Skin-Attached Arrayed Piezoelectric Sensors for Continuous and Safe Monitoring of Oculomotor Movements.

Abnormal oculomotor movements are known to be linked to various types of brain disorders, physical/mental shocks to the brain, and other neurological disorders, hence its monitoring can be developed into a simple but effective diagnostic tool. To overcome the limitations in the current eye-tracking system and electrooculography, a piezoelectric arrayed sensor system is developed using single-crystalline III-N thin-film transducers, which offers advantages of mechanical flexibility, biocompatibility, and high electromechanical conversion, for continuous monitoring of oculomotor movements by skin-attachable, safe, and highly sensitive sensors. The flexible piezoelectric eye movement sensor array (F-PEMSA), consisting of three transducers, is attached to the face temple area where it can be comfortably wearable and can detect the muscles' activity associated with the eye motions. Output voltages from upper, mid, and lower sensors (transducers) on different temple areas generate discernable patterns of output voltage signals with different combinations of positive/negative signs and their relative magnitudes for the various movements of eyeballs including 8 directional (lateral, vertical, and diagonal) and two rotational movements, which enable various types of saccade and pursuit tests. The F-PEMSA can be used in clinical studies on the brain-eye relationship to evaluate the functional integrity of multiple brain systems and cognitive processes.

A Calibration-Free Hybrid Approach Combining SSVEP and EOG for Continuous Control.

While SSVEP-BCI has been widely developed to control external devices, most of them rely on the discrete control strategy. The continuous SSVEP-BCI enables users to continuously deliver commands and receive real-time feedback from the devices, but it suffers from the transition state problem, a period the erroneous recognition, when users shift their gazes between targets. To resolve this issue, we proposed a novel calibration-free Bayesian approach by hybridizing SSVEP and electrooculography (EOG). First, canonical correlation analysis (CCA) was applied to detect the evoked SSVEPs, and saccade during the gaze shift was detected by EOG data using an adaptive threshold method. Then, the new target after the gaze shift was recognized based on a Bayesian optimization approach, which combined the detection of SSVEP and saccade together and calculated the optimized probability distribution of the targets. Eighteen healthy subjects participated in the offline and online experiments. The offline experiments showed that the proposed hybrid BCI had significantly higher overall continuous accuracy and shorter gaze-shifting time compared to FBCCA, CCA, MEC, and PSDA. In online experiments, the proposed hybrid BCI significantly outperformed CCA-based SSVEP-BCI in terms of continuous accuracy (77.61 ± 1.36%vs. 68.86 ± 1.08% and gaze-shifting time (0.93 ± 0.06s vs. 1.94 ± 0.08s). Additionally, participants also perceived a significant improvement over the CCA-based SSVEP-BCI when the newly proposed decoding approach was used. These results validated the efficacy of the proposed hybrid Bayesian approach for the BCI continuous control without any calibration. This study provides an effective framework for combining SSVEP and EOG, and promotes the potential applications of plug-and-play BCIs in continuous control.

Diagnosis of attention-deficit hyperactivity disorder using EOG signals: a new approach.

A system based on objective data was developed in the diagnosis and follow-up of attention-deficit hyperactivity disorder (ADHD) in this study. First of all, an electronic circuit, with a two-channel instrumentation amplifier designed to detect eye movements in the horizontal and vertical directions via surface electrodes, was developed to obtain the electrooculogram (EOG) signals. In order to provide a controlled analysis of eye movements during the reception of the signal, an attention test with visual stimulus software was developed. Eight patients with ADHD and eight healthy subjects were asked to monitor the stimulus images on the screen in the reference directions of the test system while recording EOG signals. According to the results of the t-test, no significant difference was found (p=0.11) between the healthy group and the reference movement information, whereas a significant difference was found between patients and the reference motion information (p=0.049). According to these results, it was seen that the number of eye movements of healthy individuals was statistically significant. In addition, they were inconsistent with the reference movement information. The level of significance was found to be low in patients. In this study, a new method is presented to test and diagnose individuals who were attention deficit.

An Affordable Method for Evaluation of Ataxic Disorders Based on Electrooculography.

