This study aims at designing and implementing a single channel stand-alone Brain-Controlled Switch (BCS) device, which records the electroencephalography (EEG) signals from the scalp using electrodes, amplifies it, eliminates interferences (associated with the EEG signals) and processes the EEG signals to extract and decode temporal signal features to determine user’s intention of regulating an external switch. The design of our “brain-controlled switch” device is implemented using a bio-potential amplifier and a microcontroller. The bio-potential amplifier amplifies the EEG signals to a level sufficient for processing, eliminates interferences and ensures patient safety. The microcontroller (dsPIC30F4013) digitizes the amplified and conditioned analog EEG signals from the bio-potential amplifier, extracts the desired signal features for decoding and prediction of user’s intention and accordingly operates the external switch. When the user concentrates on an external visual stimulus or performs externally triggered movement (hand movement or motor imagery movement), a reproducible pattern appears in user’s EEG frequency bands. The analysis of these patterns is used to decode and predict user’s intention to operate an external switch. To realize our “brain-controlled switch”, we explored two EEG sources: steady-state visually evoked potentials (SSVEP) and beta rebounds, which are patterns generated in the EEG frequency bands associated with focusing on an external visual stimulus or performing externally triggered movements. In case of SSVEP based brain controlled switch, a repetitive visual stimulus (LED flickering at a specified frequency) was used. When the user concentrates on the flickering LED, a dominant fundamental frequency (equivalent to the flickering frequency) appears in the spectral representation of the EEG signals recorded at occipital lobes. Our microcontroller implemented a digital band pass filter to extract the frequency band containing this fundamental frequency and continuously took an average of the amplitude power every predetermined time interval. Whenever the amplitude average power exceeded the preset power threshold the external switch was turned ON. A healthy subject participated in this study, and it took approximately 3.14 ± 1.81 seconds of active concentration for the subject to turn ON the switch in real time with a false positive rate of 1.17%. In case of beta rebound based brain controlled switch, the subject was instructed to perform a brisk hand movement following an external synchronization signal. Our design focused on the post-movement beta rebound which occurs after the cessation of the movement to operate the external switch. Our microcontroller in this case implemented a digital band pass filter to extract the beta band and continuously took an average of its amplitude power every predetermined time interval. Whenever the amplitude average power exceeded the preset power threshold the external switch was turned ON. It took approximately 12.23 ± 7.39 seconds of active urging time by the subject to turn ON the switch in real time with a false positive rate of 9.33%. Thus we have designed a novel stand-alone BCS device which operates an external switch by decoding and predicting user’s intentions.

A construção de modelos representa uma perspectiva interessante para buscar a compreensão sobre aspectos do comportamento humano. A partir de modelos do desempenho humano e do estudo das características do erro humano, este trabalho propõe o S. PERERE (Simulation of Performance in Error), um simulador computacional do comportamento humano cujo objetivo é produzir de forma aleatória estados de erro humano. O simulador recebe como entrada a especificação do comportamento a ser simulado e produz como saída o comportamento afetado pelo erro. Para a geração dos estados de erro o S. PERERE possui um mecanismo perturbador do comportamento e também um mecanismo de disparo das perturbações. A construção do simulador está baseada na arquitetura cognitiva ACT-R (Atomic Components of Thought – Rational). A utilização prevista do S. PERERE é seu acoplamento com simuladores de processos de forma a permitir a verificação do impacto dos erros humanos nestes processos. / The construction of models represents an interesting perspective to reach the understanding about human behaviour aspects. From human performance models and from the study of error characteristics, this work purposes the S.PERERE (Simulation of Performance in Error), a human behaviour computational simulator, which main objective is to produce, in a random way, human error states. The simulator receives, as entrance, the specification of the behaviour to be simulated, and produces, as output, the behaviour affected by the error. For the generation of error states, S.PERERE has a behaviour disturber mechanism and also a mechanism to start the perturbations. The construction of the simulator is based on ACT-R (Atomic Components of Thought – Rational) cognitive architecture. The use of S.PERERE is under its coupling to process simulators, allowing the verification of human errors impact on theses processes.

