Intracortical Somatosensory Stimulation to Elicit Fingertip Sensations in an Individual With Spinal Cord Injury

Background and Objectives:The restoration of touch to fingers and fingertips is critical to achieving dexterous neuroprosthetic control for individuals with sensorimotor dysfunction. However, localized fingertip sensations have not been evoked via intracortical microstimulation (ICMS).Methods:Using a novel intraoperative mapping approach, we implanted electrode arrays in the finger areas of left and right somatosensory cortex and delivered ICMS over a 2-year period in a human participant with spinal cord injury.Results:Stimulation evoked tactile sensations in 8 fingers, including fingertips, spanning both hands. Evoked percepts followed expected somatotopic arrangements. The subject was able to reliably identify up to 7 finger-specific sites spanning both hands in a finger discrimination task. The size of the evoked percepts was on average 33% larger than a fingerpad, as assessed via manual markings of a hand image. The size of the evoked percepts increased modestly with increased stimulation intensity, growing 21% as pulse amplitude increased from 20µA to 80µA. Detection thresholds were estimated on a subset of electrodes, with estimates of 9.2-35µA observed, roughly consistent with prior studies.Discussion:These results suggest that ICMS can enable the delivery of consistent and localized fingertip sensations during object manipulation by neuroprostheses for individuals with somatosensory deficits.Clinical Trial Information:This study is registered on ClinicalTrials.gov with identifier NCT03161067.

When Right Goes Left: Phantom Touch Induced by Mirror Box Procedure in Healthy Individuals

In the present article, we investigated the possibility of inducing phantom tactile sensations in healthy individuals similar to those that we observed in patients after stroke. On the basis of previous research, we assumed that manipulating visual feedbacks may guide and influence, under certain conditions, the phenomenal experience of touch. To this aim, we used the Tactile Quadrant Stimulation (TQS) test in which subjects, in the crucial condition, must indicate whether and where they perceive a double tactile stimulation applied simultaneously in different quadrants of the two hands (asymmetrical Double Simultaneous Stimulation trial, Asym-DSS). The task was performed with the left-hand out of sight and the right-hand reflected in a mirror so that the right-hand reflected in the mirror looks like the own left-hand. We found that in the Asym-DSS trial, the vision of the right-hand reflected in the mirror and stimulated by a tactile stimulus elicited on the left-hand the sensation of having been touched in the same quadrant as the right-hand. In other words, we found in healthy subjects the same phantom touch effect that we previously found in patients. We interpreted these results as modulation of tactile representation by bottom-up (multisensory integration of stimuli coming from the right real and the right reflected hand) and possibly top-down (body ownership distortion) processing triggered by our experimental setup, unveiling bilateral representation of touch.

Masking and Synergy of Sensory Indicators of Product Quality

The article presents an overview of methods for improving the sensory characteristics of food, beverages and dishes: masking and synergy. Masking is understood as hiding undesirable or obviously negative characteristics of products by taste, smell, appearance. To mask the undesirable taste and smell, the most widely used flavor and aroma compositions, which allow not only to block the negative characteristics, but also to give the product a new taste and smell. The use of salt, sugar and its analogues, seasonings, triglycerides with a high content of fatty acids help to hide the taste negative characteristics. In pharmaceuticals, the most common way to mask the bitter taste of a drug is to encapsulate or cover the drug with polymers that block the interaction of taste receptors and the bitter compound. Masking the appearance of food products is primarily achieved by the use of dyes. Synergy is understood as an increase in the intensity of sensation (taste, smell, appearance, texture) as a result of the joint action of several modalities. It has been shown that taste and smell have a strong synergistic effect and often determine the quality of food products. Adding small amounts of salt, sugar, and food acid to a product, dish, or drink at the level of sensation thresholds allows you to enhance both the taste and aroma perception of the product. The taste sensations can also be affected by the color of the product: red and orange products are perceived more sweet, yellow with a lemon tint gives a feeling of sourness of the product, green-freshness and brown and black-increases the feeling of bitterness. The structure of a dish or drink affects the taste and olfactory indicators, so the flavor of the product is formed from the joint sensations of taste, aroma and tactile sensations in the oral cavity. The conducted marketing research on the influence of sound on taste sensations showed: so a crunchy cucumber is perceived as more delicious than a less crunchy one, and the crunch of chips is directly associated with their quality indicators.

Miniaturization of mechanical actuators in skin-integrated electronics for haptic interfaces

Skin-integrated electronics, also known as electronic skin (e-skin), are rapidly developing and are gradually being adopted in biomedical fields as well as in our daily lives. E-skin capable of providing sensitive and high-resolution tactile sensations and haptic feedback to the human body would open a new e-skin paradigm for closed-loop human–machine interfaces. Here, we report a class of materials and mechanical designs for the miniaturization of mechanical actuators and strategies for their integration into thin, soft e-skin for haptic interfaces. The mechanical actuators exhibit small dimensions of 5 mm diameter and 1.45 mm thickness and work in an electromagnetically driven vibrotactile mode with resonance frequency overlapping the most sensitive frequency of human skin. Nine mini actuators can be integrated simultaneously in a small area of 2 cm × 2 cm to form a 3 × 3 haptic feedback array, which is small and compact enough to mount on a thumb tip. Furthermore, the thin, soft haptic interface exhibits good mechanical properties that work properly during stretching, bending, and twisting and therefore can conformally fit onto various parts of the human body to afford programmable tactile enhancement and Braille recognition with an accuracy rate over 85%.

