RESUMO
The impact of binaural beats (BBs) on human cognition and behavior remains and various methods have been used to measure their effect, including neurophysiological, psychometric, and human performance evaluations. The few approaches where the level of neural synchronicity and connectivity were measured by neuroimaging techniques have only been undertaken in spontaneous mode. The present research proposes an approach based on the oddball paradigm to study BB effect by estimating the level of attention induced by BBs. Evoked activity of 25 young adults between 19 and 24 years old with no hearing impairments nor clinical neurological history were analyzed. The experiment was conducted in two different sessions of 24.5 min. The first part consisted of 20-min BB stimulation in either theta (BBθ) or beta (BBß). After the BB stimulation, an oddball paradigm was applied in each BB condition to assess the attentional effect induced by BBs. Attention enhancement is expected for BBß with respect to BBθ. Target event related potentials (ERPs) were mainly analyzed in the time and time-frequency domains. The frequency analysis was based on continuous wavelet transform (CWT), event-related spectral perturbation (ERSP), and inter-trial phase coherence (ITPC). The study revealed that the P300 component was not significantly different between conditions (BBθ vs. BBß). However, the target grand average ERP in BBθ condition was mainly composed of 8 Hz-frequency components, appearing before 400 ms post-stimulus, and mainly on the centro-parietal regions. In contrast, the target grand average ERP in BBß condition was mainly composed of frequency components below 6 Hz, mainly appearing at 400 ms post-stimulus on the parieto-occipital regions. Furthermore, ERPs in the BBθ condition were more phase locked than the BBß condition.
Assuntos
Eletroencefalografia , Potenciais Evocados Auditivos , Adulto Jovem , Humanos , Adulto , Potenciais Evocados Auditivos/fisiologia , Estimulação Acústica/métodos , Eletroencefalografia/métodos , Potenciais Evocados/fisiologia , AtençãoRESUMO
Neural responses of oddball tasks can be used as a physiological biomarker to evaluate the brain potential of information processing under the assumption that the differential contribution of deviant stimuli can be assessed accurately. Nevertheless, the non-stationarity of neural activity causes the brain networks to fluctuate hugely in time, deteriorating the estimation of pairwise synergies. To deal with the time variability of neural responses, we have developed a piecewise multi-subject analysis that is applied over a set of time intervals within the stationary assumption holds. To segment the whole stimulus-locked epoch into multiple temporal windows, we experimented with two approaches for piecewise segmentation of EEG recordings: a fixed time-window, at which the estimates of FC measures fulfill a given confidence level, and variable time-window, which is segmented at the change points of the time-varying classifier performance. Employing the weighted Phase Lock Index as a functional connectivity metric, we have presented the validation in a real-world EEG data, proving the effectiveness of variable time segmentation for connectivity extraction when combined with a supervised thresholding approach. Consequently, we performed a piecewise group-level analysis of electroencephalographic data that deals with non-stationary functional connectivity measures, evaluating more carefully the contribution of a link node-set in discriminating between the labeled oddball responses.
RESUMO
Introdução: O tempo de reação é uma medida que indica o tempo que uma pessoa leva para iniciar um movimento. Há situações em que o tempo de reação encontra-se alterado, comprometendo o processamento da informação, com diminuição na detecção, transmissão e processamento dos estímulos. Objetivo: Investigar o tempo de reação visual em acadêmicos antes e após atividades avaliativas, nas diversas disciplinas. Metodologia: 50 acadêmicos foram analisados antes e após atividades avaliativas por meio do tempo de reação simples e paradigma oddball. Resultados: Com relação ao tempo de reação simples, o tempo de reação visual antes das atividades avaliativas foi menor que após, em contradição com o paradigma oddball. Verificou-se que a média geral do tempo de reação simples para prova prática foi maior comparado às demais, já no paradigma oddball verificou-se que a média geral para apresentação de seminário foi maior, comparado às demais. Conclusão: Diferenças significativas no tempo de reação simples e tempo de reação segundo paradigma oddball foram encontrados entre acadêmicos antes e após atividades avaliativas. Porém no tempo de reação simples foram encontrados valores menores antes das atividades, quando comparados com após, e o contrário foi encontrado no paradigma oddball. (AU)
Introduction: Reaction time is a measure of how long a person takes to start a movement. There are situations in which the reaction time is altered, compromising the information processing, with a decrease in the detection, transmission and processing of the stimuli. Objective: To investigate the time of visual reaction in academics before and after evaluative activities in different disciplines. Methodology: 50 academics were analyzed before and after evaluative activities through simple reaction time and oddball paradigm. Results: Relative to the time of simple reaction, the visual reaction time before the evaluative activities was smaller than after, in contradiction with the oddball paradigm. It was verified that the general mean of the simple reaction time for practical test was higher compared to the others, already in the oddball paradigm it was verified that the general average for seminar presentation was higher, compared to the others. Conclusion: Significant differences in the time of simple reaction and reaction time according to the oddball paradigm were found among academics before and after evaluative activities. However, in the simple reaction time smaller values were found before the activities, when compared with after, and the opposite was found in the oddball paradigm. (AU)
Assuntos
Humanos , Tempo de Reação , Estudantes , Processamento Eletrônico de Dados , MovimentoRESUMO
This paper presents an application developed on the BCI2000 platform which reduces the average spelling time per symbol on the Donchin speller. The motivation was to reduce the compromise between spelling rate and spelling accuracy due to the large amount of responses required in order to perform coherent average techniques. The methodology was made under a Bayesian approach which allows calculation of each target's class posterior probability. This result indicates the probability of each response of belonging to the infrequent class. When there is enough evidence to make a decision the system stops the stimulation process and moves on with the next symbol, otherwise it continues stimulating the user until it finds the selected letter. The average spelling rate, after using the proposed methodology with 14 healthy users and a maximum number of 5 stimulation sequences, was of 6.1 ± 0.63 char/min, compared to a constant rate of 3.93 char/min with the standard system.
Este trabajo presenta una aplicación desarrollada sobre la plataforma BCI2000 que disminuye el tiempo promedio de selección de los símbolos del deletreador de Donchin. La motivación consistió en reducir el compromiso entre la taza de deletreo y la precisión correspondiente, la cual surge como consecuencia de la gran cantidad de respuestas necesarias para realizar técnicas de promediación coherente. La metodología propuesta se basa en un enfoque Bayesiano que permite calcular la probabilidad posterior asociada con la clasificación de cada objetivo, resultado que indica la evidencia que presentan las respuestas de pertenecer a la clase infrecuente. Cuando existe evidencia suficiente para tomar una decisión, el sistema detiene el proceso de estimulación y continúa con el siguiente símbolo, de lo contrario permanece estimulando al usuario hasta conseguir identificar la letra seleccionada. Después de utilizar la metodología propuesta sobre los registros de 14 usuarios sanos con un número máximo de 5 series de estimulación, el tiempo promedio de deletreo reportado es de 6.1 ± 0.63 letras/min, el cual es comparado con una taza constante de 3.93 letras/min obtenido con un sistema convencional.