The spatial metric representation of body parts: behavioural and neuropsychological evidence (original) (raw)
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The Quarterly Journal of Experimental Psychology Section A: Human Experimental Psychology
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A supramodal representation of the body surface
Neuropsychologia, 2011
The ability to accurately localize both tactile and painful sensations on the body is one of the most important functions of the somatosensory system. Most accounts of localization refer to the systematic spatial relation between skin receptors and cortical neurons. The topographic organization of somatosensory neurons in the brain provides a map of the sensory surface. However, systematic distortions in perceptual localization tasks suggest that localizing a somatosensory stimulus involves more than simply identifying specific active neural populations within a somatotopic map. Thus, perceptual localization may depend on both afferent inputs and other unknown factors. In four experiments, we investigated whether localization biases vary according to the specific skin regions and subset of afferent fibers stimulated. We represented localization errors as a 'perceptual map' of skin locations. We compared the perceptual maps of stimuli that activate Aβ (innocuous touch), Aδ (pinprick pain), and C fibers (non-painful heat) on both the hairy and glabrous skin of the left hand. Perceptual maps exhibited systematic distortions that strongly depended on the skin region stimulated. We found systematic distal and radial (i.e., towards the thumb) biases in localization of touch, pain, and heat on the hand dorsum. A less consistent proximal bias was found on the palm. These distortions were independent of the population of afferent fibers stimulated, and also independent of the response modality used to report localization. We argue that these biases are likely to have a central origin, and result from a supramodal representation of the body surface.
Using psychophysical tools to quantify body image perception: a tutorial
Motriz: Revista de Educação Física, 2015
This article presents a tutorial about two protocols that can be used to measure an individual's perception of body image, direct and indirect, and which follow S.S. Stevens (1951) methods. Two psychophysical task approaches illustrate the ability of individuals to quantify body image distortions. We selected psychophysical tasks that indirectly assess a participant's behavioral component of body image (i.e., satisfaction tendencies about body image); and second, the cognitive component of body image (i.e., individuals' perceptual accuracy in magnitude estimation tasks, which depend on a familiarity with interval scales and the use of numbers and ratios to represent physical dimensions of stimuli). We determined individuals' perceptual sensitivity (i.e., his or her perceptual style) to manipulations of the body's size by using Stevens' power function .
Proceedings of the Annual Meeting of the International Society For Psychophysics, 2014
Välkommen to the beautiful city of Lund in the province of Skåne, southern Sweden. It is an honor to host this year's 30th Annual Meeting of the International Society for Psychophysics (ISP) in Lund. Historically, Lund is one of the oldest cities in Sweden dating back to 990. Combining historic tradition with a young student population, Lund is a safe city with vibrant academic character, quaint cobble-stoned streets and, befitting of a young healthy population, bicycles. When Fechner presented his new transdisciplinary idea of "Psychophysik", he detailed a scientific method for studying relations between the physical and mental world of sensation and perception. Theoretical and methodological advance are still in focus today. This year, we are pleased to hear Hannes Eisler's tips from 55 years' research experience. In addition, the ISP and program committee are pleased to invite three speakers: Louis Narens, Simon Grondin, and Michael D. Lee. They are set to give stimulating talks on the scientific foundations of Stevens' power law, Weber fractions for time perception, and Bayesian methods for analyses of psychological models and data. We thank the Swedish Research Council ("Vetenskapsrådet") for providing funds to invite speakers from outside Sweden to this year's conference. Adding to the diversity of the meeting, three theme sessions are planned by Rosana Tristão, Leah Fostick, and Åke Hellström. These theme sessions focus on "what's new in pain perception", "individual differences in psychophysics", and "crossmodal and supramodal psychophysics". The welcome inclusion of these theme sessions promises to provide for lively discussion. Moreover, we have numerous fine free talks and posters related to the many aspects of psychophysical research. The presence of those directly concerned with the study of psychophysics, along with others who make use of psychophysical techniques, will ensure for a lively meeting of delegates at this year's Fechner Day conference. We thank the local city council for sponsoring the welcome reception. We also thank Jiří Wackermann, last year's conference organizer, for his invaluable help to get started and counsel. Also supporting the conference is Lund University who we thank for administrative support and for access to the university buildings situated, in splendid grounds, in the heart of Lund. We hope you enjoy the conference, stimulating intellectual discussions, and the relaxed ambience of Lund.
Specificity and coherence of body representations
Perception, 2009
Bodily illusions differently affect body representations underlying perception and action. We investigated whether this task dependence reflects two distinct dimensions of embodiment: the sense of agency and the sense of the body as a coherent whole. In experiment 1 the sense of agency was manipulated by comparing active versus passive movements during the induction phase in a video rubber hand illusion (vRHI) setup. After induction, proprioceptive biases were measured both by perceptual judgments of hand position, as well as by measuring end-point accuracy of subjects' active pointing movements to an external object with the affected hand. The results showed, first, that the vRHI is largely perceptual: passive perceptual localisation judgments were altered, but end-point accuracy of active pointing responses with the affected hand to an external object was unaffected. Second, within the perceptual judgments, there was a novel congruence effect, such that perceptual biases were larger following passive induction of vRHI than following active induction. There was a trend for the converse effect for pointing responses, with larger pointing bias following active induction. In experiment 2, we used the traditional RHI to investigate the coherence of body representation by synchronous stimulation of either matching or mismatching fingers on the rubber hand and the participant's own hand. Stimulation of matching fingers induced a local proprioceptive bias for only the stimulated finger, but did not affect the perceived shape of the hand as a whole. In contrast, stimulation of spatially mismatching fingers eliminated the RHI entirely. The present results show that (i) the sense of agency during illusion induction has specific effects, depending on whether we represent our body for perception or to guide action, and (ii) representations of specific body parts can be altered without affecting perception of the spatial configuration of the body as a whole.