CT-optimal touch modulates proprioception and somatosensory-motor interaction: evidence for a vision-dependent mechanism

In this work participants completed a joint position-matching sense task by replicating two target angles (75°, 105°) with the elbow, measured with a universal goniometer. Participants performed three experimental conditions: (1) a baseline one, during which each angle was reproduced three times; (1) a CT-optimal condition, involving gentle brushing of the forearm at 3 cm/s; and (2) a CT-nonoptimal condition, in which the same brushing was delivered at 18 cm/s. In Experiment 1, sighted individuals participated in the study. In this case the conditions were divided in two sessions, in the first one took place the baseline condition, while the tactile conditions were performed 24 hours later. In Experiment two blind participants took part on the experiment, performing all conditions in a single session.

The angle perceived was registered and the difference between the real and the perceived one computed.

“participant” is the code of each participant. “age” is the age of each participant, “condition” is whether the condition was the baseline (bs), CT-optimal touch (aff), or CT-nonoptimal touch (nonaff), “angle” is the two angles participants had to match (i.e. 105° or 75°), “pleasantness” is the rated pleasantness in the tactile conditions, “angle_perceived” is the angle perceived by the participant, “diff_angles” is the difference between the real angle and the perceived one. In Experiment 2, is also included “group”, in which EB represents early blind participants, while “LB” represents late blind individuals, “blindness_onset” constitute the age in which the participant reported complete blindness.