Creating tactile feedback with intelligent electrical stimulation to compensate for sensory impairment.

Performing daily life activities can be more challenging as a result of peripheral neuropathy in the feet and can lead to an increased risk of falls and injuries. Biofeedback, in the form of electrocutaneous stimulation, can be used as a means to transmit information about the force and pressure applied to the feet, and this can help people determine their body position in relation to the ground and the amount of sway movements. The motivation for the present work was to explore whether a wearable electrotactile feedback system (EFS) could improve life quality by supporting people with balance instability as a result of this condition. In this study a wearable EFS was designed to estimate the magnitude of pressure applied to the feet during standing and walking. The study also aimed to determine whether the EFS had an effect on posture control in standing and confidence in walking among individuals suffering from peripheral neuropathy. A wearable EFS has been developed in this work including the hardware design for an electrocutaneous stimulation and a processing unit to compute the sensor data. The EFS uses a sensor system with piezoresitive force sensors that has been developed and tested beforehand. The proposed system considers aspects of safety and portability, as well as meeting individual parameters. The latter one was assured by implementing and testing a novel calibration method for the detection of sensory thresholds and device parameters. A software for magnitude estimation and force and pressure feedback based on the centre of pressure (COP) movement was programmed and a psychophysical transfer function involving sensory thresholds and sensor system variables was implemented. A pilot study with 11 participants was carried out to evaluate the suitability of the EFS for magnitude estimation. Magnitude estimation with the EFS showed high accuracy and sensitivity and it was found that the design proposed in this work is beneficial over other solutions. The upper leg was identified as a suitable location for electrotactile feedback. A proof of concept study was undertaken among 14 individuals suffering with peripheral neuropathy and five controls in a clinical environment, testing the effects of the EFS on balancing and walking in different scenarios. It was shown that, when used by patients with neuropathy, the EFS helped improving posture control in certain scenarios and did not hinder patients during walking. A longer learning period might be necessary so that users can fully benefit from the EFS. The findings of the study contribute to the understanding of electrotactile feedback and are valuable for further developments of wearable EFS to compensate for sensory impairment and improve activities of daily life for people with sensation loss in their feet

A fabric-based approach for wearable haptics

In recent years, wearable haptic systems (WHS) have gained increasing attention as a novel and exciting paradigm for human-robot interaction (HRI).These systems can be worn by users, carried around, and integrated in their everyday lives, thus enabling a more natural manner to deliver tactile cues.At the same time, the design of these types of devices presents new issues: the challenge is the correct identification of design guidelines, with the two-fold goal of minimizing system encumbrance and increasing the effectiveness and naturalness of stimulus delivery.Fabrics can represent a viable solution to tackle these issues.They are specifically thought “to be worn”, and could be the key ingredient to develop wearable haptic interfaces conceived for a more natural HRI.In this paper, the author will review some examples of fabric-based WHS that can be applied to different body locations, and elicit different haptic perceptions for different application fields.Perspective and future developments of this approach will be discussed

The neural basis of perceived intensity in natural and artificial touch

Electrical stimulation of sensory nerves is a powerful tool for studying neural coding because it can activate neural populations in ways that natural stimulation cannot. Electrical stimulation of the nerve has also been used to restore sensation to patients who have suffered the loss of a limb. We have used long-term implanted electrical interfaces to elucidate the neural basis of perceived intensity in the sense of touch. To this end, we assessed the sensory correlates of neural firing rate and neuronal population recruitment independently by varying two parameters of nerve stimulation: pulse frequency and pulse width. Specifically, two amputees, chronically implanted with peripheral nerve electrodes, performed each of three psychophysical tasks-intensity discrimination, magnitude scaling, and intensity matching-in response to electrical stimulation of their somatosensory nerves. We found that stimulation pulse width and pulse frequency had systematic, cooperative effects on perceived tactile intensity and that the artificial tactile sensations could be reliably matched to skin indentations on the intact limb. We identified a quantity we termed the activation charge rate (ACR), derived from stimulation parameters, that predicted the magnitude of artificial tactile percepts across all testing conditions. On the basis of principles of nerve fiber recruitment, the ACR represents the total population spike count in the activated neural population. Our findings support the hypothesis that population spike count drives the magnitude of tactile percepts and indicate that sensory magnitude can be manipulated systematically by varying a single stimulation quantity

Encoding tactile frequency and intensity information in the temporal pattern of afferent nerve impulses

Using our hands to interact with the world around us produces complex vibrations travelling across the skin. These complex waves are transduced by tactile afferent neurons whose impulse patterns convey information about the external world. A major question in this field is how important the timing of these afferent impulses is in shaping perception. We have the means to investigate this question by artificially inducing impulse patterns using brief mechanical and electrical stimuli, allowing us to study the neural coding of vibrotactile sensory information. Our lab has used this to show that when mechanical pulses evoked impulse trains grouped into periodic bursts, perceived frequency corresponded to the duration of the silent inter-burst gap interval, rather than the periodicity or the mean impulse rate. In this thesis, we induced controlled impulse trains, while measuring the perceptual responses of human subjects using psychophysical methods to assess the dimensions of frequency and intensity. As electrical stimulation has broad utility in prosthetic applications, we first verified that the same perceived frequency as predicted by the burst gap was elicited with electrical pulses in subjects within the low frequency flutter range. We then tested whether this same coding mechanism also applied outside the flutter frequency range by conducting further experiments with higher pulse rates. We found that burst gap coding correctly predicted perceived frequencies above flutter, suggesting a generalised temporal processing strategy that operates on tactile afferent inputs spanning a broad range of frequencies. Next, we investigated perceived intensity where stimulus pulse rate was varied without changes in afferent population recruitment or in perceived frequency by using bursts of pulsatile stimuli. Increasing the number of pulses within a burst caused a significant increase in perceived intensity when electrical stimulation was used. Mechanical pulses with the same burst groupings did not produce a comparable intensity increase, possibly due to minimal variations in the population firing rate. These new insights into the encoding of tactile information through temporal patterning in peripheral impulse patterns may allow the multiplexing of frequency and intensity sensations with a fixed stimulation amplitude for use in neural interfaces to deliver sensory feedback information

