Chang S. Nam

Movement imagery-related lateralization of event-related (de)synchronization (ERD/ERS): Motor-imagery duration effects

OBJECTIVE To investigate movement imagery-related lateralization of event-related (de)synchronization (ERD/ERS) during two motor-imagery tasks with varying movement duration (brief versus continuous). METHODS Twelve subjects performed or kinesthetically imagined the indicated movement (left or right hand movement) for 1 s (brief) or 5 s (continuous) while electroencephalograms (EEGs) were recorded using 16 electrodes covering the sensorimotor cortex of the brain according to the modified 10-20 system. RESULTS Significant hemispheric differences were found between contralateral and ipsilateral area in mu ERD, mu ERS and beta ERD during both brief and continuous conditions, showing contralateral dominance of mu and beta ERD and ipsilateral dominance of mu ERS. Beta ERS showed a significant ipsilateral dominance only in the brief condition. Movement imagery duration influenced the lateralization of mu ERD, beta ERD, and beta ERS, but not mu ERS. CONCLUSIONS The results of this study will aid in clarifying movement-related lateralization in association with imagery tasks under varying movement duration. SIGNIFICANCE For designing an EEG-based brain-computer interface (BCI) for people with severe neuromuscular impairments, movement imagery-related lateralization can play a key role in utilizing motor-imagery tasks as a control or communication strategy.

A P300-Based Brain–Computer Interface: Effects of Interface Type and Screen Size

As a nonmuscular communication and control system for people with severe motor disabilities, brain–computer interface (BCI) has found several applications. Although a few empirical studies of BCI user performance do exist, little to no research has specifically evaluated the impact of contributing factors on user performance in the BCI applications. To that end, our within-subjects design compared the impact of two different types of interface (ABC interface vs. frequency-based interface) and three levels of screen size (computer monitor, global positioning system, and cell phone screen) of a P300-based BCI application, P300 Speller, on user performance (accuracy, information transfer rate, amplitude, and latency) and usage preference. Ten participants with neuromuscular disabilities such as amyotrophic lateral sclerosis and cerebral palsy and 10 nondisabled participants were asked to type six, 10-character phrases in the P300 Speller. The overall accuracy was 79.7% for the nondisabled participants and 28.7% for participants with motor disabilities. The results showed that interface type and screen size have significant effects on user performance and usage preference, with varying degree of impact to participants with and without motor disabilities. Specifically, participants typed significantly more accurately in frequency-based interface and computer monitor screen. The results of this study should provide invaluable insights to the future research of P300-based BCI applications.

The roles of sensory modalities in collaborative virtual environments (CVEs)

This study was conducted to assess the effects of sensorial modalities on user performance, perception, and behavior in collaborative virtual environments (CVEs). Participants played a CVE game, air hockey, together with a remote partner under different sensory modality conditions, depending on the type of sensory feedback provided: visual-only (V), visual-haptic (V+H), and visual-haptic-audio feedback (V+H+A). Three types of measurements were used as dependent variables: (1) task performance measured as playing time, (2) user perception including the sense of presence, the sense of togetherness, and perceived collaboration, and (3) behavior measurement including the amount of force applied and the mallet deviation. Results of the study indicated that the task performance, perception, and user behavior in CVEs can be affected due to supported sensory modalities. Therefore, the multiple sensory information types that are required to perform the task at hand should be provided to effectively support collaboration between people in CVEs. The outcomes of this research should have a broad impact on multimodal user interaction, including research on physiological, psychophysical, and psychological mechanisms underlying human perception on multisensory feedback in CVEs.

Evaluation of P300-Based Brain-Computer Interface in Real-World Contexts

Despite recent advances in brain-computer interface (BCI) development, system usability still remains a large oversight. The goal of this study was to investigate the usability of a P300-based BCI system, P300 Speller, by assessing how background noise and interface color contrast affect user performance and BCI usage preference. Fifteen able-bodied participants underwent a 2 (low and high interface color contrast) × 3 (low, medium, and high background noise level) within-subjects design experiment, in which participants were asked to type six 10-character phrases in the P300 Speller paradigm. The overall accuracy in the study was 80.2%. Participants showed higher accuracy, higher information transfer rate, bigger amplitude, and smaller latency in the high interface color contrast condition than in the low contrast condition. Participants had better performance in the noisy condition than in the quiet condition, but the background noise effects were not statistically significant in the present study. These results should give some insight to the real-world applicability of the current P300 Speller as a nonmuscular communication system, especially for individuals with severe neuromuscular disabilities.

Acceptance of Assistive Technology by Special Education Teachers: A Structural Equation Model Approach

To investigate the acceptance of assistive technology (AT) by special education teachers, the present study developed and tested hypothesized relationships among key determinants of AT acceptance such as the facilitating condition, perceived ease of use, computer self-efficacy, result demonstrability, perceived usefulness, and behavioral intention. Results from analysis of data collected from a number of special education teachers in schools for the visually and/or auditory impaired confirmed the effects hypothesized in our conceptual model of AT acceptance. In particular, perceived usefulness was a dominant factor affecting AT usage. Facilitating condition was strongly related to perceived ease of use, whereas perceived ease of use had a significant effect on computer self-efficacy. This study also found the importance of result demonstrability factor, which had significant effects on both computer self-efficacy and perceived usefulness. This study expanded and enriched a traditional technology acceptance model by further investigating determinants associated with the acceptance of AT by special education teachers for the blind and/or the deaf. In addition, the results of the present study should provide some insights into the understanding of AT acceptance and the decisions of AT utilization, as well as its distribution and training.

