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Neural substrate of body size: illusory feeling of shrinking of the waist.

Ehrsson HH, Kito T, Sadato N, Passingham RE, Naito E - PLoS Biol. (2005)

Bottom Line: We found that activity in the cortices lining the left postcentral sulcus and the anterior part of the intraparietal sulcus reflected the illusion of waist shrinking, and that this activity was correlated with the reported degree of shrinking.These results suggest that the perceived changes in the size and shape of body parts are mediated by hierarchically higher-order somatosensory areas in the parietal cortex.Based on this finding we suggest that relative size of body parts is computed by the integration of more elementary somatic signals from different body segments.

View Article: PubMed Central - PubMed

Affiliation: Wellcome Department of Imaging Neuroscience, Institute of Neurology, London, United Kingdom. h.ehrsson@fil.ion.ucl.ac.uk

ABSTRACT
The perception of the size and shape of one's body (body image) is a fundamental aspect of how we experience ourselves. We studied the neural correlates underlying perceived changes in the relative size of body parts by using a perceptual illusion in which participants felt that their waist was shrinking. We scanned the brains of the participants using functional magnetic resonance imaging. We found that activity in the cortices lining the left postcentral sulcus and the anterior part of the intraparietal sulcus reflected the illusion of waist shrinking, and that this activity was correlated with the reported degree of shrinking. These results suggest that the perceived changes in the size and shape of body parts are mediated by hierarchically higher-order somatosensory areas in the parietal cortex. Based on this finding we suggest that relative size of body parts is computed by the integration of more elementary somatic signals from different body segments.

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Activity that Reflects the Illusion that the Waist Was Shrinking (Interaction Effect: p < 0.001 Uncorrected)Top row: Activation of the cortices lining postcentral sulcus near its junction with the intraparietal sulcus. Lower row: Activation of cortex lining the intraparietal sulcus. The activations (colour) are superimposed on a normalized high-resolution T1-weighted image of a representative participant (black and white). The coordinates for the displayed slices are shown, and the crossing of the blue lines indicates the location of the activation peaks. R and L denote the right and left hemispheres, respectively. The plots to the right show the contrast estimates with the standard bars corresponding to the standard error (SE).
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pbio-0030412-g002: Activity that Reflects the Illusion that the Waist Was Shrinking (Interaction Effect: p < 0.001 Uncorrected)Top row: Activation of the cortices lining postcentral sulcus near its junction with the intraparietal sulcus. Lower row: Activation of cortex lining the intraparietal sulcus. The activations (colour) are superimposed on a normalized high-resolution T1-weighted image of a representative participant (black and white). The coordinates for the displayed slices are shown, and the crossing of the blue lines indicates the location of the activation peaks. R and L denote the right and left hemispheres, respectively. The plots to the right show the contrast estimates with the standard bars corresponding to the standard error (SE).

Mentions: First, we analysed the activity that reflected the shrinking-body illusion that could not be attributed to the effects of vibrating the wrist tendon or the position of the arms. This activity is given by the interaction term in the factorial design ([tendon contact – skin contact] – [tendon free – skin free]) (see Methods and Methods; Figure 1). We found one cluster of active voxels in the whole brain that was located in the left parietal lobe (size: 200 mm3; p < 0.05 corrected; see Figure 2). The cluster was located in the anterior part of the intraparietal sulcus and extended rostrally to the postcentral sulcus. This cluster contained two distinct peaks of activation (Figure 2). The anterior peak was located in the postcentral sulcus (x = −54, y = −30, z = 57 [x, y, and z coordinates in the standard space of the Montreal Neurological Institute]; t = 4.76; p < 0.001 uncorrected) near the junction of this sulcus and the intraparietal sulcus. The posterior peak was located at the border between the superior parietal convexity and the anterior part of intraparietal sulcus (x = −45, y = −39, z = 60; t = 3.86; p < 0.001 uncorrected). In the right hemisphere, there was a statistical trend for activation in the corresponding parietal sites (intraparietal sulcus: x = 42, −30, 60; t = 2.91; p = 0.005 uncorrected; superior parietal gyrus: x = 48, y = −33, z = 72; t = 3.15; p = 0.003; not shown in the Figures). The activity in the two left parietal foci was not significantly greater than the activity in the right corresponding areas (p > 0.19 uncorrected). Hence, the parietal cortex appears to be bilaterally engaged, albeit with only a statistical trend for activation on the right side.


