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Proprioceptive body illusions modulate the visual perception of reaching distance.

Petroni A, Carbajal MJ, Sigman M - PLoS ONE (2015)

Bottom Line: Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement.Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect.Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Física, FCEN-UBA, Ciudad Universitaria, (1428) Buenos Aires, Argentina.

ABSTRACT
The neurobiology of reaching has been extensively studied in human and non-human primates. However, the mechanisms that allow a subject to decide-without engaging in explicit action-whether an object is reachable are not fully understood. Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement. Others have shown that the body schema plays a role in explicit and implicit distance estimation, especially after motor practice with a tool. In this study we evaluate the causal role of multisensory body representations in the perception of reachable space. We reasoned that if body schema is used to estimate reach, an illusion of the finger size induced by proprioceptive stimulation should propagate to the perception of reaching distances. To test this hypothesis we induced a proprioceptive illusion of extension or shrinkage of the right index finger while participants judged a series of LEDs as reachable or non-reachable without actual movement. Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect. Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.

No MeSH data available.


Related in: MedlinePlus

Finger size change report vs Delta Threshold and Delta RT.(a) Linear regression of subjective finger size change on reaching threshold shift. (b) Linear regression of subjective finger size change on reaction time peak shift. In both plots the regression line and 95% confidence intervals are depicted in black and dashed black lines, respectively. Identity line (y = x) is depicted in red.
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pone.0131087.g004: Finger size change report vs Delta Threshold and Delta RT.(a) Linear regression of subjective finger size change on reaching threshold shift. (b) Linear regression of subjective finger size change on reaction time peak shift. In both plots the regression line and 95% confidence intervals are depicted in black and dashed black lines, respectively. Identity line (y = x) is depicted in red.

Mentions: If judgments of reach are based on body representations, those participants perceiving a greater extension of their reach region should also feel a greater illusion. Similarly, the RT distribution should also shift revealing greater RTs close to the displaced threshold. To examine these predictions, we performed a linear regression of the reported illusion RI(s) to ΔT(s) and ΔRT(s) where s indicates the measure for each specific subject (Fig 4). The regression of subjective illusion reports on T yielded a significant slope βΔT = 0.85 (p < 0.005, f = 14.26, df = 18). The regression of subjective illusion reports on RT yielded a significant slope βΔRT = 0.88 (p < 0.001, f = 16.12, df = 18). Both regression slopes overlap with the identity line within the 95% confidence interval of the regression slope. Thus, increases in the estimated reach threshold result in proportional -with a proportion coefficient not different from 1- increases in the perceived illusion.


Proprioceptive body illusions modulate the visual perception of reaching distance.

Petroni A, Carbajal MJ, Sigman M - PLoS ONE (2015)

Finger size change report vs Delta Threshold and Delta RT.(a) Linear regression of subjective finger size change on reaching threshold shift. (b) Linear regression of subjective finger size change on reaction time peak shift. In both plots the regression line and 95% confidence intervals are depicted in black and dashed black lines, respectively. Identity line (y = x) is depicted in red.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4482541&req=5

pone.0131087.g004: Finger size change report vs Delta Threshold and Delta RT.(a) Linear regression of subjective finger size change on reaching threshold shift. (b) Linear regression of subjective finger size change on reaction time peak shift. In both plots the regression line and 95% confidence intervals are depicted in black and dashed black lines, respectively. Identity line (y = x) is depicted in red.
Mentions: If judgments of reach are based on body representations, those participants perceiving a greater extension of their reach region should also feel a greater illusion. Similarly, the RT distribution should also shift revealing greater RTs close to the displaced threshold. To examine these predictions, we performed a linear regression of the reported illusion RI(s) to ΔT(s) and ΔRT(s) where s indicates the measure for each specific subject (Fig 4). The regression of subjective illusion reports on T yielded a significant slope βΔT = 0.85 (p < 0.005, f = 14.26, df = 18). The regression of subjective illusion reports on RT yielded a significant slope βΔRT = 0.88 (p < 0.001, f = 16.12, df = 18). Both regression slopes overlap with the identity line within the 95% confidence interval of the regression slope. Thus, increases in the estimated reach threshold result in proportional -with a proportion coefficient not different from 1- increases in the perceived illusion.

Bottom Line: Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement.Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect.Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Física, FCEN-UBA, Ciudad Universitaria, (1428) Buenos Aires, Argentina.

ABSTRACT
The neurobiology of reaching has been extensively studied in human and non-human primates. However, the mechanisms that allow a subject to decide-without engaging in explicit action-whether an object is reachable are not fully understood. Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement. Others have shown that the body schema plays a role in explicit and implicit distance estimation, especially after motor practice with a tool. In this study we evaluate the causal role of multisensory body representations in the perception of reachable space. We reasoned that if body schema is used to estimate reach, an illusion of the finger size induced by proprioceptive stimulation should propagate to the perception of reaching distances. To test this hypothesis we induced a proprioceptive illusion of extension or shrinkage of the right index finger while participants judged a series of LEDs as reachable or non-reachable without actual movement. Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect. Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas.

No MeSH data available.


Related in: MedlinePlus