Ataxias are a group of neurodegenerative disorders characterized by cerebellar dysfunction that cause irregularities in the rate, rhythm, amplitude, and force of voluntary movements. The electrooculogram (EOG) may provide clues about ataxic disorders because most of these patients have difficulty with visual tracking and fixing their gaze. Using electrodes, EOG records the biopotentials generated by eye movements. In this paper, three surface electrodes are placed around the eye socket, and the biopotentials generated by eye movements are acquired using a commercial bioamplifier device. Next, the signals are sent to the computer to be digitally processed to extract the rate of saccades as well as the delay and deviation of the gaze in response to a stimulus. These features are analysed in a novel software application designed to help physicians in evaluating ataxia. After applying several tests to both healthy and ataxia-affected patients, differences in EOG results were found. The evaluation of the reliability of the designed software application is made according to three metrics: sensitivity, specificity, and accuracy. The results indicate the proposed system's viability as an affordable method for evaluation of ataxic disorders.

The electrooculogram.

The electrooculogram (EOG) measures the cornea-positive standing potential relative to the back of the eye. By attaching skin electrodes outside the eye near the lateral and medial canthus, the potential can be measured by having the patient move the eyes horizontally a set distance. The voltage becomes smaller in the dark, reaching its lowest potential after 8-12min, the so-called dark trough. When the lights are turned on, the potential rises, reaching a peak by about 10min. When the size of the light peak is compared to the dark trough, the normal ratio should be near 2:1. A light peak:dark trough ratio of less than 1.7 is considered abnormal. The origin of electrooculographic potentials is the pigment epithelium of the retina interacting with the midretina. The light rise of the potential requires both a normal pigment epithelium and normal midretinal function. The most common use of the electrooculogram is to confirm Best disease. Best disease is identified by the appearance of an egg-yellow fundus and can be confirmed by recording both an electroretinogram (ERG) and electrooculogram (EOG). The ERG will be normal and the EOG will be abnormal. The EOG is also used for tracking eye movement.

An EOG-based wheelchair robotic arm system for assisting patients with severe spinal cord injuries.

OBJECTIVE: In this study, we combine a wheelchair and an intelligent robotic arm based on an electrooculogram (EOG) signal to help patients with spinal cord injuries (SCIs) accomplish a self-drinking task. The main challenge is to accurately control the wheelchair to ensure that the randomly located object is within a limited reachable space of the robotic arm (length: 0.8 m; width: 0.4 m; height: 0.6 m), which requires decimeter-level precision, and is still undemonstrated for EOG-based systems as well as EEG-based systems. APPROACH: A novel high-precision EOG-based human machine interface (HMI) is proposed which can effectively translate two kinds of eye movements (i.e. blinking and eyebrow raising) into various commands. For the wheelchair, positional precision can reach decimeter-level and the minimal steering angle is [Formula: see text]. For the intelligent robotic arm, shared control is implemented based on an EOG-based HMI, two cameras and the arm's own intelligence. MAIN RESULTS: After brief training, five healthy subjects and five paralyzed patients with severe SCIs successfully completed three experiments. For the healthy subjects/patients with SCIs, the system achieved an average accuracy of 99.3%/97.3%, an average response time of 1.91 s/2.02 s per command and an average stop-response time of 1.30 s/1.36 s with a 0 false operation rate. SIGNIFICANCE: The EOG-based HMI can provide sufficient precision control to integrate a wheelchair and a robotic arm into a system which can help patients with SCIs to accomplish a self-drinking task. (ChiCTR1800019764).

An EOG-Based Human-Machine Interface to Control a Smart Home Environment for Patients With Severe Spinal Cord Injuries.