A construção de modelos representa uma perspectiva interessante para buscar a compreensão sobre aspectos do comportamento humano. A partir de modelos do desempenho humano e do estudo das características do erro humano, este trabalho propõe o S. PERERE (Simulation of Performance in Error), um simulador computacional do comportamento humano cujo objetivo é produzir de forma aleatória estados de erro humano. O simulador recebe como entrada a especificação do comportamento a ser simulado e produz como saída o comportamento afetado pelo erro. Para a geração dos estados de erro o S. PERERE possui um mecanismo perturbador do comportamento e também um mecanismo de disparo das perturbações. A construção do simulador está baseada na arquitetura cognitiva ACT-R (Atomic Components of Thought – Rational). A utilização prevista do S. PERERE é seu acoplamento com simuladores de processos de forma a permitir a verificação do impacto dos erros humanos nestes processos. / The construction of models represents an interesting perspective to reach the understanding about human behaviour aspects. From human performance models and from the study of error characteristics, this work purposes the S.PERERE (Simulation of Performance in Error), a human behaviour computational simulator, which main objective is to produce, in a random way, human error states. The simulator receives, as entrance, the specification of the behaviour to be simulated, and produces, as output, the behaviour affected by the error. For the generation of error states, S.PERERE has a behaviour disturber mechanism and also a mechanism to start the perturbations. The construction of the simulator is based on ACT-R (Atomic Components of Thought – Rational) cognitive architecture. The use of S.PERERE is under its coupling to process simulators, allowing the verification of human errors impact on theses processes.

Brain Computer Interface (BCI) technology can be important for those unable to communicate due loss of muscle control. The P300 Speller allows communication at a rate up to eight selections per minute. Given this relatively slow rate of communication highly accurate classification is of great importance. Previous studies have shown that alternative stimuli (e.g., faces) can improve BCI speed and accuracy. The present study uses two new alternative stimuli, locations and graspable tools in a two-stimulus paradigm. Functional MRI studies have shown that images of familiar locations produce brain responses in the parahippocampal place area and graspable tools produce brain responses in premotor cortex.The current study shows that location and tool stimuli produce unique brain responses that can be used for classification in the two-stimulus paradigm. This study shows proof of concept for using two unique stimuli to improve speed and accuracy of the P300 Speller.

The theory of Gestalt was proposed in the nineteenth century to explain and predict the way that people perceptually group visual elements, and it has been used to develop guidelines for designing visual computer interfaces. In this thesis we seek to extend the use of Gestalt principles to the design of haptic and visual-haptic displays. The thesis begins with a survey of Gestalt research into visual, auditory and haptic perception. From this survey the five most commonly found principles are identified as figure-ground, continuation, closure, similarity and proximity. This thesis examines the proposition that these five principles can be applied to the design of haptic interfaces. Four experiments investigate whether Gestalt principles of figure-ground, continuation, closure, similarity and proximity are applicable in the same way when people group elements either through their visual (by colour) or haptic (by texture) sense. The results indicate significant correspondence between visual and haptic grouping. A set of haptic design guidelines for haptic displays are developed from the experiments. This allows us to use the Gestalt principles to organise a Gestalt-Taxonomy of specific guidelines for designing haptic displays. The Gestalt-Taxonomy has been used to develop new haptic design guidelines for information displays.

No description available.