Neural substrate of body size: illusory feeling of shrinking of the waist.

Ehrsson HH, Kito T, Sadato N, Passingham RE, Naito E - PLoS Biol. (2005)

Activity that Reflects the Illusion that the Waist Was Shrinking (Interaction Effect: p < 0.001 Uncorrected)Top row: Activation of the cortices lining postcentral sulcus near its junction with the intraparietal sulcus. Lower row: Activation of cortex lining the intraparietal sulcus. The activations (colour) are superimposed on a normalized high-resolution T1-weighted image of a representative participant (black and white). The coordinates for the displayed slices are shown, and the crossing of the blue lines indicates the location of the activation peaks. R and L denote the right and left hemispheres, respectively. The plots to the right show the contrast estimates with the standard bars corresponding to the standard error (SE).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1287503&req=5

pbio-0030412-g002: Activity that Reflects the Illusion that the Waist Was Shrinking (Interaction Effect: p < 0.001 Uncorrected)Top row: Activation of the cortices lining postcentral sulcus near its junction with the intraparietal sulcus. Lower row: Activation of cortex lining the intraparietal sulcus. The activations (colour) are superimposed on a normalized high-resolution T1-weighted image of a representative participant (black and white). The coordinates for the displayed slices are shown, and the crossing of the blue lines indicates the location of the activation peaks. R and L denote the right and left hemispheres, respectively. The plots to the right show the contrast estimates with the standard bars corresponding to the standard error (SE).
Mentions: First, we analysed the activity that reflected the shrinking-body illusion that could not be attributed to the effects of vibrating the wrist tendon or the position of the arms. This activity is given by the interaction term in the factorial design ([tendon contact – skin contact] – [tendon free – skin free]) (see Methods and Methods; Figure 1). We found one cluster of active voxels in the whole brain that was located in the left parietal lobe (size: 200 mm3; p < 0.05 corrected; see Figure 2). The cluster was located in the anterior part of the intraparietal sulcus and extended rostrally to the postcentral sulcus. This cluster contained two distinct peaks of activation (Figure 2). The anterior peak was located in the postcentral sulcus (x = −54, y = −30, z = 57 [x, y, and z coordinates in the standard space of the Montreal Neurological Institute]; t = 4.76; p < 0.001 uncorrected) near the junction of this sulcus and the intraparietal sulcus. The posterior peak was located at the border between the superior parietal convexity and the anterior part of intraparietal sulcus (x = −45, y = −39, z = 60; t = 3.86; p < 0.001 uncorrected). In the right hemisphere, there was a statistical trend for activation in the corresponding parietal sites (intraparietal sulcus: x = 42, −30, 60; t = 2.91; p = 0.005 uncorrected; superior parietal gyrus: x = 48, y = −33, z = 72; t = 3.15; p = 0.003; not shown in the Figures). The activity in the two left parietal foci was not significantly greater than the activity in the right corresponding areas (p > 0.19 uncorrected). Hence, the parietal cortex appears to be bilaterally engaged, albeit with only a statistical trend for activation on the right side.

Bottom Line: We found that activity in the cortices lining the left postcentral sulcus and the anterior part of the intraparietal sulcus reflected the illusion of waist shrinking, and that this activity was correlated with the reported degree of shrinking.These results suggest that the perceived changes in the size and shape of body parts are mediated by hierarchically higher-order somatosensory areas in the parietal cortex.Based on this finding we suggest that relative size of body parts is computed by the integration of more elementary somatic signals from different body segments.

View Article: PubMed Central - PubMed

Affiliation: Wellcome Department of Imaging Neuroscience, Institute of Neurology, London, United Kingdom. h.ehrsson@fil.ion.ucl.ac.uk

ABSTRACT
The perception of the size and shape of one's body (body image) is a fundamental aspect of how we experience ourselves. We studied the neural correlates underlying perceived changes in the relative size of body parts by using a perceptual illusion in which participants felt that their waist was shrinking. We scanned the brains of the participants using functional magnetic resonance imaging. We found that activity in the cortices lining the left postcentral sulcus and the anterior part of the intraparietal sulcus reflected the illusion of waist shrinking, and that this activity was correlated with the reported degree of shrinking. These results suggest that the perceived changes in the size and shape of body parts are mediated by hierarchically higher-order somatosensory areas in the parietal cortex. Based on this finding we suggest that relative size of body parts is computed by the integration of more elementary somatic signals from different body segments.

Show MeSH
Related in: MedlinePlus