A three-dimensional spatial characterization of the crossed-hands deficit

Abstract

To perceive the location of touch in space, we integrate information about skin-location with information about the location of that body part in space. Most research investigating this process of tactile spatial remapping has used the so-called crossed-hands deficit, in which the ability to judge the temporal order of touches on the two hands is impaired when the arms are crossed. This posture induces a conflict between skin-based and tactile external spatial representations, specifically in the left-right dimension. Thus, it is unknown whether touch is affected by posture when spatial relations other than the right-left dimension are available. Here, we tested the extent to which the crossed-hands deficit is a measure of tactile remapping, reflecting tactile encoding in continuous three-dimensional space. Participants judged the temporal order of tactile stimuli presented to crossed and uncrossed hands. The arms were placed at different elevations (up-down dimension; Experiments 1 and 2), or at different distances from the body in the depth plane (nearfar dimension; Experiment 3). The crossed-hands deficit was reduced when other sources of spatial information, orthogonal to the left-right dimension, were available. Nonetheless, the deficit persisted in all conditions, even when processing of non-conflicting information was enough to solve the task. Together, these results demonstrate that the processing underlying the crossed-hands deficit is related to the encoding of tactile localization in three-dimensional space, rather than related uniquely to the cost of processing information in the right-left dimension. Furthermore, the persistence of the crossing effect provides evidence for automatic integration of all available information, regardless of whether or not it is conflicting.3

The Sensitive Period for Tactile Remapping Does Not Include Early Infancy

“…In Figure , we compared performance of LM in the two postures with that of 343 participants from 12 published studies (Azañón et al., ; Azañón, Mihaljevic, et al., ; Azañón, Radulova, et al., ; Azañón & Soto‐Faraco, ; Badde et al., , ; Ley et al., ; Nishikawa et al., ; Roberts & Humphreys, ; Schicke & Röder, ; Wada et al., ; Yamamoto & Kitazawa, ) and two unpublished studies tested in similar bimanual crossed‐hand TOJ paradigms. LM's performance in the crossed‐hands posture was in the top 2–3% of the population (with a percentile of 98 and 97, for probit slopes and accuracy, respectively).…”

“…We investigated whether the use of an automatic remapping of touch into an external reference frame requires visual input during the first months of life. Extensive previous research has shown that normally sighted humans localize touch into external coordinates automatically (Yamamoto & Kitazawa, 2001;Azañ on, Camacho, & Soto-Faraco, 2010;Kitazawa, 2002). Here, we tested the spatial remapping of touch in a group of children who were born with cataracts and were, thus, deprived of vision for the first months of life (up to 5 months of age).…”

“…Data were taken with permission from 12 published studies and 2 unpublished studies that tested similar bimanual TOJ paradigms with crossed and uncrossed arms (corresponding to 22 experiments). Published data (included in parentheses are the names of the experiments and conditions): first study (Yamamoto & Kitazawa, ; main TOJ task): n = 20; second study (Wada, Yamamoto, & Kitazawa, ; left‐ and right‐handed groups): n = 32; third study (Schicke & Röder, ; hands‐only condition): n = 10; fourth study (Azañón & Soto‐Faraco, ; Experiments 1 and 2 ‐ congruent conditions only): n = 39; fifth study (Roberts & Humphreys, ; Experiments 1 and 2): n = 18; sixth study (Ley et al., ; controls for patient HS in Experiment 1): n = 5; seventh study (Badde et al., ; Experiment 2‐TOJ single task): n = 17; eighth study (Badde et al., ; TOJ task): n = 19; ninth study (Azañón, Stenner, Cardini, & Haggard, ; Experiment 1‐continuous condition): n = 12; 10th study (Nishikawa, Shimo, Wada, Hattori, & Kitazawa, ; young and elderly groups, participants that were tested both in the crossed and uncrossed conditions only): n = 41; 11th study (Azañón, Radulova, Haggard, & Longo, ; Experiments 1 and 4‐finger conditions): n = 29, 12th study (Azañón, Mihaljevic, & Longo, ; Experiments 1 , 2, and 3 ‐ aligned conditions only): n = 48. The unpublished data correspond to data of 39 participants (from currently two unpublished studies from our laboratory) plus the 14 controls for LM in this study.…”

“…This crossed-hands deficit has been interpreted as reflecting the automatic remapping of touch into external coordinates. Because posture is irrelevant to the task (i.e., the use of somatotopic coordinates alone is, in principle, enough to solve the task), the deficit suggests that tactile processing takes into account postural information by default, even in situations in which this is detrimental to performing the task (Azañ on, Camacho, & Soto-Faraco, 2010;Kitazawa, 2002).…”

Bodily awareness and novel multisensory features

“…In other words, tactual attention can be directed to locations that are represented in a frame of reference that isn't somatotopic and, so, could potentially be used to also represent the locations of objects that are seen or heard. A similar conclusion can be extracted from experimental studies of the so-called "crossed-hands deficit", in which a subject's ability to judge the temporal order of tactile stimuli presented to her hands is impaired when her arms are crossed (Yamamoto and Kitazawa 2001;Shore and Spence 2002;Heed et al 2012;Azañón et al 2016).…”