Frequência Alfa na meditação Gurdjieff / Alpha Frequency in Gurdjieff Meditation

Introdução: a meditação é uma prática que visa regular o estado mental e as emoções, podendo induzir a estados alterados de consciência. Dentre inúmeras técnicas de meditação, o trabalho proposto por George I. Gurdjieff, inclui práticas voltadas para o recolhimento da atenção e o equilíbrio entre a atividade do corpo, da mente e do sentimento. Estudos realizados com eletroencefalografia (EEG), avaliando o estado meditativo em geral, demonstraram um padrão cerebral caracterizado pelo aumento da amplitude dos ritmos eletroencefalográficos alfa e teta, bem como diferenças na atividade alfa entre a meditação e o relaxamento. Entretanto, isto não está caracterizado em meditadores da linha de G.I. Gurdjieff, que praticam, além de meditações sentadas, exercícios corporais acompanhados de uma música própria e exercícios de atenção durante a vida diária. Objetivo: comparar a atividade cerebral da frequência alfa durante os estágios de meditação e relaxamento e avaliar as diferenças entre as regiões frontal, central e occipital nesses dois estados, em meditadores experientes do grupo Gurdjieff, de Salvador-Bahia-Brasil. Metodologia: a coleta da atividade cerebral dos 8 voluntários foi realizada através do EEG. O protocolo de coleta adotado foi de 6 minutos de relaxamento e 12 minutos de meditação. Resultados: foi encontrado aumento significativo da potência alfa durante a meditação, quando comparada ao relaxamento. As regiões frontal e central não apresentaram diferenças entre si para a potência alfa, enquanto a região occipital apresentou aumento da potência alfa em comparação com as regiões frontal e central. Existe um aumento da densidade de alfa durante a meditação em todas as regiões cerebrais testadas, com maior densidade na região occipital. Conclusão: A frequência alfa comporta-se de forma diferente durante a meditação, comparada ao relaxamento, com um aumento da densidade de potência durante o estado meditativo em todas as regiões avaliadas, sendo a região occipital a que apresentou maior potência.

Introduction: meditation is a practice that aims to regulate the mental state and emotions, and can induce altered states of consciousness. Among numerous meditation techniques, the work proposed by George I. Gurdjieff, includes an attempt to balance activities from the body, the mind and the feelings. Studies conducted with electroencephalography (EEG), evaluating the meditative tate, demonstrated a brain pattern characterized by increased alpha and theta amplitude, as well as differences in alpha activity between meditation and relaxation. However, this is not characterized in Gurdjieff meditators, which practice beyond sitted meditations, body exercises with music, and attentional exercises during everyday life. Objective: comparing the brain activity of the alpha power during the meditation and relaxation stages and evaluate the differences between the frontal, central and occipital regions in these two states, in experienced meditators from the Gurdjieff group, in Salvador-Bahia-Brazil. Methodology: the data collection of the brain activity from 8 volunteers was performed by EEG. The collection protocol adopted was 6 minutes of relaxation and 12 minutes of meditation. Results: a significant increase in alpha power was found during meditation, when compared to relaxation. The frontal and central regions showed no differences between them for alpha power, while the occipital region showed an increase in alpha power compared to the frontal and central regions. Conclusion: the alpha frequency behaves differently during meditation, compared to relaxation, with an increase in alpha density during the meditative state in all evaluated regions, with the occipital region being the most potent.

Electro-deposited Nanoporous Platinum Electrode for EEG Monitoring

BACKGROUND: One of the key issues in electroencephalogram (EEG) monitoring is accurate signal acquisition with less cumbersome electrodes. In this study, the L2 phase electro-deposited nanoporous platinum (L2-ePt) electrode is introduced, which is a new type of electrode that utilizes a stable nanoporous platinum surface to reduce the skin-electrode impedance. METHODS: L2-ePt electrodes were fabricated using electro-deposition technique. Then, the effect of the nanoporous surface on the surface roughness and the electrode impedance were observed from the L2-ePt electrodes and the flat platinum (FlatPt) electrode. The skin-electrode impedances of the L2-ePt electrodes, a gold cup electrode, and the FlatPt electrode were evaluated when placed on the hairy occipital area of the head in ten subjects. For the validation of using the L2-ePt electrode, a correlational analysis of the alpha rhythms was performed in the same subjects for simultaneous EEG recordings using the L2-ePt and clinically-used EEG electrodes. RESULTS: The results indicated that the L2-ePt electrode with a roughness factor of 200 had the lowest mean impedance performance. Moreover, the proposed L2-ePt electrode showed a significantly lower mean skin-electrode impedance than the FlatPt electrode. Finally, the EEG signal quality recorded by the L2-ePt electrode (r = 0.94) was comparable to that of the clinically-used gold cup electrode. CONCLUSION: Based on these results, the proposed L2-ePt electrode is suitable for use in various high-quality EEG applications.

