Browsing by Author "Leite, Harlei Miguel de Arruda"

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    Analysis of user Interaction with a brain-computer interface based on steady-state visually evoked potentials : case study of a game.
    (2018) Leite, Harlei Miguel de Arruda; Leite, Sarah Negreiros de Carvalho; Costa, Thiago Bulhões da Silva; Attux, Romis Ribeiro de Faissol; Hornung, Heiko Horst; Arantes, Dalton Soares
    This paper presents a systematic analysis of a game controlled by a Brain-Computer Interface (BCI) based on Steady-State Visually Evoked Potentials (SSVEP).The objective is to understand BCI systems from the Human-Computer Interface (HCI) point of view, by observing how the users interact with the game and evaluating how the interface elements influence the system performance. The interactions of 30 volunteers with our computer game, named “Get Coins,” through a BCI based on SSVEP, have generated a database of brain signals and the corresponding responses to a questionnaire about various perceptual parameters, such as visual stimulation, acoustic feedback, background music, visual contrast, and visual fatigue. Each one of the volunteers played one match using the keyboard and four matches using the BCI, for comparison. In all matches using the BCI, the volunteers achieved the goals of the game. Eight of them achieved a perfect score in at least one of the four matches, showing the feasibility of the direct communication between the brain and the computer. Despite this successful experiment, adaptations and improvements should be implemented to make this innovative technology accessible to the end user.
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    Space-time filter for SSVEP brain-computer interface based on the minimum variance distortionless response.
    (2021) Leite, Sarah Negreiros de Carvalho; Vargas, Guilherme Vettorazzi; Costa, Thiago Bulhões da Silva; Leite, Harlei Miguel de Arruda; Coradine, Luis Cláudius; Boccato, Levy; Soriano, Diogo Coutinho; Attux, Romis Ribeiro de Faissol
    Brain-computer interfaces (BCI) based on steady-state visually evoked potentials (SSVEP) have been increasingly used in different applications, ranging from entertainment to rehabilitation. Filtering techniques are crucial to detect the SSVEP response since they can increase the accuracy of the system. Here, we present an analysis of a space-time filter based on the Minimum Variance Distortionless Response (MVDR). We have compared the performance of a BCISSVEP using the MVDR filter to other classical approaches: Common Average Reference (CAR) and Canonical Correlation Analysis (CCA). Moreover, we combined the CAR and MVDR techniques, totalling four filtering scenarios. Feature extraction was performed using Welch periodogram, Fast Fourier transform, and CCA (as extractor) with one and two harmonics. Feature selection was performed by forward wrappers, and a linear classifier was employed for discrimination. The main analyses were carried out over a database of ten volunteers, considering two cases: four and six visual stimuli. The results show that the BCI-SSVEP using the MVDR filter achieves the best performance among the analysed scenarios. Interestingly, the system’s accuracy using the MVDR filter is practically constant even when the number of visual stimuli was increased, whereas degradation was observed for the other techniques.
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    Uso de vozes sintetizadas em ambientes virtuais de ensino a distância.
    (2014) Leite, Harlei Miguel de Arruda; Cinto, Tiago; Leite, Sarah Negreiros de Carvalho; Peixoto, Cecilia Sosa Arias; Arantes, Dalton Soares
    Com a evolução da tecnologia da informação, novas interfaces de comunicação homem-máquina passaram a ser desenvolvidas de forma muito eficiente. Uma área que passou por grandes modificações foi a de educação a distância. Antes restrita a correspondências, hoje ela dispõe de modernos ambientes virtuais de educação. Este trabalho busca avaliar um ambiente tridimensional de educação a distância que faz uso de sintetizadores de fala. Para tanto, metodologias de avaliação foram aplicadas para avaliar tanto o ambiente quanto a voz sintetizada, viabilizando o estudo da correlação entre a qualidade do ambiente e a qualidade da voz.
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    Virtual learning environments : proposals for authoring and visualization of educational content.
    (2014) Cinto, Tiago; Leite, Harlei Miguel de Arruda; Peixoto, Cecilia Sosa Arias; Arantes, Dalton Soares
    Heated debates involving reforms in the educational system are becoming more and more frequent in recent years. This is due to the increasingly evident shortcomings in the educational system and its difficulties to evolve at the same pace as technological development. The aim of this work is to present an analysis of the current engineering educational context and propose an interactive content authoring system as well as a virtual professor in an attempt to make learning experience richer and more motivating to students.