Self-paced Brain computer interface (SBCI) systems allow individuals with motor disabilities to use their brain signals to control devices, whenever they wish. These systems are required to identify the user’s “intentional control (IC)” commands and they must remain inactive during all periods in which users do not intend control (called “no control (NC)” periods). This dissertation addresses three issues related to the design of SBCI systems: 1) their presently high false positive (FP) rates, 2) the presence of artifacts and 3) the identification of a suitable evaluation metric. To improve the performance of SBCI systems, the following are proposed: 1) a method for the automatic user-customization of a 2-state SBCI system, 2) a two-stage feature reduction method for selecting wavelet coefficients extracted from movement-related potentials (MRP), 3) an SBCI system that classifies features extracted from three neurological phenomena: MRPs, changes in the power of the Mu and Beta rhythms; 4) a novel method that effectively combines methods developed in 2) and 3 ) and 5) generalizing the system developed in 3) for detecting a right index finger flexion to detecting the right hand extension. Results of these studies using actual movements show an average true positive (TP) rate of 56.2% at the FP rate of 0.14% for the finger flexion study and an average TP rate of 33.4% at the FP rate of 0.12% for the hand extension study. These FP results are significantly lower than those achieved in other SBCI systems, where FP rates vary between 1-10%. We also conduct a comprehensive survey of the BCI literature. We demonstrate that many BCI papers do not properly deal with artifacts. We show that the proposed BCI achieves a good performance of TP=51.8% and FP=0.4% in the presence of eye movement artifacts. Further tests of the performance of the proposed system in a pseudo-online environment, shows an average TP rate =48.8% at the FP rate of 0.8%. Finally, we propose a framework for choosing a suitable evaluation metric for SBCI systems. This framework shows that Kappa coefficient is more suitable than other metrics in evaluating the performance during the model selection procedure.

Individuals with severe physical impairments have a reduced ability to communicate through movement and speech. We investigated transcranial Doppler ultrasound as a potential measurement modality for a novel brain-computer interface. It was hypothesized that cognitive activity would result in detectable changes in cerebral blood flow velocity within the middle cerebral arteries. Nine able-bodied participants alternated between rest and two different mental activities - silent word generation and mental rotation. Two analyses were performed to assess the feasibility and practicality of a TCD-based brain-computer interface. Both mental activities were independently differentiated from rest with high accuracy. Intuitive time-domain features were sufficient for classification. Data transmission rate was quadrupled by differentiating all three classes simultaneously using shorter state durations. Transcranial Doppler ultrasound can be used to automatically detect cognitive activity and may be useful as the basis of a brain-computer interface.

Individuals with severe physical impairments have a reduced ability to communicate through movement and speech. We investigated transcranial Doppler ultrasound as a potential measurement modality for a novel brain-computer interface. It was hypothesized that cognitive activity would result in detectable changes in cerebral blood flow velocity within the middle cerebral arteries. Nine able-bodied participants alternated between rest and two different mental activities - silent word generation and mental rotation. Two analyses were performed to assess the feasibility and practicality of a TCD-based brain-computer interface. Both mental activities were independently differentiated from rest with high accuracy. Intuitive time-domain features were sufficient for classification. Data transmission rate was quadrupled by differentiating all three classes simultaneously using shorter state durations. Transcranial Doppler ultrasound can be used to automatically detect cognitive activity and may be useful as the basis of a brain-computer interface.

A commercially available brain-body interface, the `Cyberlink' which was developed by a Dr Andrew Junker, has been evaluated as a potential interface device for persons with a severe disability such as traumatic brain injury. The literature concerning brain computer interfaces and other input devices is surveyed and it is shown there is a need to investigate the Cyberlink as an assistive technology device for persons with a disability. The investigation was carried out in four phases, using forty-four persons with and without physical, mental and sensory impairments as participants. The first phase consisted of a survey of common assistive technology devices along with the Cyberlink. This demonstrated that many users were able to operate alternative devices. The second phase identified a group of distinct users that could only use a Cyberlink to both recreate and communicate with the outside world. These participants formed the focus group. A modified contextual inquiry and design was performed at the same time as the phase two studies. The data collected from the contextual inquiry and design drove the design for a communication application, developed in phase three, that gave the focus group the opportunity to select yes and no answers to questions. Phase four was the testing phase of the new yes / no application. This identified some design flaws that were addressed following a target acquisition study which showed that some paths in the design were difficult to steer through. New prototypes were created and tested using this data. The final yes / no program allowed the focus group to select yes and no answers on prompting, albeit with a les's than 100% success rate. Success appeared to depend on the focus group not beirighampered by the inconsistent debilitation of their injuries and medications. The utility of the Cyberlink for the focus group for recreating and performing elementary communication is thus demonstrated for occasions when settings are relevant, medications are not dampening bio-signals, and the inconsistencies of the brain injury allow them to control the cursor.