OBJECTIVE: This paper presents an asyn-chronous electrooculography (EOG)-based human-machine interface (HMI) for smart home environmental control with the purpose of providing daily assistance for severe spinal cord injury (SCI) patients. METHODS: The proposed HMI allows users to interact with a smart home environment through eye blinking. Specifically, several buttons, each corresponding to a control command, randomly flash on a graphical user interface. Each flash of the buttons functions as a visual cue for the user to blink. To issue a control command, the user can blink synchronously with the flashes of the corresponding button. Through detecting blinks based on the recorded EOG signal, the target button and its corresponding control command are determined. Seven SCI patients participated in an online experiment, during which the patients were required to control a smart home environment including household electrical appliances, an intelligent wheelchair, as well as a nursing bed via the proposed HMI. RESULTS: The average false operation ratio in the control state was 4.1%, whereas during the idle state, no false operations occurred. CONCLUSION: All SCI patients were able to control the smart home environment using the proposed EOG-based HMI with satisfactory performance in terms of the false operation ratio in both the control and the idle states. SIGNIFICANCE: The proposed HMI offers a simple and effective approach for patients with severe SCIs to control a smart home environment. Therefore, it is promising to assist severe SCI patients in their daily lives.

ONEIROS, a new miniature standalone device for recording sleep electrophysiology, physiology, temperatures and behavior in the lab and field.

BACKGROUND: Sleep is an inactive state of reduced environmental awareness shared by all animals. When compared to wakefulness, sleep behavior is associated with changes in physiology and brain activity. The nature of these changes varies considerably across species, and therefore is a rich resource for gaining insight into the evolution and functions of sleep. A major obstacle to capitalizing on this resource is the lack of a small device capable of recording multiple biological parameters for extended periods of time both in the laboratory and the field. NEW METHOD: ONEIROS is a new tool designed for conducting sleep research on small, freely moving animals. The miniature, standalone system is capable of recording up to 26 electrophysiological signals (electroencephalogram, electromyogram, electrooculogram, electrocardiogram), metabolic (3 temperature channels) and behavior via an accelerometer for several days. In addition, the device is equipped with a vibrating motor which can be used to assess arousal thresholds and to disrupt sleep. The system is available in telemetric or data-logger configuration useable in the field. RESULTS: To demonstrate the efficacy of this tool, we simultaneously recorded for the first time, electroencephalogram, hippocampal local field potential, electromyogram, electrooculogram, brain, body and ambient temperature, and 3D accelerometry. We also deprived rats of paradoxical sleep by triggering the vibrating motor after online recognition of the state. Finally, by successfully recording a pigeon in an 8 m3 aviary in a social context with the device in the logger configuration, we demonstrate the feasibility of using the device in the field.

Home monitoring of sleep with a temporary-tattoo EEG, EOG and EMG electrode array: a feasibility study.

OBJECTIVE: Circadian and sleep dysfunction have long been symptomatic hallmarks of a variety of devastating neurodegenerative conditions. The gold standard for sleep monitoring is overnight sleep in a polysomnography (PSG) laboratory. However, this method has several limitations such as availability, cost and being labour-intensive. In recent years there has been a heightened interest in home-based sleep monitoring via wearable sensors. Our objective was to demonstrate the use of printed electrode technology as a novel platform for sleep monitoring. APPROACH: Printed electrode arrays offer exciting opportunities in the realm of wearable electrophysiology. In particular, soft electrodes can conform neatly to the wearer's skin, allowing user convenience and stable recordings. As such, soft skin-adhesive non-gel-based electrodes offer a unique opportunity to combine electroencephalography (EEG), electromyography (EMG), electrooculography (EOG) and facial EMG capabilities to capture neural and motor functions in comfortable non-laboratory settings. In this investigation temporary-tattoo dry electrode system for sleep staging analysis was designed, implemented and tested. MAIN RESULTS: EMG, EOG and EEG were successfully recorded using a wireless system. Stable recordings were achieved both at a hospital environment and a home setting. Sleep monitoring during a 6 h session shows clear differentiation of sleep stages. SIGNIFICANCE: The new system has great potential in monitoring sleep disorders in the home environment. Specifically, it may allow the identification of disorders associated with neurological disorders such as rapid eye movement (REM) sleep behavior disorder.

A novel EOG-based wireless rapid communication device for people with motor neuron diseases.