Alpha band EEG coherence in healthy nonagenarians / Coerência da banda alfa do EEG em nonagenários saudáveis

ABSTRACT Electroencephalographic (EEG) coherence is a parameter that enables evaluation of cerebral connectivity. It may be related to the functional state of the brain. In the elderly, it may reflect the neuronal loss caused by aging. Objective To describe characteristics of coherence in nonagenarians. Methods We evaluated interhemispheric coherence for the alpha band in 42 cognitively normal individuals aged 90 to 101 years. Coherence values in the occipital electrode (O1O2), in the resting state with closed eyes, were calculated by means of spectral analysis using digital EEG EMSA 32 channels, 12 bits and a frequency of 200 Hz. Results The mean coherence value for the alpha band at O1O2 was 0.65 (SD 0.13). No significant differences were found between men and women. Conclusions The findings from this study did not show any decrease in interhemispheric coherence for the alpha band in cognitively normal nonagenarians. This may be useful as a standard value for this age group.

RESUMO A coerência é um parâmetro que permite avaliar a conectividade cerebral, podendo se relacionar com o estado funcional do cérebro. Especialmente nos idosos, pode refletir a perda neuronal decorrente do envelhecimento. Objetivo Descrever características da coerência em nonagenários. Métodos Avaliamos a coerência interhemisferica para a banda alfa em 42 indivíduos cognitivamente normais entre 90 e 101 anos. Foram calculados através da análise espectral o valor da coerência nos eletrodos O1O2, em estado de repouso e olhos fechados, com EEG digital 32 canais marca EMSA 12 bits e frequência de amostragem 200 hz. Resultados O valor médio da coerência para a banda alfa entre O1O2 foi de 0,65 (DP 0,13). Não encontramos diferenças significativas entre homens e mulheres. Conclusão Os achados desse estudo não evidenciam diminuição da coerência interhemisferica para a banda alfa nos eletrodos O1O2 em nonagenários saudáveis e cognitivamente normais, podendo indicar um valor padrão para essa faixa etária.

Correlation between Quantitative Electroencephalogram Findings and Neurocognitive Functions in Patients with Obsessive-Compulsive Disorder and Schizophrenia

OBJECTIVES: Obsessive-compulsive disorder (OCD) and schizophrenia have many common clinical and neurocognitive features. However, not all of them share the same underlying mechanism. The aim of this study was to discover evidences that indicate a pathophysiological mechanism specific to OCD by comparing correlations of quantitative electroencephalography (QEEG) patterns and neurocognitive function in patients with OCD and schizophrenia. METHODS: Resting-state QEEG data of total 265 patients were acquired retrospectively and parameters such as absolute power, relative power and peak frequency were analyzed from the data. Stroop test and Trail Making Test results as well as demographic features were reviewed for this study. The correlation of neurocognitive functions and brain electrical activities in each group were assessed and compared by correlation analysis. RESULTS: Compared with the OCD group, the schizophrenia group performed poorly in neurocognitive tests. Mean values of QEEG parameters in patients with OCD and schizophrenia did not show significant differences. Both absolute and relative power of alpha rhythm in central and frontal regions showed significant positive correlation with Stroop test results in OCD patients. CONCLUSIONS: Findings in this study shows distinctive correlations between frontal executive dysfunction and frontal alpha rhythm in the OCD patients, both of which might be a candidate for endophenotype underlying obsessive rumination.

