Sensory integration does not lead to sensory calibration
- Jeroen B. J. Smeets*,†,‡,
- John J. van den Dobbelsteen*,§,
- Denise D. J. de Grave*,†,
- Robert J. van Beers*,¶, and
- Eli Brenner*,†
- *Afdeling Neurowetenschappen, Erasmus MC, P.O. Box 1738, NL-3000 DR, Rotterdam, The Netherlands; and
- †Faculty of Human Movement Sciences, Vrije Universiteit, NL-1081 BT, Amsterdam, The Netherlands
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Edited by Dale Purves, Duke University Medical Center, Durham, NC, and approved October 9, 2006 (received for review September 2, 2006)
Abstract
One generally has the impression that one feels one's hand at the same location as one sees it. However, because our brain deals with possibly conflicting visual and proprioceptive information about hand position by combining it into an optimal estimate of the hand's location, mutual calibration is not necessary to achieve such a coherent percept. Does sensory integration nevertheless entail sensory calibration? We asked subjects to move their hand between visual targets. Blocks of trials without any visual feedback about their hand's position were alternated with blocks with veridical visual feedback. Whenever vision was removed, individual subjects' hands slowly drifted toward the same position to which they had drifted on previous blocks without visual feedback. The time course of the observed drift depended in a predictable manner (assuming optimal sensory combination) on the variable errors in the blocks with and without visual feedback. We conclude that the optimal use of unaligned sensory information, rather than changes within either of the senses or an accumulation of execution errors, is the cause of the frequently observed movement drift. The conclusion that seeing one's hand does not lead to an alignment between vision and proprioception has important consequences for the interpretation of previous work on visuomotor adaptation.
Footnotes
- ‡To whom correspondence should be addressed at: Faculty of Human Movement Sciences, Vrije Universiteit, van der Boechorststraat 9, NL-1081 BT Amsterdam, The Netherlands. E-mail: j.smeets{at}fbw.vu.nl
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Author contributions: J.B.J.S. and J.J.v.d.D. designed research; J.B.J.S., D.D.J.d.G., and R.J.v.B. performed research; J.B.J.S. and R.J.v.B. analyzed data; and J.B.J.S., R.J.v.B., and E.B. wrote the paper.
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↵ §Present address: Department of Biomechanical Engineering, Delft University of Technology, NL-2628 CD Delft, The Netherlands.
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↵ ¶Present address: Department Physics of Man, Helmholtz Institute, Utrecht University, NL-3584 CC, Utrecht, The Netherlands.
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The authors declare no conflict of interest.
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This article is a PNAS direct submission.
- Abbreviation:
- CRT,
- cathode ray tube.
- © 2006 by The National Academy of Sciences of the USA