Bilaterally Shared Haptic Perception for Human-Robot Collaboration in Grasping Operation

Tactile sensations are crucial for achieving precise operations. A haptic connection between a human operator and a robot has the potential to promote smooth human-robot collaboration (HRC). In this study, we assemble a bilaterally shared haptic system for grasping operations, such as both hands of humans using a bottle cap-opening task. A robot arm controls the grasping force according to the tactile information from the human that opens the cap with a finger-attached acceleration sensor. Then, the grasping force of the robot arm is fed back to the human using a wearable squeezing display. Three experiments are conducted: measurement of the just noticeable difference in the tactile display, a collaborative task with different bottles under two conditions, with and without tactile feedback, including psychological evaluations using a questionnaire, and a collaborative task under an explicit strategy. The results obtained showed that the tactile feedback provided the confidence that the cooperative robot was adjusting its action and improved the stability of the task with the explicit strategy. The results indicate the effectiveness of the tactile feedback and the requirement for an explicit strategy of operators, providing insight into the design of an HRC with bilaterally shared haptic perception.

Quantifying the Generation Process of Multi-Level Tactile Sensations via ERP Component Investigation

Humans obtain characteristic information such as texture and weight of external objects, relying on the brain’s integration and classification of tactile information; however, the decoding mechanism of multi-level tactile information is relatively elusive from the temporal sequence. In this paper, nonvariant frequency, along with the variant pulse width of electrotactile stimulus, was performed to generate multi-level pressure sensation. Event-related potentials (ERPs) were measured to investigate the mechanism of whole temporal tactile processing. Five ERP components, containing P100–N140–P200–N200–P300, were observed. By establishing the relationship between stimulation parameters and ERP component amplitudes, we found the following: (1) P200 is the most significant component for distinguishing multi-level tactile sensations; (2) P300 is correlated well with the subjective judgment of tactile sensation. The temporal sequence of brain topographies was implemented to clarify the spatiotemporal characteristics of the tactile process, which conformed to the serial processing model in neurophysiology and cortical network response area described by fMRI. Our results can help further clarify the mechanism of tactile sequential processing, which can be applied to improve the tactile BCI performance, sensory enhancement, and clinical diagnosis for doctors to evaluate the tactile process disorders by examining the temporal ERP components.

Virtual and Augmented Reality Changing Horizons in Dentistry

Augmented and virtual reality (AR-VR) is a fast developing technology that has been used in the field of medicine for a long time. It has also found its way in dentistry and the preliminary assessments so far have shown promising results. Aim: The presented scoping review was conducted with an aim of identifying the current applications of AR-VR in the field of dental training and education. The paper also highlights the presently available dental simulators, their features and areas of use. Result: It was found that AR-VR is not restricted to teaching of upcoming dentists but also helps practicing physicians to return to basics and refine their skills. Inclusion of haptics provides a realistic experience by simulating the tactile sensations. Instant feedback feature act as a source of motivation to cover the missed bases. Conclusion: AR-VR technology has numerous advantages in dental education and training. However, the currently available systems require imports and are bulky to be transported in difficult terrains. Thereby it is important that indigenous systems be developed that have enhanced feasibility to be used for training of Armed Forces for managing trauma cases encountered in the field.

INTERACTION OF CLOTHING IN THERMOREGULATION IN THE CASE OF PRETERM INFANTS

The paper presents a study about the thermoregulation in the case of premature babies and the importance and influence of their clothing in this complex process. The temperature of premature babies has to be between 36.5 - 37.5°C but, hypothermia (axillary temperature <36.5°C) is a common situation. This is primarily due to a large surface area and metabolic mass ratio that results in heat loss. Hypothermia among new-borns is considered an important contributor to neonatal morbidity and mortality. In this context, it has been identified that clothing products are recommended to maintain the optimal body temperature for those born prematurely. The elaborate clothing products aim at maintaining a thermal comfort and certain physiological indicators. Skin temperature and tactile sensations also play an important role in the growth and development of premature babies. In this regard, 15 premature infants were used as study subjects and their temperature profile was recorded. The proposed clothes aimed to maintain the baby's temperature in the normal range and provide a pleasant aesthetic appearance, while helping to improve the medical manipulations to which these children are subjected.

The science and engineering behind sensitized brain-controlled bionic hands

Advances in our understanding of brain function, along with the development of neural interfaces that allow for the monitoring and activation of neurons, have paved the way for brain machine interfaces (BMI), which harness neural signals to reanimate the limbs via electrical activation of the muscles, or to control extra-corporeal devices, thereby bypassing the muscles and senses altogether. BMIs consist of reading out motor intent from the neuronal responses monitored in motor regions of the brain and executing intended movements using bionic limbs, reanimated limbs, or exoskeletons. BMIs also allow for the restoration of the sense of touch by electrically activating neurons in somatosensory regions of the brain, thereby evoking vivid tactile sensations and conveying feedback about object interactions. In this review, we discuss the neural mechanisms of motor control and somatosensation in able-bodied individuals and describe approaches to use neuronal responses as control signals for movement restoration and to activate residual sensory pathways to restore touch. While the focus of the review is on intracortical approaches, we also describe alternative signal sources for control and non-invasive strategies for sensory restoration.