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Crossing the hands increases illusory self-touch.

Pozeg P, Rognini G, Salomon R, Blanke O - PLoS ONE (2014)

Bottom Line: Abundant data show that crossed arms posture impairs remapping of tactile stimuli from somatotopic to external space reference frame and deteriorates performance on several tactile processing tasks.The strength of illusory self-touch was measured with questionnaire ratings and proprioceptive drift.Our results showed that, during synchronous tactile stimulation, the strength of illusory self-touch increased when hands were crossed compared to the uncrossed posture.

View Article: PubMed Central - PubMed

Affiliation: Center for Neuroprosthetics, School of Life Science, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Laboratory of Cognitive Neuroscience, Brain Mind Institute, School of Life Science, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.

ABSTRACT
Manipulation of hand posture, such as crossing the hands, has been frequently used to study how the body and its immediately surrounding space are represented in the brain. Abundant data show that crossed arms posture impairs remapping of tactile stimuli from somatotopic to external space reference frame and deteriorates performance on several tactile processing tasks. Here we investigated how impaired tactile remapping affects the illusory self-touch, induced by the non-visual variant of the rubber hand illusion (RHI) paradigm. In this paradigm blindfolded participants (Experiment 1) had their hands either uncrossed or crossed over the body midline. The strength of illusory self-touch was measured with questionnaire ratings and proprioceptive drift. Our results showed that, during synchronous tactile stimulation, the strength of illusory self-touch increased when hands were crossed compared to the uncrossed posture. Follow-up experiments showed that the increase in illusion strength was not related to unfamiliar hand position (Experiment 2) and that it was equally strengthened regardless of where in the peripersonal space the hands were crossed (Experiment 3). However, while the boosting effect of crossing the hands was evident from subjective ratings, the proprioceptive drift was not modulated by crossed posture. Finally, in contrast to the illusion increase in the non-visual RHI, the crossed hand postures did not alter illusory ownership or proprioceptive drift in the classical, visuo-tactile version of RHI (Experiment 4). We argue that the increase in illusory self-touch is related to misalignment of somatotopic and external reference frames and consequently inadequate tactile-proprioceptive integration, leading to re-weighting of the tactile and proprioceptive signals.The present study not only shows that illusory self-touch can be induced by crossing the hands, but importantly, that this posture is associated with a stronger illusion.

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Related in: MedlinePlus

Questionnaire scores and proprioceptive drift results in the visual RHI.Left panel showing the average ratings of the questionnaire items for three different hand postures in the visual RHI paradigm (Experiment 4). The average ratings indicate that participants experienced the illusion (first three items). However, the posture manipulations did not affect the intensity of the illusion. The error bars represent the standard error of the mean. Right panel showing average proprioceptive drift measures in the visual RHI paradigm (Experiment 4) for the three hand postures. The differences between the three conditions did not reach the level of significance. The error bars represent the standard error of the mean.
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pone-0094008-g004: Questionnaire scores and proprioceptive drift results in the visual RHI.Left panel showing the average ratings of the questionnaire items for three different hand postures in the visual RHI paradigm (Experiment 4). The average ratings indicate that participants experienced the illusion (first three items). However, the posture manipulations did not affect the intensity of the illusion. The error bars represent the standard error of the mean. Right panel showing average proprioceptive drift measures in the visual RHI paradigm (Experiment 4) for the three hand postures. The differences between the three conditions did not reach the level of significance. The error bars represent the standard error of the mean.

Mentions: There were no significant differences between the three conditions in the proprioceptive drift (F(2,12) = 0.712, p = .510, ηp2 = 0.106). The results are shown in Figure 4.


Crossing the hands increases illusory self-touch.

Pozeg P, Rognini G, Salomon R, Blanke O - PLoS ONE (2014)

Questionnaire scores and proprioceptive drift results in the visual RHI.Left panel showing the average ratings of the questionnaire items for three different hand postures in the visual RHI paradigm (Experiment 4). The average ratings indicate that participants experienced the illusion (first three items). However, the posture manipulations did not affect the intensity of the illusion. The error bars represent the standard error of the mean. Right panel showing average proprioceptive drift measures in the visual RHI paradigm (Experiment 4) for the three hand postures. The differences between the three conditions did not reach the level of significance. The error bars represent the standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3974858&req=5

pone-0094008-g004: Questionnaire scores and proprioceptive drift results in the visual RHI.Left panel showing the average ratings of the questionnaire items for three different hand postures in the visual RHI paradigm (Experiment 4). The average ratings indicate that participants experienced the illusion (first three items). However, the posture manipulations did not affect the intensity of the illusion. The error bars represent the standard error of the mean. Right panel showing average proprioceptive drift measures in the visual RHI paradigm (Experiment 4) for the three hand postures. The differences between the three conditions did not reach the level of significance. The error bars represent the standard error of the mean.
Mentions: There were no significant differences between the three conditions in the proprioceptive drift (F(2,12) = 0.712, p = .510, ηp2 = 0.106). The results are shown in Figure 4.

Bottom Line: Abundant data show that crossed arms posture impairs remapping of tactile stimuli from somatotopic to external space reference frame and deteriorates performance on several tactile processing tasks.The strength of illusory self-touch was measured with questionnaire ratings and proprioceptive drift.Our results showed that, during synchronous tactile stimulation, the strength of illusory self-touch increased when hands were crossed compared to the uncrossed posture.

View Article: PubMed Central - PubMed

Affiliation: Center for Neuroprosthetics, School of Life Science, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Laboratory of Cognitive Neuroscience, Brain Mind Institute, School of Life Science, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.

ABSTRACT
Manipulation of hand posture, such as crossing the hands, has been frequently used to study how the body and its immediately surrounding space are represented in the brain. Abundant data show that crossed arms posture impairs remapping of tactile stimuli from somatotopic to external space reference frame and deteriorates performance on several tactile processing tasks. Here we investigated how impaired tactile remapping affects the illusory self-touch, induced by the non-visual variant of the rubber hand illusion (RHI) paradigm. In this paradigm blindfolded participants (Experiment 1) had their hands either uncrossed or crossed over the body midline. The strength of illusory self-touch was measured with questionnaire ratings and proprioceptive drift. Our results showed that, during synchronous tactile stimulation, the strength of illusory self-touch increased when hands were crossed compared to the uncrossed posture. Follow-up experiments showed that the increase in illusion strength was not related to unfamiliar hand position (Experiment 2) and that it was equally strengthened regardless of where in the peripersonal space the hands were crossed (Experiment 3). However, while the boosting effect of crossing the hands was evident from subjective ratings, the proprioceptive drift was not modulated by crossed posture. Finally, in contrast to the illusion increase in the non-visual RHI, the crossed hand postures did not alter illusory ownership or proprioceptive drift in the classical, visuo-tactile version of RHI (Experiment 4). We argue that the increase in illusory self-touch is related to misalignment of somatotopic and external reference frames and consequently inadequate tactile-proprioceptive integration, leading to re-weighting of the tactile and proprioceptive signals.The present study not only shows that illusory self-touch can be induced by crossing the hands, but importantly, that this posture is associated with a stronger illusion.

Show MeSH
Related in: MedlinePlus