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Design of a vibrotactile stimulus paradigm for a biofeedback device to improve gait rehabilitation of lower limb amputees

Dissertação de mestrado integrado em Biomedical Engineering (specialization in Biomaterials Rehabilitation and Biomechanics)A lower limb amputation not only affects locomotion, but also the amputee's somatosensory system, body perception, and mental health and, naturally, the fear of falling is more pronounced. Consequently, the patient is faced with the challenge of developing motor strategies that allow him to carry out daily activities since the use of the prosthesis does not fully compensate for the deficiencies acquired by a prosthetic gait, such as, for instance, asymmetry and variation in the duration of the gait events. Faced with the absence of effective treatments that restore locomotor functionality, the BioWalk project presents a rehabilitation solution: a biofeedback system that assists amputees during gait training sessions. This system consists in applying a vibrotactile stimulus on the skin of the affected leg. This stimulus can be activated at different moments of the prosthetic gait, allowing the patient to have a better perception and awareness of his body and locomotion to be able to detect any abnormal motor behaviours during the rehabilitation sessions and, in the future, to establish an adequate and healthy gait pattern. Consequently, there is a need to analyse muscular and kinematic data of the gait of amputees to detect which events are critical in prosthetic gait, which muscles are activated or most required in gait, how the centre of mass behaves in the gait of an amputee, among other parameters. Thus, in this dissertation, the main goal is to investigate and propose the best way (i.e., paradigm) to apply a vibrotactile stimulus to be used in a biofeedback device during rehabilitation sessions.Uma amputação do membro inferior não afeta apenas a locomoção, mas também o sistema somatosensorial do amputado, a sua perceção corporal, a sua saúde mental e, naturalmente, o medo de cair encontra-se mais acentuado. Consequentemente, o paciente é confrontado com o desafio de desenvolver estratégias motoras que lhe permitam a realização de atividades diárias dado que o uso da prótese não compensa totalmente as deficiências adquiridas por uma marcha protética, como por exemplo, a assimetria e a variação na duração dos eventos de marcha. Perante a ausência de tratamentos eficazes que restaurem a funcionalidade locomotora, o projeto BioWalk apresenta uma solução de reabilitação: um sistema de biofeedback que auxilie a pessoa amputada durante sessões de treino de marcha. Este sistema consiste na aplicação de um estímulo vibrotátil sobre a pele da perna afetada. Este estímulo pode ser ativado em diversos momentos da marcha protética permitindo ao paciente uma melhor percetibilidade e consciência sobre o seu corpo e locomoção para que seja capaz de detetar algum comportamento motor anormal durante as sessões de reabilitação e para, futuramente, estabelecer um padrão de marcha adequado e saudável. Consequentemente, surge a necessidade de analisar dados musculares e cinemáticos da marcha de amputados de forma a detetar quais os eventos críticos na marcha protética, quais são os músculos ativados ou os que são mais requeridos na marcha, como se comporta o centro de massa na marcha de um amputado, entre outros parâmetros. Assim, nesta dissertação, o objetivo é propor um paradigma de estímulos vibrotáteis para serem usados num dispositivo de biofeedback durante sessões de reabilitação

Engineering Data Compendium. Human Perception and Performance, Volume 1

The concept underlying the Engineering Data Compendium was the product an R and D program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design of military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by system designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is Volume 1, which contains sections on Visual Acquisition of Information, Auditory Acquisition of Information, and Acquisition of Information by Other Senses

A forearm controller and tactile display

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Includes bibliographical references (leaves 187-192).This thesis discusses the design and implementation of ARMadillo, a simple virtual environment interface in the form of a small wireless device that is worn on the forearm. Designed to be portable, intuitive, and low cost, the device tracks the orientation of the arm with accelerometers, magnetic field sensors, and gyroscopes, fusing the data with a quaternion based Unscented Kalman Filter. The orientation estimate is mapped to a virtual space that is perceived through a tactile display containing an array of vibrating motors. The controller is driven with an 8051 microcontroller, and includes a BlueTooth module and an extension slot for CompactFlash cards. The device was designed to be simple and modular, and can support a variety of interesting applications, some of which were implemented and will be discussed. These fall into two main classes. The first is a set of artistic applications, represented by a suite of virtual musical instruments that can be played with arm movements and felt through the tactile display, The second class involves utilitarian applications, including a custom Braille-like system called Arm Braille, and tactile guidance. A wearable Braille display intended to be used for reading navigational signs and text messages was tested on two sight-impaired subjects who were able to recognize Braille characters reliably after 25 minutes of training, and read words by the end of an hour.by David Matthew Sachs.S.M