Tactile spatial discrimination on the torso using vibrotactile and force stimulation

Abstract

There is a steadily growing number of mobile communication systems that provide spatially encoded tactile information to the humans’ torso. However, the increased use of such hands-off displays is currently not matched with or supported by systematic perceptual characterization of tactile spatial discrimination on the torso. Furthermore, there are currently no data testing spatial discrimination for dynamic force stimuli applied to the torso. In the present study, we measured tactile point localization (LOC) and tactile direction discrimination (DIR) on the thoracic spine using two unisex torso-worn tactile vests realized with arrays of 3 × 3 vibrotactile or force feedback actuators. We aimed to, first, evaluate and compare the spatial discrimination of vibrotactile and force stimulations on the thoracic spine and, second, to investigate the relationship between the LOC and DIR results across stimulations. Thirty-four healthy participants performed both tasks with both vests. Tactile accuracies for vibrotactile and force stimulations were 60.7% and 54.6% for the LOC task; 71.0% and 67.7% for the DIR task, respectively. Performance correlated positively with both stimulations, although accuracies were higher for the vibrotactile than for the force stimulation across tasks, arguably due to specific properties of vibrotactile stimulations. We observed comparable directional anisotropies in the LOC results for both stimulations; however, anisotropies in the DIR task were only observed with vibrotactile stimulations. We discuss our findings with respect to tactile perception research as well as their implications for the design of high-resolution torso-mounted tactile displays for spatial cueing.

Encoding of spatial patterns using electrotactile stimulation via a multi‐pad electrode placed on the torso

“…Hoffmann and collaborators 38 reported a higher tactile acuity along the horizontal axis at the lower back skin area using vibrotactile stimulation. Comparable findings were reported by Jouybari and co‐workers 32 for vibrotactile stimulations but not for focal forces where participants performed better in identifying stimuli aligned horizontally compared to vertically at the top back area of the torso. Similarly to the present findings, Štrbac and colleagues 17 reported less confusion between the spatial identification of the electrodes along the horizontal axis compared to the vertical axis, when using electrotactile stimulation at the lateral torso.…”

“…31 Transmitting information through tactile stimulation delivered to the torso or the base of the neck, results in active body segments (e.g., upper and lower limbs) being fully available for other activities. [2][3][4][5][6][31][32][33][34] Therefore, the present study assessed the participants' aptitude to perceive and recognize tactile messages rendered in the form of spatial patterns using a 3 × 2 pad matrix placed on the lateral torso. The preliminary results of this study were published as a conference contribution.…”

“…In recent years, wearable tactile devices placed on the torso have gained attention 31 . Transmitting information through tactile stimulation delivered to the torso or the base of the neck, results in active body segments (e.g., upper and lower limbs) being fully available for other activities 2–6,31–34 …”

Remapping of stance-phase tactile foot sensation to the back modulates locomotor perception with limited adaptation

“…We adapted previous paradigms for conscious gait monitoring via auditory [42] and visual [44] cues to touch feedback during walking. This wearable, untethered tactile remapping system allowed us to introduce a specific range of temporal delays between participants' actual, on-going footsteps and step-related tactile cues provided onto the skin of their back [10], [11]. We hypothesised to observe systematic modulation in MA depending on the delay, with strongest MA ratings for both real-time feedback, as well as feedback delayed for the duration of the participants gait-cycle (resynchronised feedback).…”

“…Accordingly, one motivating factor for this study was to determine to what extent sensorimotor feedback is perceived as selfgenerated and how this affects motor behaviour (adaptation). Based on our prior work on haptic vests [10], [11], we here developed a robotic system to systematically evaluate participants' perception of locomotor-feedback in relation to potential adaptation of their gait. To this end, the FeetBack system enabled us to non-invasively remap steprelated feedback from participants' foot soles to their own back during natural over-ground walking.…”