Cortical activity in tinnitus patients and its modification by phonostimulation

OBJECTIVE: The goal of this study was to observe spontaneous cortical activity and cortical activity modulated by tinnitus-matched sound in tinnitus patients and healthy subjects with no otoneurologic symptoms. METHOD: Data were prospectively collected from 50 tinnitus patients and 25 healthy subjects. Cortical activity was recorded in all subjects with eyes closed and open and during photostimulation, hyperventilation and acoustic stimulation using 19-channel quantitative electroencephalography. The sound applied in the tinnitus patients was individually matched with the ability to mask or equal the tinnitus. The maximal and mean amplitude of the delta, theta, alpha and beta waves and the type and amount of the pathologic EEG patterns were noted during each recording. Differences in cortical localization and the influence of sound stimuli on spontaneous cortical activity were evaluated between the groups. RESULTS: The tinnitus group exhibited decreased delta activity and increased alpha and beta activity. Hyperventilation increased the intensity of the differences. The tinnitus patients had more sharp-slow waves and increased slow wave amplitude. Sound stimuli modified the EEG recordings; the delta and beta wave amplitudes were increased, whereas the alpha-1 wave amplitude was decreased. Acoustic stimulation only slightly affected the temporal region. CONCLUSION: Cortical activity in the tinnitus patients clearly differed from that in healthy subjects, i.e., tinnitus is not a “phantom” sign. The changes in cortical activity included decreased delta wave amplitudes, increased alpha-1, beta-1 and beta-h wave amplitudes and pathologic patterns. Cortical activity modifications occurred predominantly in the temporal region. Acoustic stimulation affected spontaneous cortical activity only in tinnitus patients, and although the applied sound was individually matched, the pathologic changes were only slightly improved. .

Analysis of characteristics of alpha electroencephalogram during the interaction between emotion and cognition based on Granger causality / 生物医学工程学杂志

Studying the functional network during the interaction between emotion and cognition is an important way to reveal the underlying neural connections in the brain and nowadays, it has become a hot topic in cognitive neuroscience. Granger causality (GC), based on multivariate autoregressive (MVAR) model, and being able to be used to analyse causal characteristic of brain regions has been widely used in electroencephalography (EEG) in event-related paradigms research. In this study, we recorded the EEGs from 13 normal subjects (6 males and 7 females) during emotional face search task. We utilized Granger causality to establish a causal model of different brain areas under different rhythms at specific stages of cognition, and then convinced the brain dynamic network topological properties in the process of emotion and cognition. Therefore, we concluded that in the alpha band, (1) negative emotion face induced larger causal effects than positive ones; (2) 100-200ms emotional signal was the most prominent ones while 300-400ms and 700-800ms would take the second place; (3) The rear brain region modulated the front in the process of causal modulation; (4) The frontal and pillow area involved in the brain causal modulation as a key brain area; and (5) Negative partiality existed in the information processing, especially during 0-100ms after the negative expression stimulation.

Alzheimer's disease qEEG: spectral analysis versus coherence. which is the best measurement? / EEGq na doença de Alzheimer: análise espectral versus coerência. O que é melhor?

There is evidence in electroencephalography that alpha, theta and delta band oscillations reflect cognitive and memory performances and that quantitative techniques can improve the electroencephalogram (EEG) sensitivity. This paper presents the results of comparative analysis of qEEG variables as reliable markers for Alzheimer's disease (AD). We compared the sensitivity and specificity between spectral analysis (spectA) and coherence (Coh) within the same group of AD patients. SpectA and Coh were calculated from EEGs of 40 patients with mild to moderate AD and 40 healthy elderly controls. The peak of spectA was smaller in the AD group than in controls. AD group showed predominance of slow spectA in theta and delta bands and a significant reduction of inter-hemispheric Coh for occipital alpha 2 and beta 1 and for frontal delta sub-band. ROC curve supported that alpha band spectA was more sensitive than coherence to differentiate controls from AD.

