a 2-AFC adaptive staircase algorithm, decreasing if the response was consistent with the previous one and increasing if it was not. Testing began with subjects completing this limb-target estimation task. Subjects then received visual feedback regarding the position of their limb as they made active aiming movements to visual targets located 5, 30 and 60 degrees to the left and right of centre. Finally, the limb-target estimation task was completed a second time.
Results: To quantify subjects’ estimates of hand position with respect to each target, we fitted a logistic function to the data to define the bias (accuracy: position at which participants reported left and right equally often), and the uncertainty range (precision: the difference between the values at which the response probability was 25 and 75%). We found that subjects more accurately estimated the position of their limb the second time, after having received concurrent visual and proprioceptive information regarding the position of their limb. Subjects’ estimates were also more consistent, as precision decreased after subjects performed the active aiming movements.
Conclusion: Thus, given the improvement in subjects’ ability to localize a passively moved limb with respect to a target, our results indicate that if given the opportunity, visual and proprioceptive information are aligned. Future work will continue to examine intersensory calibration by determining the influence of misaligned visual feedback on sense of limb position.
Acknowledgments: CIHR Training Grant and NSERC PDF (to EKC), CIHR (to DYPH).
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