Effects of Luminosity Contrast and Stimulus Duration on User Performance and Preference in a P300-Based Brain–Computer Interface

Brain–computer interfaces (BCI) have potential to provide a new channel of communication and control for people with severe motor disabilities. Although many empirical studies exist, few have specifically evaluated the impact of contributing factors on user performance and perception in BCI applications, especially for users with motor disabilities. This article reports the effects of luminosity contrast and stimulus duration on user performance and usage preference in a P300-based BCI application, P300 Speller. Ten participants with neuromuscular disabilities (amyotrophic lateral sclerosis and cerebral palsy) and 10 able-bodied participants were asked to spell six 10-character phrases in the P300 Speller. The overall accuracy was 76.5% for the able-bodied participants and 26.8% for participants with motor disabilities. The results showed that luminosity contrast and stimulus duration have significant effects on user performance. In addition, participants preferred high luminosity contrast with middle or short stimulus duration. However, these effects on user performance and preference varied for participants with and without motor disabilities. The results also indicated that although most participants with motor disabilities can establish BCI control, BCI illiteracy does exist. These results of the study should provide insights into the future research of the BCI systems, especially the real-world applicability of the BCI applications as a nonmuscular communication and control system for people with severe motor disabilities.

Severe motor disability affects functional cortical integration in the context of brain–computer interface (BCI) use

The purpose of this study was to investigate cortical interaction between brain regions in people with and without severe motor disability during brain–computer interface (BCI) operation through coherence analysis. Eighteen subjects, including six patients with cerebral palsy (CP) and three patients with amyotrophic lateral sclerosis (ALS), participated. The results showed (1) the existence of BCI performance difference caused by severe motor disability; (2) different coherence patterns between participants with and without severe motor disability during BCI operation and (3) effects of motor disability on cortical connections varying in the brain regions for the different frequency bands, indicating reduced cortical differentiation and specialisation. Participants with severe neuromuscular impairments, as compared with the able-bodied group, recruited more cortical regions to compensate for the difficulties caused by their motor disability, reflecting a less efficient operating strategy for the BCI task. This study demonstrated that coherence analysis can be applied to examine the ways cortical networks cooperate with each other during BCI tasks. Practitioner Summary: Few studies have investigated the electrophysiological underpinnings of differences in BCI performance. This study contributes by assessing neuronal synchrony among brain regions. Our findings revealed that severe motor disability causes more cortical areas to be recruited to perform the BCI task, indicating reduced cortical differentiation and specialisation.

Elicitation of Haptic User Interface Needs of People with Low Vision

Various assistive technologies such as haptic technology are used to help people with visual impairments comprehend complex information. Yet there is likely to be a misconception that users with the same disability category share the same user interface needs; furthermore, the majority of the literature has been oriented toward total blindness rather than low vision, possibly leading to dissatisfaction with assistive technologies and discontinuation of its use by those with low vision. The aim of this article is to advance the understanding of the needs of those with low vision especially in relation to haptic-incorporated multimodal user interfaces. A scenario-based, participatory design approach was used to explore their needs. A total of 19 user needs were systematically documented under three categories: audition (n = 5), touch (n = 11), and vision (n = 3). This article focuses on qualitatively exploring their needs and theoretically interpreting the needs in the light of previous studies.

The Effects of Haptic Feedback and Visual Distraction on Pointing Task Performance

Previous research has not fully examined the effect of additional sensory feedback, particularly delivered through the haptic modality, in pointing task performance with visual distractions. This study examined the effect of haptic feedback and visual distraction on pointing task performance in a 3D virtual environment. Results indicate a strong positive effect of haptic feedback on performance in terms of task time and root mean square error of motion. Level of similarity between distractor objects and the target object significantly reduced performance, and subjective ratings indicated a sense of increased task difficulty as similarity increased. Participants produced the best performance in trials where distractor objects had a different color but the same shape as the target object and constant haptic assistive feedback was provided. Overall, this study provides insight toward the effect of object features and similarity and the effect of haptic feedback on pointing task performance.

The Human Factors and Ergonomics of P300-Based Brain-Computer Interfaces

Individuals with severe neuromuscular impairments face many challenges in communication and manipulation of the environment. Brain-computer interfaces (BCIs) show promise in presenting real-world applications that can provide such individuals with the means to interact with the world using only brain waves. Although there has been a growing body of research in recent years, much relates only to technology, and not to technology in use—i.e., real-world assistive technology employed by users. This review examined the literature to highlight studies that implicate the human factors and ergonomics (HFE) of P300-based BCIs. We assessed 21 studies on three topics to speak directly to improving the HFE of these systems: (1) alternative signal evocation methods within the oddball paradigm; (2) environmental interventions to improve user performance and satisfaction within the constraints of current BCI systems; and (3) measures and methods of measuring user acceptance. We found that HFE is central to the performance of P300-based BCI systems, although researchers do not often make explicit this connection. Incorporation of measures of user acceptance and rigorous usability evaluations, increased engagement of disabled users as test participants, and greater realism in testing will help progress the advancement of P300-based BCI systems in assistive applications.