Há evidências de que as oscilações das bandas teta, alfa e delta no eletroencefalograma podem refletir diferenças na cognição e memória; a sensibilidade deste método diagnóstico pode ser melhorada por técnicas de quantificação. Comparamos a sensibilidade e especificidade entre a análise espectral (spectA) e coerência (Coh) dentro do mesmo grupo de pacientes com doença de Alzheimer (DA) e contra um grupo controle. SpectA e Coh foram calculadas a partir de EEGs de 40 pacientes com DA leve a moderada e 40 idosos saudáveis. O pico do espectro foi menor no grupo DA que nos controles. O grupo DA também apresentou um espectro mais lento nas bandas teta e delta e menor coerência inter-hemisférica para as sub-bandas alfa 2 e beta 1 posterior e delta frontal. A curva ROC suporta que a análise espectral da banda alfa foi mais sensível que a coerência para diferenciar controles de DA.

EEG changes during sequences of visual and kinesthetic motor imagery / Alterações no EEG durante sequencias de imagética motora visual e cinestésica

The evoked cerebral electric response when sequences of complex motor imagery (MI) task are executed several times is still unclear. This work aims at investigating the existence of habituation in the cortical response, more specifically in the alpha band peak of parietal and occipital areas (10-20 international system electroencephalogram, EEG, protocol). The EEG signals were acquired during sequences of MI of volleyball spike movement in kinesthetic and visual modalities and also at control condition. Thirty right-handed male subjects (18 to 40 years) were assigned to either an 'athlete' or a 'non-athlete' group, both containing 15 volunteers. Paired Wilcoxon tests (with α=0.05) indicates that sequential MI of complex tasks promotes cortical changes, mainly in the power vicinity of the alpha peak. This finding is more pronounced along the initial trials and also for the athletes during the modality of kinesthetic motor imagery.

A resposta elétrica cerebral evocada quando sequencias de imagética motora (MI) de tarefas complexas são executadas seguidamente no tempo permanecem desconhecidas. Este trabalho objetivou investigar a existência de habituação da resposta cortical, mais especificamente na banda do pico de alfa de áreas parietais e occipitais (sistema internacional 10-20, eletroencefalograma, protocolo de EEG). Os sinais de EEG foram adquiridos durante sequências de MI do movimento de ataque do voleibol nas modalidades cinestésica e visual, e também em condição de controle. Trinta voluntários adultos (entre 18 e 40 anos), destros, do gênero masculino foram agrupados como 'atletas' ou 'não-atletas', sendo cada grupo composto de 15 voluntários. Testes pareados de Wilcoxon (com α=0.05) indicaram que a MI sequencial de tarefas complexas promoveram alterações nas respostas corticais, mais especificamente na região ao redor do pico de alfa. Este achado foi mais pronunciado ao longo dos trechos iniciais e também nos atletas durante a modalidade cinestésica de imagética motora.

Effect of aerobic training on EEG alpha asymmetry and depressive symptoms in the elderly: a 1-year follow-up study

The effect of physical exercise on the treatment of depressive elderly adults has not been investigated thus far in terms of changes in cortical hemispheric activity. The objective of the present study was to identify changes in depressive symptoms, quality of life, and cortical asymmetry produced by aerobic activity. Elderly subjects with a diagnosis of major depressive disorder (DSM-IV) were included. Twenty patients (70 percent females, 71 ± 3 years) were divided into an exercise group (pharmacological treatment plus aerobic training) and a control group (undergoing pharmacological treatment) in a quasi-experimental design. Pharmacological treatment was maintained stable throughout the study (antidepressants and anxiolytics). Subjects were evaluated by depression scales (Beck Depression Inventory, Hamilton Depression Rating Scale, Montgomery-Asberg Depression Rating Scale) and the Short Form Health Survey-36, and electroencephalographic measurements (frontal and parietal alpha asymmetry) before and after 1 year of treatment. After 1 year, the control group showed a decrease in cortical activity on the right hemisphere (increase of alpha power), which was not observed in the exercise group. The exercise group showed a significant decrease of depressive symptoms, which was not observed in the control group. This result was also accompanied by improved treatment response and remission rate after 1 year of aerobic exercise associated with treatment. This study provides support for the effect of aerobic training on alpha activity and on depressive symptoms in elderly patients. Exercise facilitates the treatment of depressive elderly adults, leading to clinical and physical improvement and protecting against a decrease in cortical activity.

The continuous analysis of EEG's alpha wave by morlet wavelet transform / 生物医学工程学杂志

Complex Morlet wavelets, as a wavelet function, is most commonly used in the time-frequency analysis of EEG signal and in the extraction of the instantaneous power and phase. This article explains how to use the Morlet wavelet transform for obtaining EEG's alpha wave energy distribution over time, and how to use the EEG data of mental arithmetic experiment for obtaining the changes of the alpha wave duration.

