DOI: 10.5061/dryad.t4b8gtj9d
title: Data from: Repetitive somatosensory stimulation shrinks the body image

description: Current models of mental body representations (MBRs) indicate that tactile
 inputs feed some of them for different functions, implying that altering
 tactile inputs may affect MBRs differently. Here we tested this hypothesis
 by leveraging Repetitive Somatosensory Stimulation (RSS), known to improve
 tactile perception by modulating primary somatosensory cortex (SI)
 activity, and measured its effects over the body image, the body model and
 the superficial schema in a randomized sham-controlled, double-blind
 cross-over study. Results show that RSS affected the body image,
 participants perceiving their finger size as being smaller after RSS.
 While previous work showed increase of finger size perception after
 tactile anesthesia, these findings reveal that tactile inputs can
 diametrically modulate the body image. In contrast, RSS did not seem to
 alter the body model or superficial schema. In addition, we report a novel
 mislocalization pattern, with a bias towards the middle finger in the
 distal phalanges that reverses towards the thumb in the proximal phalanx,
 enriching the known distortions of the superficial schema. Overall, these
 findings provide novel insights into the functional organization of MBRs
 and their relationships with somatosensory information. Reducing the
 perceived body size through RSS could be useful in helping treat body
 image disturbances.
description: # Data from: Repetitive somatosensory stimulation shrinks the body image
 [https://doi.org/10.5061/dryad.t4b8gtj9d](https://doi.org/10.5061/dryad.t4b8gtj9d) In this randomized sham-controlled, double-blind cross-over study, we assessed the effects of Repetitive Somatosensory Stimulation (RSS; known to improve tactile perception through a modulation of primary somatosensory cortex activity) on three mental body representations (MBRs): the body image, the body model and the superficial schema. With a within-subject design (each subject received RSS and Sham on separate days), three tasks were used to assess these MBRs before and after the RSS or Sham stimulation: the template matching task (TMT; body image), the tactile distance judgement task (TDJT; body model & superficial schema) and the tactile localization task (TLT; superficial schema). Tactile perception was also assessed to check for RSS efficacy through the two-point discrimination task (2PDT). ## Description of the data and file structure **2PDT_LMM.xlsx**: contains the discrimination thresholds (PSEs) in mm obtained before (Pre) and after (Post) each intervention (Sham / RSS). **2PDT_S1S2.csv**: contains the discrimination thresholds (PSEs) in mm obtained in each baseline session S1 and S2 before the intervention (Sham / RSS). **TMT_LMM.xlsx**: contains the distortion thresholds (PSEs) in % (of image distortion) obtained before (Pre) and after (Post) each intervention (Sham / RSS). **TDJT_LMM_byTrials.xlsx**: contains the perceived distances in mm obtained before (Pre) and after (Post) each intervention (Sham / RSS) in each position (Tip, Base) and distance (15 mm, 30 mm). **TDJT_LMM_byTrials_withoutOutliers.xlsx**: same as "TDJT_LMM_byTrials.xlsx" without outliers. **TLT_Vector_LMM.xlsx**: contains the constant error magnitude in mm (euclidean distance between the judged and real locations) obtained before (Pre) and after (Post) each intervention (Sham / RSS) in each phalanx (Proximal (P), Middle (M), Distal (D)) and point (Proximal (1), Middle (2), Distal (3)) --&gt; e.g. "Pre P1" refers to the proximal point of the proximal phalanx before the intervention. **TLT_Vector_LMM_withoutOutliers.xlsx**: same as "TLT_Vector_LMM.xlsx" without outliers. **TLT_ConstantErrorDirection.csv**: contains the constant error direction in degrees (angle between the Judged-Real vector and x-axis) obtained before (Pre) and after (Post) each intervention (Sham / RSS) in each phalanx (Proximal (P), Middle (M), Distal (D)) and point (Proximal (1), Middle (2), Distal (3)). **TLT_CEdirection**_**HarrisonKanji.xlsx**: Same data as in "TLTConstantErrorDirection.csv", arranged for the Harrison-Kanji test (two-way ANOVA for circular data) --&gt; Each sheet contains data for one point. The 1st column contains the direction data (in degrees), the 2nd contains the Intervention (1= Sham; 2= RSS), and the 3rd contains the Session (1= Pre; 2= Post). **TLT_CEdirection**_**HarrisonKanji.m**: this Matlab script reads "TLT_CEdirection_HarrisonKanji.xlsx" and is used to perform the Harrison-Kanji test for each point (P1, P2, P3, M1, M2, M3, D1, D2, D3). --&gt; the output files ("HarrisonKanji_P1.txt" etc.) contain the results of the test. The results consist in either the X² statistic or the F: In the Harrison-Kanji test, when the pooled sample concentration parameter κ&gt;2, the appropriate statistic is the F, while when κ&lt;2, it is the X² (see Harrison & Kanji, 1988 for details). **TLT_Ellipse_LMM.xlsx**: contains the variable errors in mm² (the areas of the 95%-confidence ellipses) obtained before (Pre) and after (Post) each intervention (Sham / RSS) in each phalanx (Proximal (P), Middle (M), Distal (D)) and point (Proximal (1), Middle (2), Distal (3)). **TLT_Ellipse_LMM_withoutOutliers.xlsx**: same as "TLT_Ellipse_LMM.xlsx" without outliers. **ellipse_generator.m**: this Matlab script is used to build the 95%-confidence ellipses and compute their parameters for each subject (at each point in each condition). --&gt; the output file "parameters.xlsx" for each subject displays the parameters for each condition in the following order (from left to right): PreSham, PostSham, PreRSS, PostRSS. **error_ellipse_function.m**: this function is called by the "ellipse_generator.m" script and allows to compute the ellipse parameters. **Coordinates.csv**: this csv file containing the x and y coordinates (obtained after normalizing the raw coordinates to each subject's finger size) is the input file used by the "ellipse_generator.m" script. Caution: it should be converted back to ".xlsx" to be read by the script. **LMM_2PDT.R**: this R script is used to apply Linear mixed-effects models (LMMs) to the 2PDT data. **LMM_TMT.R**: this R script is used to apply Linear mixed-effects models (LMMs) to the TMT data. **LMM_TDJT.R**: this R script is used to apply Linear mixed-effects models (LMMs) to the TDJT data. **LMM_TLT_Ellipse.R**: this R script is used to apply Linear mixed-effects models (LMMs) to the variable error of the TLT data. **LMM_TLT_Vector.R**: this R script is used to apply Linear mixed-effects models (LMMs) to the constant error magnitude of the TLT data. ## Softwares The Matlab scripts used to compute the 95%-confidence ellipses parameters (ellipse_generator.m) and to perform the Harrison-Kanji test (TLT_CEdirection_HarrisonKanji.m) were run on Matlab 2021b. The statistical analyses were run on RStudio (v2024.12.0). ## Human subjects data We received explicit consent from the participants to publish de-identified data in the public domain. In the datasets, numbers were attributed to the participants. They are thus referred to as "Subject number ...".