Limits...
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.

Show MeSH

Related in: MedlinePlus

The Position of the Two Hands Relative to the Body and the Factorial Design of the ExperimentWhen the palms of the hands were in contact with the body, the vibration of the two wrists elicited the illusion that the wrists were passively flexing and the waist and hips were shrinking (A, lower right). When the hands were not in contact with the body, the vibration of the wrists only elicited the illusion that the hands were flexing (A, top right). In two additional conditions, we vibrated the skin over the styloid bone beside the tendon, which does not elicit any illusions (A, top left and lower left). The neural effect of the shrinking-body illusion can be modelled as the interaction term between hand position and site of vibration in a 2 × 2 factorial design (see [B], [tendon contact– skin contact] – [tendon free – skin free]).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC1287503&req=5

pbio-0030412-g001: The Position of the Two Hands Relative to the Body and the Factorial Design of the ExperimentWhen the palms of the hands were in contact with the body, the vibration of the two wrists elicited the illusion that the wrists were passively flexing and the waist and hips were shrinking (A, lower right). When the hands were not in contact with the body, the vibration of the wrists only elicited the illusion that the hands were flexing (A, top right). In two additional conditions, we vibrated the skin over the styloid bone beside the tendon, which does not elicit any illusions (A, top left and lower left). The neural effect of the shrinking-body illusion can be modelled as the interaction term between hand position and site of vibration in a 2 × 2 factorial design (see [B], [tendon contact– skin contact] – [tendon free – skin free]).

Mentions: Here we used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of perceptual changes of the size and shape of a body part. To experimentally manipulate the body image, we took advantage of a perceptual illusion—the “Pinocchio illusion” [4]—during which subjects feel that a body part changes its size and shape. This illusion has been demonstrated to work for both the length of the nose and for the width, height, and shape of various other body parts [4]. These illusions make use of the fact that vibration of the skin over the tendon of a joint extensor muscle elicits a vivid kinaesthetic illusion that the joint is passively flexing [17–21]. It is now well established that the illusory movements are caused by the excitation of muscle spindles in the vibrated muscle [18,22,23]. The afferent signals from this stimulation reach the primary somatosensory cortex [24–26] and primary motor cortex [19–21,26,27]. What Lackner [4] demonstrated was that if the hand is in direct contact with another body part, e.g., the nose or the waist, the subjects will not only feel that the vibrated wrist is bending but also experience the other body part being stretched or shrinking. In these situations the distortion of the body image is determined by the pattern of sensory stimulation according to a strict perceptual logic, so that the changes in shape and size of a body part appear to be caused by the illusory movement of the hand [4] (Protocol S1; Figures S1 and S2). For example, if the hand is grasping the nose and the biceps tendon is vibrated, one experiences the illusion that the hand is moving away from the face and the nose is becoming elongated. In contrast, when the triceps tendon is vibrated one feels that the hand is moving towards the face and that the nose is becoming shorter. We made use of the “waist-shrinking illusion.” The subjects put their hands so that the palms are in direct contact with the lateral sides of waist and the hips (see Figure 1). Then, when the tendons of the wrist extensor muscles are vibrated, the participants not only feel that the hands are bending inwards, but they also have the experience that the waist and the hips are shrinking.


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)

The Position of the Two Hands Relative to the Body and the Factorial Design of the ExperimentWhen the palms of the hands were in contact with the body, the vibration of the two wrists elicited the illusion that the wrists were passively flexing and the waist and hips were shrinking (A, lower right). When the hands were not in contact with the body, the vibration of the wrists only elicited the illusion that the hands were flexing (A, top right). In two additional conditions, we vibrated the skin over the styloid bone beside the tendon, which does not elicit any illusions (A, top left and lower left). The neural effect of the shrinking-body illusion can be modelled as the interaction term between hand position and site of vibration in a 2 × 2 factorial design (see [B], [tendon contact– skin contact] – [tendon free – skin free]).
© Copyright Policy
Related In: Results  -  Collection

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

pbio-0030412-g001: The Position of the Two Hands Relative to the Body and the Factorial Design of the ExperimentWhen the palms of the hands were in contact with the body, the vibration of the two wrists elicited the illusion that the wrists were passively flexing and the waist and hips were shrinking (A, lower right). When the hands were not in contact with the body, the vibration of the wrists only elicited the illusion that the hands were flexing (A, top right). In two additional conditions, we vibrated the skin over the styloid bone beside the tendon, which does not elicit any illusions (A, top left and lower left). The neural effect of the shrinking-body illusion can be modelled as the interaction term between hand position and site of vibration in a 2 × 2 factorial design (see [B], [tendon contact– skin contact] – [tendon free – skin free]).
Mentions: Here we used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of perceptual changes of the size and shape of a body part. To experimentally manipulate the body image, we took advantage of a perceptual illusion—the “Pinocchio illusion” [4]—during which subjects feel that a body part changes its size and shape. This illusion has been demonstrated to work for both the length of the nose and for the width, height, and shape of various other body parts [4]. These illusions make use of the fact that vibration of the skin over the tendon of a joint extensor muscle elicits a vivid kinaesthetic illusion that the joint is passively flexing [17–21]. It is now well established that the illusory movements are caused by the excitation of muscle spindles in the vibrated muscle [18,22,23]. The afferent signals from this stimulation reach the primary somatosensory cortex [24–26] and primary motor cortex [19–21,26,27]. What Lackner [4] demonstrated was that if the hand is in direct contact with another body part, e.g., the nose or the waist, the subjects will not only feel that the vibrated wrist is bending but also experience the other body part being stretched or shrinking. In these situations the distortion of the body image is determined by the pattern of sensory stimulation according to a strict perceptual logic, so that the changes in shape and size of a body part appear to be caused by the illusory movement of the hand [4] (Protocol S1; Figures S1 and S2). For example, if the hand is grasping the nose and the biceps tendon is vibrated, one experiences the illusion that the hand is moving away from the face and the nose is becoming elongated. In contrast, when the triceps tendon is vibrated one feels that the hand is moving towards the face and that the nose is becoming shorter. We made use of the “waist-shrinking illusion.” The subjects put their hands so that the palms are in direct contact with the lateral sides of waist and the hips (see Figure 1). Then, when the tendons of the wrist extensor muscles are vibrated, the participants not only feel that the hands are bending inwards, but they also have the experience that the waist and the hips are shrinking.

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