In this study, a new electrooculography (EOG) based system that provides efficient communication for people suffered from motor neuron diseases is presented. The system consists of two distinct devices. The first device operates as a main unit that is activated by the subject's eye movements. This unit is capable of transmitting 10 different command/state messages. These messages enable subject to choose his/her situation such as "I'm fine", "I feel bad", "I'm hungry" and "I'm thirsty". Commands such as "Come", "Go". The number of messages can be increased. The main unit acquires the EOG signal from the subject. Newly developed analogue and digital signal conditioning interprets the eye movements as specific messages and transmits them to the second unit (receiver) using radio frequency transmitter. The messages related to the subject's demands and situation can be heard from both main and receiver unit speakers. The wireless receiver unit is capable of notifying the patient's command by auditory and visual indicators. The realised device was tested by 2 healthy and 2 ALS patients and confirmed to be successful with 100% performance for sending correct messages.

Development of an electrooculogram-based eye-computer interface for communication of individuals with amyotrophic lateral sclerosis.

BACKGROUND: Electrooculogram (EOG) can be used to continuously track eye movements and can thus be considered as an alternative to conventional camera-based eye trackers. Although many EOG-based eye tracking systems have been studied with the ultimate goal of providing a new way of communication for individuals with amyotrophic lateral sclerosis (ALS), most of them were tested with healthy people only. In this paper, we investigated the feasibility of EOG-based eye-writing as a new mode of communication for individuals with ALS. METHODS: We developed an EOG-based eye-writing system and tested this system with 18 healthy participants and three participants with ALS. We also applied a new method for removing crosstalk between horizontal and vertical EOG components. All study participants were asked to eye-write specially designed patterns of 10 Arabic numbers three times after a short practice session. RESULTS: Our system achieved a mean recognition rates of 95.93% for healthy participants and showed recognition rates of 95.00%, 66.67%, and 93.33% for the three participants with ALS. The low recognition rates in one of the participants with ALS was mainly due to miswritten letters, the number of which decreased as the experiment proceeded. CONCLUSION: Our proposed eye-writing system is a feasible human-computer interface (HCI) tool for enabling practical communication of individuals with ALS.

iTrack: instrumented mobile electrooculography (EOG) eye-tracking in older adults and Parkinson's disease.

Detection of saccades (fast eye-movements) within raw mobile electrooculography (EOG) data involves complex algorithms which typically process data acquired during seated static tasks only. Processing of data during dynamic tasks such as walking is relatively rare and complex, particularly in older adults or people with Parkinson's disease (PD). Development of algorithms that can be easily implemented to detect saccades is required. This study aimed to develop an algorithm for the detection and measurement of saccades in EOG data during static (sitting) and dynamic (walking) tasks, in older adults and PD. Eye-tracking via mobile EOG and infra-red (IR) eye-tracker (with video) was performed with a group of older adults (n = 10) and PD participants (n = 10) (⩾50 years). Horizontal saccades made between targets set 5°, 10° and 15° apart were first measured while seated. Horizontal saccades were then measured while a participant walked and executed a 40° turn left and right. The EOG algorithm was evaluated by comparing the number of correct saccade detections and agreement (ICC2,1) between output from visual inspection of eye-tracker videos and IR eye-tracker. The EOG algorithm detected 75-92% of saccades compared to video inspection and IR output during static testing, with fair to excellent agreement (ICC2,1 0.49-0.93). However, during walking EOG saccade detection reduced to 42-88% compared to video inspection or IR output, with poor to excellent (ICC2,1 0.13-0.88) agreement between methodologies. The algorithm was robust during seated testing but less so during walking, which was likely due to increased measurement and analysis error with a dynamic task. Future studies may consider a combination of EOG and IR for comprehensive measurement.

Assessment of the suitability of using a forehead EEG electrode set and chin EMG electrodes for sleep staging in polysomnography.

