Gating of spontaneous somatic sensations by movement

Abstract

Movement is known to attenuate the perception of tactile stimuli delivered on the moving part of the body, and this gating diminishes the greater the distance from the moving part. However, does it influence the perception of sensations occurring spontaneously without external triggers? In Experiment 1, participants were asked to focus on one hand while moving or not moving their thumb, and thereafter to map and describe the spatial and qualitative attributes of sensations perceived over the remaining, motionless part of the hand. The results show that movement reduces the frequency, spatial extent, and intensity of sensations, but also participants’ confidence about their spatial characteristics. As expected, gating decreased the greater the distance from the moving thumb. Furthermore, gating was greater for distal than proximal segments of the hand, suggesting a hierarchical proximo-distal suppression. Experiment 2 ruled out the possibility that these effects were due to tactile sensations elicited by movement. Possible mechanisms of gating in the case of spontaneous sensations are discussed.

• Hands
• interoception
• movement
• sensory gating
• spontaneous sensations
• tactile perception

Acknowledgements

We would like to express our gratitude to Madeline Mechin for her valuable help in collecting some of the data presented here. This work was supported by the LABEX CORTEX (ANR-11-LABX-0042) of Université de Lyon, within the program “Investissements d’Avenir” (ANR-11-IDEX-0007) operated by the French National Research Agency (ANR).

Notes

1. Paired proportions can be compared using Liddell’s exact test (Liddell 1983), which is preferable to the more classically used McNemar’s chi-squared test because it overrides the requirements of minimal cell values and minimal number of participants. Liddell’s exact test is a special case of the sign test. The b count in a 2 × 2 table is treated as a binomial variable from the sample b + c, where b represents the present–absent cell and c the absent–present cell. Test statistic F = b/(c + 1) and it follows the Fischer distribution with n and d degrees of freedom, n being the total number of observations and d being the absent–absent cell. In this study, F-values were calculated for each individual cell during comparisons of two binary maps.

2. A more global analysis of variance taking into account both the fingers and anatomical segments could not be performed because it is not possible to divide the palm into sub-segments equivalent to the phalanges.