A Human−Computer Interface Replacing Mouse and Keyboard for Individuals with Limited Upper Limb Mobility

People with physical disabilities in their upper extremities face serious issues in using classical input devices due to lacking movement possibilities and precision. This article suggests an alternative input concept and presents corresponding input devices. The proposed interface combines an inertial measurement unit and force sensing resistors, which can replace mouse and keyboard. Head motions are mapped to mouse pointer positions, while mouse button actions are triggered by contracting mastication muscles. The contact pressures of each fingertip are acquired to replace the conventional keyboard. To allow for complex text entry, the sensory concept is complemented by an ambiguous keyboard layout with ten keys. The related word prediction function provides disambiguation at word level. Haptic feedback is provided to users corresponding to their virtual keystrokes for enhanced closed-loop interactions. This alternative input system enables text input as well as the emulation of a two-button mouse

Altered Cortico-Cortical Brain Connectivity During Muscle Fatigue

Traditional brain activation studies using neuroimaging such as functional magnetic imaging (fMRI) have shown that muscle fatigue at submaximal intensity level is associated with increased brain activity in various cortical regions from low- to high-order motor centers. However, how these areas might interact remain unclear since previous activation studies related to motor control could not reveal information of between-area interaction. This issue can be addressed by evaluating brain activation data using the framework of connectivity analysis. Three types of brain connectivity, functional connectivity (FC), effective connectivity (EC) and structural connectivity (SC) have been examined to investigate the effect of voluntary muscle fatigue on the interaction within the cortical motor network. The aim of the study was to propose a new framework to reveal adaptive interactions among motor regions during progressive muscle fatigue. We hypothesized that the brain would exhibit fatigue-related alterations in the FC and EC. Ten healthy subjects performed repetitive handgrip contractions (3.5s ON/6.5s OFF) for 20 minutes at 50 maximal voluntary force (MVC) level using the right hand (fatigue task). Significant MVC reduction occurred at the end of the fatigue task, indicating muscle fatigue. Histogram and quantile analysis confirmed that FC of the brain increased in the severe fatigue stage (the last 100s of the fatigue task) compared with the minimal fatigue stage (the first 100s of the fatigue task). Structural equation modeling (SEM) was used to evaluate the EC of the brain during fatigue. We found the path from the prefrontal cortex (PFC) to the supplementary motor area (SMA) decreased during fatigue while the path from the premotor area (PMA) to the primary motor cortex (M1) increased. We also found supporting evidence from SC analysis using diffusion tensor image (DTI). The new framework of connectivity analysis, combining the work of SC, FC and EC, provides greater insights into the dynamic adaptations of int

Altered Cortico-Cortical Brain Connectivity During Muscle Fatigue

Traditional brain activation studies using neuroimaging such as functional magnetic imaging (fMRI) have shown that muscle fatigue at submaximal intensity level is associated with increased brain activity in various cortical regions from low- to high-order motor centers. However, how these areas might interact remain unclear since previous activation studies related to motor control could not reveal information of between-area interaction. This issue can be addressed by evaluating brain activation data using the framework of connectivity analysis. Three types of brain connectivity, functional connectivity (FC), effective connectivity (EC) and structural connectivity (SC) have been examined to investigate the effect of voluntary muscle fatigue on the interaction within the cortical motor network. The aim of the study was to propose a new framework to reveal adaptive interactions among motor regions during progressive muscle fatigue. We hypothesized that the brain would exhibit fatigue-related alterations in the FC and EC. Ten healthy subjects performed repetitive handgrip contractions (3.5s ON/6.5s OFF) for 20 minutes at 50 maximal voluntary force (MVC) level using the right hand (fatigue task). Significant MVC reduction occurred at the end of the fatigue task, indicating muscle fatigue. Histogram and quantile analysis confirmed that FC of the brain increased in the severe fatigue stage (the last 100s of the fatigue task) compared with the minimal fatigue stage (the first 100s of the fatigue task). Structural equation modeling (SEM) was used to evaluate the EC of the brain during fatigue. We found the path from the prefrontal cortex (PFC) to the supplementary motor area (SMA) decreased during fatigue while the path from the premotor area (PMA) to the primary motor cortex (M1) increased. We also found supporting evidence from SC analysis using diffusion tensor image (DTI). The new framework of connectivity analysis, combining the work of SC, FC and EC, provides greater insights into the dynamic adaptations of int

Applications of the electric potential sensor for healthcare and assistive technologies