Recently, a number of portable devices designed for full polysomnography at home have appeared. However, current scalp electrodes used for electroencephalograms are not practical for patient self-application. The aim of this study was to evaluate the suitability of recently introduced forehead electroencephalogram electrode set and supplementary chin electromyogram electrodes for sleep staging. From 31 subjects (10 male, 21 female; age 31.3 ± 11.8 years), sleep was recorded simultaneously with a forehead electroencephalogram electrode set and with a standard polysomnography setup consisting of six recommended electroencephalogram channels, two electrooculogram channels and chin electromyogram. Thereafter, two experienced specialists scored each recording twice, based on either standard polysomnography or forehead recordings. Sleep variables recorded with the forehead electroencephalogram electrode set and separate chin electromyogram electrodes were highly consistent with those obtained with the standard polysomnography. There were no statistically significant differences in total sleep time, sleep efficiency or sleep latencies. However, compared with the standard polysomnography, there was a significant increase in the amount of stage N1 and N2, and a significant reduction in stage N3 and rapid eye movement sleep. Overall, epoch-by-epoch agreement between the methods was 79.5%. Inter-scorer agreement for the forehead electroencephalogram was only slightly lower than that for standard polysomnography (76.1% versus 83.2%). Forehead electroencephalogram electrode set as supplemented with chin electromyogram electrodes may serve as a reliable and simple solution for recording total sleep time, and may be adequate for measuring sleep architecture. Because this electrode concept is well suited for patient's self-application, it may offer a significant advancement in home polysomnography.

A Motion Interference-Insensitive Flexible Dry Electrode.

OBJECTIVE: A novel dry electrode is developed to improve the comfortability and the capability of alleviating motion interference by combining microneedles array (MNA) with flexible substrate. METHODS: Silicon MNA with sharp tips and limited height is fabricated and transferred on a flexible Polydimethylsiloxane (PDMS) substrate through bonding. Poly (3, 4-ethylenedioxythiophene) doped with poly (styrenesulfonate) (PEDOT/PSS) is coated on the surface of flexible MNA to form a conductive layer. RESULTS: Flexible dry electrode with 1.2 cm diameter is successfully fabricated. The mean impedance magnitudes (measured on skin) at 10 Hz are 61.2 ±31.3 kΩ·cm(2) for flexible dry electrode, while the values are 114.9 ±36.1 kΩ·cm(2) for wet electrode and 335.7 ±110.5 kΩ·cm(2) for flexible planar dry electrode, respectively. In the process of biopotential recording, the flexible dry electrode has the similar performance as that of wet electrode. It exhibits more stable recording stability than rigid dry electrode in the movement state. CONCLUSION: By integrating flexible PDMS substrate, sharp and hard MNA structure, as well as PEDOT/PSS coated surface together, a novel dry electrode is developed to meet the comfortable and antimotion interference requirement of wearable equipment. SIGNIFICANCE: The novel flexible dry electrode provides a simple and comfortable method to record biopotential signals in daily life.

The utility of automated measures of ocular metrics for detecting driver drowsiness during extended wakefulness.

Slowed eyelid closure coupled with increased duration and frequency of closure is associated with drowsiness. This study assessed the utility of two devices for automated measurement of slow eyelid closure in a standard poor performance condition (alcohol) and following 12-h sleep deprivation. Twenty-two healthy participants (mean age=20.8 (SD 1.9) years) with no history of sleep disorders participated in the study. Participants underwent one baseline and one counterbalanced session each over two weeks; one 24-hour period of sleep deprivation, and one daytime session during which alcohol was consumed after a normal night of sleep. Participants completed a test battery consisting of a 30-min simulated driving task, a 10-min Psychomotor Vigilance Task (PVT) and the Karolinska Sleepiness Scale (KSS) each in two baseline sessions, and in two randomised, counterbalanced experimental sessions; following sleep deprivation and following alcohol consumption. Eyelid closure was measured during both tasks using two automated devices (Copilot and Optalert™). There was an increase in the proportion of time with eyelids closed and the Johns Drowsiness Score (incorporating relative velocity of eyelid movements) following sleep deprivation using Optalert (p<0.05 for both). These measures correlated significantly with crashes, PVT lapses and subjective sleepiness (r-values 0.46-0.69, p<0.05). No difference between the two sessions for PERCLOS recorded during the PVT or the driving task as measured by the Copilot. The duration of eyelid closure predicted frequent lapses following sleep deprivation (which were equivalent to the average lapses at a blood alcohol concentration of 0.05% - area under curve for ROC curve 0.87, p<0.01). The duration of time with slow eyelid closure, assessed by the automated devices, increased following sleep deprivation and was associated with deterioration in psychomotor performance and subjective sleepiness. Comprehensive algorithms inclusive of ocular parameters may be a better indicator of performance impairment following sleep loss.

