Adaptation aftereffects reveal that tactile distance is a basic somatosensory feature

Calzolari, Elena; Azañón, Elena; Danvers, Matthew; Vallar, Giuseppe; Longo, Matthew R.

doi:10.1073/pnas.1614979114

Cited by 46 publications

(74 citation statements)

References 62 publications

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“…1a,b). Because low-level skin maps are thought to be anatomically organized (26), common external-spatial error across the two postures would indicate motor error of the pointing hand rather than perceptual localization error on the target arm. Participants reached, with their eyes closed, using their right index finger to the left forearm, touched down, and then moved their finger across the skin until they felt to have reached the target.…”

Section: Resultsmentioning

confidence: 99%

Online sensory feedback during active search improves tactile localization

Fuchs

Wulff

Heed

2019

Preprint

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AbstractMany natural behaviors involve closed feedback loops in which ongoing sensory input refines motor behavior. Previous research on tactile localization, however, has implemented localization as open-loop behavior. For instance, participants indicate a touched position on a silhouette shape of the body or on an occluding board mounted above the hand. Such studies have suggested that humans often make large errors when localizing touch on the skin, or that “perceptual body representations” are distorted. However, by artificially preventing tactile feedback from the target body area, the natural action-perception loop is interrupted. Therefore, these localization approaches may underestimate individuals’ localization ability and draw erroneous conclusions about the role and precision of body representations. Here, we tested tactile localization in a natural setting, in which participants first received brief touches on their left forearm and then searched for the target location by moving the right index finger across the skin. Tactile search reduced localization error when the searching finger was far from, but not when it was near the target, resulting in a remaining error of 1-2 cm. Error reduction was absent when participants searched on an acrylic barrier mounted above the arm, suggesting that availability of tactile feedback on the target arm but not proprioceptive and motor signals of the searching arm determined precision, thus confirming the pivotal role of closed-loop sensory feedback for tactile localization. We suggest that actively produced online tactile feedback routinely refines coarse spatial body representations, similar to the refinement of sparse spatial representations in visual memory through consecutive saccades.

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Section: Resultsmentioning

confidence: 99%

Online sensory feedback during active search improves tactile localization

Fuchs

Wulff

Heed

2019

Preprint

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“…On one model, perceived distance may be a relatively direct readout of the structure of tactile 42 space as coded by body maps in early somatosensory cortex. This interpretation is supported 43 by the fact that tactile distance adaptation aftereffects show low-level characteristics such as 44 orientation-and location-specificity (Calzolari et al, 2017), as well as by the relation between 45 tactile distance illusions and factors such as cortical magnification and RF geometry. In this 46 case, the representation of the body (i.e., hand) in SI should mirror the distortions observed 47 perceptually.…”

Section: Introductionmentioning

confidence: 95%

“…Since the pioneering work of Weber (1834Weber ( /1996, the perception of tactile distance 3 has been widely used to investigate the somatosensory system and its links to higher-level 4 aspects of body representation. Recent results have shown that tactile distance is susceptible 5 to sensory adaptation (Calzolari, Azañón, Danvers, Vallar, & Longo, 2017), suggesting that it 6 might be a basic feature coded at relatively early stages of somatosensory processing. Indeed,7 there is evidence that perceived tactile distance is shaped by low-level features of 8 somatosensory organization such as cortical magnification (Cholewiak, 1999;Taylor-Clarke, 9 Jacobsen, & Haggard, 2004;Weber, 1834Weber, /1996 and receptive field (RF) geometry (Brown, 10 Fuchs, & Tapper, 1975;DiCarlo, Johnson, & Hsiao, 1998).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing neural representations of tactile space

Tamè

Tucciarelli

Sadibolova

et al. 2019

Preprint

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Psychophysical experiments have demonstrated large and highly systematic perceptual distortions of tactile space. We investigated the neural basis of tactile space by analyzing activity patterns induced by tactile stimulation of nine points on a 3 x 3 square grid on the hand dorsum using functional magnetic resonance (fMRI). We used a searchlight approach within pre-defined regions of interests (ROIs) to compute the pairwise Euclidean distances between the activity patterns elicited by tactile stimulation. Then, we used multidimensional scaling (MDS) to reconstruct tactile space at the neural level and compare it with skin space at the perceptual level. Our reconstructions of the shape of skin space in contralateral primary somatosensory (SI) and motor (M1) cortices reveal that it is distorted in a way that matches the perceptual shape of skin space. This suggests that early sensorimotor areas are critical to processing tactile space perception. Significant StatementHere, we show that the primary somatosensory (SI) and motor (M1) cortices, rather than higher-level brain areas, are critical to estimating distances between tactile stimuli on the hand dorsum. By combining functional magnetic resonance (fMRI), Procrustes alignment, and multidimensional scaling, we reconstructed the shape of skin space in the brain. Strikingly, the shape of the skin that we reconstructed from neural data matches the distortions we found at the behavioral level, providing strong evidence that early sensorimotor areas are critical for the construction of tactile space. Our work therefore supports the view that tactile distance perception is computed at lower level in the somatosensory system than is usually supposed.

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“…The stimuli were wooden sticks which tapered to a point (~1mm) but were not sharp, similar to those we have used in previous studies 13 , 16 , 19 , 29 , 63 , 64 . Pairs of sticks were mounted in foamboard, separated by 20, 30, or 40 mm.…”

Section: Experiments 1 – Forced-choice Judgmentsmentioning

confidence: 99%

Hand Posture Modulates Perceived Tactile Distance

Longo¹

2017

Sci Rep

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A growing literature shows that body posture modulates the perception of touch, as well as somatosensory processing more widely. In this study, I investigated the effects of changes in the internal postural configuration of the hand on the perceived distance between touches. In two experiments participants positioned their hand in two postures, with the fingers splayed (Apart posture) or pressed together (Together posture). In Experiment 1, participants made forced-choice judgments of which of two tactile distances felt bigger, one oriented with the proximal-distal hand axis (Along orientation) and one oriented with the medio-lateral hand axis (Across orientation). In Experiment 2, participants made verbal estimates of the absolute distance between a single pair of touches, in one of the two orientations. Consistent with previous results, there was a clear bias to perceive distances in the across orientation as larger than those in the along orientation. Perceived tactile distance was also modulated by posture, with increased judgments in both orientations when the fingers were splayed. These results show that changes in the internal posture of the hand modulate the perceived distance between touches on the hand, and add to a growing literature showing postural modulation of touch.

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Adaptation aftereffects reveal that tactile distance is a basic somatosensory feature

Cited by 46 publications

References 62 publications

Online sensory feedback during active search improves tactile localization

Online sensory feedback during active search improves tactile localization

Reconstructing neural representations of tactile space

Hand Posture Modulates Perceived Tactile Distance

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