The work discussed in this thesis explores the possibility of employing the Electric Potential Sensor for use in healthcare and assistive technology applications with the same and in some cases better degrees of accuracy than those of conventional technologies. The Electric Potential Sensor is a generic and versatile sensing technology capable of working in both contact and non-contact (remote) modes. New versions of the active sensor were developed for specific surface electrophysiological signal measurements. The requirements in terms of frequency range, electrode size and gain varied with the type of signal measured for each application. Real-time applications based on electrooculography, electroretinography and electromyography are discussed, as well as an application based on human movement. A three sensor electrooculography eye tracking system was developed which is of interest to eye controlled assistive technologies. The system described achieved an accuracy at least as good as conventional wet gel electrodes for both horizontal and vertical eye movements. Surface recording of the electroretinogram, used to monitor eye health and diagnose degenerative diseases of the retina, was achieved and correlated with both corneal fibre and wet gel surface electrodes. The main signal components of electromyography lie in a higher bandwidth and surface signals of the deltoid muscle were recorded over the course of rehabilitation of a subject with an injured arm. Surface electromyography signals of the bicep were also recorded and correlated with the joint dynamics of the elbow. A related non-contact application of interest to assistive technologies was also developed. Hand movement within a defined area was mapped and used to control a mouse cursor and a predictive text interface

The physiological effects of blood flow restricted muscle stimulation

Emerging evidence suggests that low load exercise stimuli can lead to significant muscular adaptations when blood flow to a muscle is restricted or occluded. Electrical muscle stimulation has been used for years in the rehabilitative settings, but muscular hypertrophic or oxidative adaptation resulting from electrical stimulation is typically of limited magnitude, likely owing to the discomfort caused by the high intensity stimulus necessary to cause greater adaptation. Combining low intensity transcutaneous electrical muscle stimulation (TEMS) with blood flow restriction (BFR) has yet to be examined, and offers the potential to stimulate substantial muscular adaptation without undue discomfort. We examined the effects of combining BFR with a low intensity TEMS on the upper and lower body musculature. Twenty recreationally active subjects (24±6 yr, 174±10 cm, 70±17kg) were recruited and had every limb randomly allocated to one of four possible training groups: 1) BFR -4mins inflated, 4 mins deflated at 220mmHg alone, 2) TEMS alone- at a maximally tolerable intensity, 3) BFR+TEMS (COMB), or 4) control (CON). Each arm and leg was “trained” in its respective intervention group four times weekly for six weeks. To test muscular adaptation, muscle size and strength were measured at baseline and following 6 weeks of stimuli. Mean differences in size (g) and strength (kg), between week 0 and week 6, were calculated for each intervention group. ARM: After 6 weeks of training, the COMB group changed by 45±201g and 3.2 ±3.6kg, whereas the BFR group changed by 21±103g and 2.6±3.9kg. The TEMS group changed by -37±121 g and 0.7±3.0kg; while the CON group changed by and 4±78g and 0.6±2.9kg. There was no significant difference between groups for maximal strength (p=0.2) or size (p=0.4). LEG: Leg strength changed by 32±19 kg in the COMB group and was significantly different than the 3±11kg change in the CON group (p=0.03). The TEMS and BFR group changed by 16±28kg and 18±17kg, respectively. There were no other significant differences between groups. Leg size changed by 95±238g in the COMB group; whereas size changed by 79±439g and 26±387g in the TEMS and BFR groups, respectively. The CON group changed by -83±279g. There were no significant differences between groups for leg size. The results suggest no effect of the intervention, however, despite a relative lack of overall statistical significance, owing to large individual variability in response, there is an indication of a possible effect. The absence of significance in most comparisons is likely explicable by the high inter-individual variability and differential adaptive responses

Sensor Developments for Electrophysiological Monitoring in Healthcare

Recent years have seen a renewal of interest in the development of sensor systems which can be used to monitor electrophysiological signals in a number of different settings. These include clinical, outside of the clinical setting with the subject ambulatory and going about their daily lives, and over long periods. The primary impetus for this is the challenge of providing healthcare for the ageing population based on home health monitoring, telehealth and telemedicine. Another stimulus is the demand for life sign monitoring of critical personnel such as fire fighters and military combatants. A related area of interest which, whilst not in the category of healthcare, utilises many of the same approaches, is that of sports physiology for both professional athletes and for recreation. Clinical diagnosis of conditions in, for example, cardiology and neurology remain based on conventional sensors, using established electrodes and well understood electrode placements. However, the demands of long term health monitoring, rehabilitation support and assistive technology for the disabled and elderly are leading research groups such as ours towards novel sensors, wearable and wireless enabled systems and flexible sensor arrays

The effects of augmentative and alternative communication cursor click modality on language complexity and user perceptions