Monocular Versus Binocular Calibrations in Evaluating Fixation Disparity With a Video-Based Eye-Tracker.

When measuring fixation disparity (an oculomotor vergence error), the question arises as to whether a monocular or binocular calibration is more precise and physiologically more appropriate. In monocular calibrations, a single eye fixates on a calibration target that is taken as having been projected onto the center of the fovea; the corresponding vergence state represents the heterophoria (the resting vergence position), which has no effect on the calibration procedure. In binocular calibrations, a vergence error may be present and may affect the subsequent measurement of the fixation disparity during binocular recordings. This study includes a test of the precision of both monocular and binocular calibrations and an evaluation of the impact of the calibration procedure on the measurement of fixation disparity during a dot scanning task. Our results show that 11 participants (out of 19) each exhibited a significant difference in fixation disparity with the two types of calibration procedures. In addition, the fixation disparity was more strongly affected by heterophoria undergoing monocular calibration, as opposed to binocular calibration. This serves as additional evidence showing that the monocular calibration produces a physiologically more plausible fixation disparity and seems to be more appropriate for studying the full extent of fixation disparity.

The designs and applications of a scanning interface with electrical signal detection on the scalp for the severely disabled.

This study discussed a computer-aided program development that meets the requirements of people with physical disabilities. A number of control modes, such as electrode signal recorded on the scalp and blink control, were combined with the scanning human-machine interface to improve the external input/output device. Moreover, a novel and precise algorithm, which filters noise and reduces misrecognition of the system, was proposed. A convenient assistive device can assist people with physical disabilities to meet their requirements for independent living and communication with the outside. The traditional scanning keyboard is changed, and only the phonetic notations are typed instead of characters, thus the time of tone and function selection could be saved, and the typing time could be also reduced. Barrier-free computer assistive devices and interface for people with physical disabilities in typing or speech could allow them to use a scanning keyboard to select phonetic symbols instead of Chinese characters to express their thoughts. The human-machine interface controls can obtain more reliable results as 99.8% connection success rate and 95% typing success rate.

Development of safety concept of electric wheelchair driving support system based on assessment of risk.

In this research, we pay attention to the electric wheelchair driving support. We look at the functional safety of the electric wheelchair. Based on intrinsically-safe electric wheelchair, we add driving support system to increase functional safety. The driving support system processes the environmental information sensor data including the 3D laser Range scanner and biological monitoring sensor data including electrooculogram, and assists avoidance of dangerous objects. We have developed safety concept that based on assessment of risk.

Real-time driver drowsiness feedback improves driver alertness and self-reported driving performance.

Driver drowsiness has been implicated as a major causal factor in road accidents. Tools that allow remote monitoring and management of driver fatigue are used in the mining and road transport industries. Increasing drivers' own awareness of their drowsiness levels using such tools may also reduce risk of accidents. The study examined the effects of real-time blink-velocity-derived drowsiness feedback on driver performance and levels of alertness in a military setting. A sample of 15 Army Reserve personnel (1 female) aged 21-59 (M=41.3, SD=11.1) volunteered to being monitored by an infra-red oculography-based Optalert Alertness Monitoring System (OAMS) while they performed their regular driving tasks, including on-duty tasks and commuting to and from duty, for a continuous period of 4-8 weeks. For approximately half that period, blink-velocity-derived Johns Drowsiness Scale (JDS) scores were fed back to the driver in a counterbalanced repeated-measures design, resulting in a total of 419 driving periods under "feedback" and 385 periods under "no-feedback" condition. Overall, the provision of real-time feedback resulted in reduced drowsiness (lower JDS scores) and improved alertness and driving performance ratings. The effect was small and varied across the 24-h circadian cycle but it remained robust after controlling for time of day and driving task duration. Both the number of JDS peaks counted for each trip and their duration declined in the presence of drowsiness feedback, indicating a dynamic pattern that is consistent with a genuine, entropy-reducing feedback mechanism (as distinct from random re-alerting) behind the observed effect. Its mechanisms and practical utility have yet to be fully explored. Direct examination of the alternative, random re-alerting explanation of this feedback effect is an important step for future research.