Posture modulates implicit hand maps

Quarterly Journal of Experimental Psychology

2017

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Delusions and misperceptions about the body are a conspicuous feature of numerous neurological and psychiatric conditions. In stark contrast to such pathological cases, the immediacy and familiarity of our ordinary experience of our body can make it seem as if our representation of our body is highly accurate, even infallible. Recent research has begun to demonstrate, however, that large and systematic distortions of body representation are a normal part of healthy cognition. Here, I will describe this research, focusing on distortions of body representations underlying tactile distance perception and position sense. I will also discuss evidence for distortions of higherorder body representations, such as the conscious body image. Finally, I will end with a discussion of the potential relations among different body representations and their distortions. Distortions of Body Representations 3Our body is the core of our sense of self, and central to our personal identity as an individual. We experience our body from the outside, as a physical object in the world like any other, but also from the inside, as an object of immediate experience (Bermúdez, Marcel, & Eilan, 1995). The intimate and direct connection we have with our own body can make knowledge of our body seem immune to the usual sources of perceptual error and illusion. Indeed, the very fact that we have multiple ways of knowing about our body (from inside, and from outside) could very well contribute to making the overall perception of the body highly reliable. While distortions and misperceptions of the body are a familiar result of several psychiatric and neurological conditions, it is natural to suppose that healthy adults have highly accurate -even infallible -knowledge about the physical structure of their bodies. In this paper, I will describe recent research that has begun to question this assumption, showing large and systematic distortions of body representation in healthy adults. After giving a brief summary of the varied distortions of body representation found in pathological conditions, I will describe research showing large distortions of body representations

Section: Distortions In Position Sensementioning

confidence: 55%

Distorted Body Representations in Healthy Cognition

Quarterly Journal of Experimental Psychology

2017

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“…Subsequent studies have replicated this general pattern, showing that perceived tactile distances appear to be systematically related to the sensitivity of different skin surfaces (e.g., Goudge, 1918; Marks et al, 1982; Cholewiak, 1999; Taylor-Clarke et al, 2004; Anema et al, 2008; Miller et al, 2016). Similarly, large anisotropies of perceived tactile distance have been reported on the limbs, with stimuli oriented across the width of limbs being perceived as substantially farther apart than stimuli oriented along the length of the limbs (Green, 1982; Longo and Haggard, 2011; Canzoneri et al, 2013; Longo and Sadibolova, 2013; Le Cornu Knight et al, 2014; Miller et al, 2014, 2016; Longo, 2015). For example, in the study of Longo and Haggard (2011), we presented participants sequentially with two pairs of touches on each trial, one pair oriented along the proximo-distal axis of their hand and the other oriented with the medio-lateral axis.…”

Section: Introductionmentioning

confidence: 91%

“…By comparing the relative locations of judgments of each landmark, an implicit perceptual map of the hand can be constructed and compared to the actual form of the hand. Studies using this paradigm have revealed a fat, squat hand representation, with overestimation of hand width and underestimation of finger length (e.g., Longo and Haggard, 2010, 2012a,b; Lopez et al, 2012; Ferrè et al, 2013; Longo, 2014, 2015; Mattioni and Longo, 2014; Coelho et al, 2016; Saulton et al, 2016). …”

Section: Introductionmentioning

confidence: 99%

No Correlation between Distorted Body Representations Underlying Tactile Distance Perception and Position Sense

Morcom

2016

Front. Hum. Neurosci.

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Both tactile distance perception and position sense are believed to require that immediate afferent signals be referenced to a stored representation of body size and shape (the body model). For both of these abilities, recent studies have reported that the stored body representations involved are highly distorted, at least in the case of the hand, with the hand dorsum represented as wider and squatter than it actually is. Here, we investigated whether individual differences in the magnitude of these distortions are shared between tactile distance perception and position sense, as would be predicted by the hypothesis that a single distorted body model underlies both tasks. We used established tasks to measure distortions of the represented shape of the hand dorsum. Consistent with previous results, in both cases there were clear biases to overestimate distances oriented along the medio-lateral axis of the hand compared to the proximo-distal axis. Moreover, within each task there were clear split-half correlations, demonstrating that both tasks show consistent individual differences. Critically, however, there was no correlation between the magnitudes of distortion in the two tasks. This casts doubt on the proposal that a common body model underlies both tactile distance perception and position sense.

“…This overall pattern has been replicated numerous times in several labs (Cocchini et al in press;Coelho et al 2017;Coelho and Gonzalez in press;Ferrè et al 2012;Ganea and Longo 2017;Longo 2014Longo , 2015Longo , 2017bHaggard 2012a, 2012b;Longo et Response Type and Perceptual Hand Maps 4 al. 2012, 2015a, 2015bLongo and Morcom 2016;Lopez et al 2012;Mattioni and Longo 2014;Medina and Duckett 2017;Saulton et al 2015Saulton et al , 2016Saulton et al , 2017Stone et al 2018;Tamè et al 2017). Nevertheless, the interpretation of such effects remains uncertain.…”

Section: Introductionmentioning

confidence: 99%

“…While my colleagues and I have interpreted these distortions as reflecting a central body model (e.g., Azañón et al 2016;Longo 2017a;Longo et al 2015a), some researchers have proposed that they may result from more general perceptual and motor processes (Medina and Duckett 2017;Saulton et al 2015Saulton et al , 2016Saulton et al , 2017.…”

Section: Introductionmentioning

confidence: 99%

The effects of instrumental action on perceptual hand maps

2018

Exp Brain Res

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Perceiving the external spatial location of body parts using position sense requires that immediate proprioceptive afferent signals be integrated with information about body size and shape. Longo and Haggard (Proc Natl Acad Sci 107:11727-11732, 2010) developed a method to measure perceptual hand maps reflecting this metric information about body size and shape. In this paradigm, participants indicate the perceived location of landmarks on their occluded hand by pointing with a long baton held in their other hand. By comparing the relative location of judgments of different hand landmarks, perceptual hand maps can be constructed and compared to actual hand structure. The maps show large and highly stereotyped distortions. Here, I investigated the potential effect of biases related to active motor control of the hand doing the pointing in these distortions. Participants localized the fingertip and knuckle of each finger on their occluded left hand either by actively pointing with a baton held in their right hand (pointing condition) or by giving verbal commands to an experimenter on how to move the baton (verbal condition). Similar distortions were clearly apparent in both conditions, suggesting that they are not an artifact of motor control biases related to the pointing hand.