PURPOSE: Surface electromyography (sEMG) provides an alternative method for individuals with severe motor impairments to use the voluntary contractions of sparred musculature as inputs into an alternative and augmentative communication (AAC) device. Current research suggests that individuals with typical motor control prefer a sEMG-based click mechanism over a dwell-based click mechanism to operate an on-screen cursor. However, there is no existing data on the effects of cursor click modality on language production in AAC users with motor impairments. The goal of this study was to evaluate the communicative abilities of individuals with neuromuscular disorders when using an AAC device with two different cursor click modalities. METHOD: Twelve individuals with neuromuscular disorders produced synthetic language samples via an on-screen keyboard using an sEMG/accelerometer system with two different click modalities: dwell-based clicking and sEMG-based clicking. A third language sample via natural speech was also recorded. Language sample analysis was used to evaluate language complexity at syntactic, semantic, and ideational levels. To analyze syntactic complexity, language samples were examined for clausal density, conjunction usage, phrase expansions (noun phrase, verb phrase, and prepositional phrase), and mean length of utterance. Semantic complexity was analyzed using measures of moving-average type token ratio, abstract noun usage, metacognitive verb usage, and usage of morphologically complex words. Ideational complexity was analyzed in terms of the extent to which the responses conveyed the participant’s ideas. A questionnaire was used to measure the participants’ perceptions of usefulness for each modality. RESULTS: Mean length of utterance was shorter in the dwell-based click modality than in the sEMG-based click and natural speech modalities. In the sEMG-based click modality the majority of sentences were complex sentences, whereas simple sentences made up the majority in the dwell-based click modality. Morphologically complex word usage was used more frequently in the natural speech modality than in the sEMG-based click modality and used most frequently in the dwell-based click modality. There were no modality-specific trends for ideational complexity. Measures from the questionnaire showed that participants ranked natural speech as being more useful than either of the cursor-click modalities, but all three modalities were rated as at least somewhat useful (5 out of 7 on a rating scale of usefulness). CONCLUSION: This study is the first to evaluate the effects of cursor-click modality on the communicative abilities of individuals with neuromuscular disorders. Despite differences in language complexity on some measures, participants were able to use all three modalities to accurately respond to the language prompt with similar ideational scores. These results support both sEMG and dwell as alternative access methods for controlling a cursor-click system for individuals with neuromuscular disorders in future AAC applications

The Influence of Dopamine Replacement on Movement Impairments During Bimanual Coordination in Parkinson’s Disease (PD)

The purpose of the current thesis was to investigate the influence of dopamine replacement on performance during bimanual coordination in individuals with Parkinson’s disease (PD) There has been conflicting research on the cause of movement impairments such as coordination deficits, slowed switching and upper limb freezing that occur during coordinated movements It is unclear whether decreased function of the dopaminergic system after withdrawal from dopamine replacement is responsible for these deficits Healthy age-matched control participants were compared to PD participants in two experiments to determine the movement impairments that occurred during three-dimensional wrist flexion-extension bimanual coordination as a result of PD. In addition, individuals with PD were compared without (‘off’) and with (‘on’) dopamine replacement in both experiments to determine whether modulation of the dopaminergic system influenced coordinated movements. In Experiment 1, continuous bimanual coordination was performed in m-phase (simultaneous wrist flexion and extension) and anti-phase (flexion of one wrist while extending other wrist) with movements externally paced with increasing across seven cycle frequencies (0.75 to 2 Hz). Visual feedback was also manipulated in one of three sensory conditions no vision, normal vision or augmented vision. Visual feedback, phase and cycle frequency manipulation was performed to determine whether other deficits (e.g. sensory and/or attentional deficits) may influence coordinated movements Despite reduced amplitude of movements in both limbs of individuals with PD (PD ‘off’), coordination deficits were not observed in PD compared to healthy control participants. In addition, there was an increased occurrence of upper limb freezing (ULF) when cycle frequency demand was greater Dopamine replacement did increase the amplitude of movements in individuals with PD but did not influence coordination performance or the occurrence of ULF. In Experiment 2, coordinated movements were initiated in either m-phase or antiphase and participants were required to voluntarily switch to the other phase pattern when an auditory cue was presented Trials were performed at one of two cycle frequencies (1 or 2 Hz) and one of two sensory conditions (no vision or normal vision) to determine whether other deficits (e.g. sensory and/or attentional deficits) may influence coordinated movement. In addition, a separate block of trials were performed in anti-phase coordination with an auditory cue that did not require a switch Non-switching trials were included to investigate whether the presence of a distracting cue could evoke ULF comparable to when switching between movements was required PD ‘off’ participants demonstrated slower switching, more delayed responses and deficits in coordination performance when compared to healthy control participants. The increased demand of cycle frequency particularly when initiating anti-phase coordination, after voluntary switching and with the presence of the auditory cue without switching contributed to a large occurrence of ULF in individuals with PD. Dopamine replacement improved the ability to switch between phase patterns but had no overall influence on coordination performance or the occurrence of ULF. Overall, the results of the current thesis demonstrated that dopamine replacement can improve motor symptoms during coordinated movements (e g hypometna and bradykinesia) but does not contribute to coordination performance or ULF in individuals with PD. As a consequence, it was concluded that coordination deficits and ULF are not caused by the dysfunctional dopaminergic system but rather associated to secondary impairment caused by PD. The movement impairments caused by secondary dysfunction of PD were proposed to be associated with increased attentional demands and possible executive dysfunction related to fronto-stnatal pathways that cannot be modulated by dopamine replacement. Thus, treatment of complex movement impairments such as coordination deficits and ULF may benefit from rehabilitation or non-dopamine therapies that focus on the global dysfunction caused by PD