Background Tactile stimulation can be used to convey information to a user in different scenarios while avoiding overloading other senses. Tactile messages can be transmitted as spatial patterns, potentially allowing for a high information throughput. The aim of the present study was to design and test different encoding schemes to determine the best approach for conveying spatial patterns. Methods Encoding schemes with simultaneous (SIM) and sequential pad activation (SEQ) were evaluated, including four SEQ variants designed to potentially facilitate the recognition. In SEQ‐col and SEQ‐row, the column and row of the activated pad were signified using different frequencies, while SEQ‐all and SEQ‐all‐fast included the activation of all pads where those belonging to the pattern were indicated by changes in frequency (ON pads). The success rate (SR) of the pattern identification and the response time were quantified in 15 participants who recognized 20 patterns delivered through a 3 × 2 pad matrix placed on the lateral torso. Results SIM was not a feasible method to present the patterns (median, 15%; IQR, 5%). The SR improved with SEQ (median, 60%; IQR, 20%) and further increased with additional cues, particularly with SEQ‐row (median, 78.3%; IQR, 23.3%) and SEQ‐all (median, 96.7%; IQR, 5%). Importantly, the stimulation time of SEQ‐all could be decreased without a substantial drop in accuracy (SEQ‐all‐fast: median, 89.2%; IQR, 19.2%). Conclusions The spatiotemporal stimulation with sequential activation of all pads (SEQ‐all) seems to be the method of choice when conveying tactile messages as spatial patterns. This is an important outcome for increasing the information bandwidth of communication through the tactile channel.

No abstract

Electrotactile stimulation is a technology that reproducibly elicits tactile sensations and can be used as an alternative channel to communicate information to the user. The presented work is a part of an effort to develop this technology into an unobtrusive communication tool for first responders. In this study, the aim was to compare the success rate (SR) between discriminating stimulation at six spatial locations (static encoding) and recognizing six spatio-temporal patterns where pads are activated sequentially in a predetermined order (dynamic encoding). Additionally, a procedure for a fast amplitude calibration, that includes a semi-automated initialization and an optional manual adjustment, was employed and evaluated. Twenty subjects, including twelve first responders, participated in the study. The electrode comprising the 3 × 2 matrix of pads was placed on the lateral torso. The results showed that high SRs could be achieved for both types of message encoding after a short learning phase; however, the dynamic approach led to a statistically significant improvement in messages recognition (SR of 93.3%), compared to static stimulation (SR of 83.3%). The proposed calibration procedure was also effective since in 83.8% of the cases the subjects did not need to adjust the stimulation amplitude manually.

No abstract

Phasic pain stimuli are inhibited when they are applied concomitantly with a conditioning tonic stimulus at another body location (Heterotopic Noxious Conditioning Stimulation, HNCS). While this effect is thought to rely on a spino-bulbospinal mechanism in animals (Diffuse Noxious Inhibitory Controls, DNIC), the underlying neurophysiology in humans may further involve other pathways. In this study, we investigated the role of supraspinal mechanisms in HNCS by presenting auditory stimuli during a conditioning tonic painful stimulus (the Cold Pressor Test, CPT). Considering that auditory stimuli are not conveyed through the spinal cord, any changes in brain responses to auditory stimuli during HNCS can be ascribed entirely to supraspinal mechanisms. High-density electroencephalography (EEG) was recorded during HNCS and auditory stimuli were administered in three blocks, before, during, and after HNCS. Nociceptive Withdrawal Reflexes (NWRs) were recorded at the same time points to investigate spinal processing. Our results showed that AEPs were significantly reduced during HNCS. Moreover, the amplitude of the NWR was significantly diminished during HNCS in most participants. Given that spinal and supraspinal mechanisms operate concomitantly during HNCS, the possibility of isolating their individual contributions to DNIC-like effects in humans is questionable. We conclude that the net effects of HCNS cannot be measured independently from attentional/cognitive influences.