EEG alpha peak frequency analysis during memorizing of figures in patients with mild cognitive impairment / Análise do pico de frequência alfa do EEG durante a memorização de figuras em pacientes com comprometimento cognitivo leve

OBJECTIVE: To investigate spectral analysis of electroencephalograms (EEG) for the alpha frequency band during rest and cognitive stimulation in healthy adults and individuals with mild cognitive impairment. METHOD: We analyzed 56 EEGs from 28 patients, 7 men and 21 women, 12 of whom (40 percent) were controls, 16 patients with mild cognitive impairment (60 percent). Ages ranged from 61 to 83 years. All individuals were patients in the Psycho-geriatric Out-patients Clinic of LIM-27, of the Psychiatric Institute of the Clinicas Hospital of the Faculty of Medicine of the University of São Paulo, IPq-HCFMUSP, between 2004 and 2007. Each patient underwent two exams with an interval of at least six months between them. During the exam, performed after a period of wakefulness and rest, the patients memorized series of pictures. RESULTS: Analysis of spectral potential both at rest and during the memorizing task showed no statistical differences between baseline and final recordings. CONCLUSION: Spectral analysis of EEGs showed coherent results with the clinical stability of the patients evaluated but was unable to distinguish between the control group and patients with MCI. Future studies should include a larger sample and a longer follow up.

OBJETIVO: Realizar a análise espectral da banda de frequência alfa do EEG em adultos saudáveis, com comprometimento cognitivo leve (CCL), durante o repouso e a estimulação cognitiva. MÉTODO: Analisamos 56 EEGs de 28 pacientes, 7 homens e 21 mulheres, 12 dos quais (40 por cento) controles, 16 pacientes com CCL (60 por cento), com idades entre 61 a 83 anos.Todos os pacientes foram atendidos no serviço de psicogeriatria do LIM 27, do Instituto de Psiquiatria da Faculdade de Medicina da USP,entre os anos de 2004 a 2007, sendo que cada paciente realizou 2 exames com intervalo de 6 meses entre eles. Os registros dos EEGs foram realizados em repouso e durante a realização de atividade de memorização de figuras. RESULTADOS: A analise espectral durante o repouso e a tarefa de memorização não mostraram diferenças estatísticas entre os EEGs iniciais e finais. CONCLUSÃO: A análise espectral dos EEGs mostrou-se coerente com a estabilidade clínica dos dois grupos, no entanto não foi capaz de distinguir o grupo controle do grupo CCL. Estudos futuros deverão incluir um maior número de indivíduos por um tempo maior de seguimento.

Entropy analysis of the EEG alpha activity in depression patients / 生物医学工程学杂志

The alpha rhythm in electroencephalograph has been associated with the mental state of the brain. The aim of the present study was to analyze the complexity of the alpha activity in depression patients by Renyi entropy (RE) under two conditions, i.e., resting with eyes closed followed by a simple mental arithmetic. The EEGs were recorded in 20 depression patients and 20 age-matched control subjects. Results showed that the alpha activity of depression patients is more complex during resting and is more regular during the mental arithmetic than that of the controls. RE analysis can well characterize the alpha activity in depression patients and could be a valuable tool to study cognitive process and also a potential effective approach for the diagnosis of depression.

Alpha absolute power: motor learning of practical pistol shooting / Potência absoluta de alfa: aprendizagem motora do tiro prático de pistola

The present study aimed at investigating changes in behavior (shooting precision) and electrophysiological variables (absolute alpha power) during the motor learning of practical pistol shooting. The sample was composed of 23 healthy subjects, right-handed, male, between 18 and 20 years of age. The task consisted of four learning blocks. A One-way ANOVA with repeated measures and a post hoc analysis were employed to observe modifications on behavioral and electrophysiological measures (p<0.05). The results showed significative differences between blocks according to motor learning, and a significant improvement in shooting's accuracy from both blocks. It was observed a decrease in alpha power in all electrodes examined during task execution when compared with baseline and learning control blocks. The findings suggest that alpha power decreases as the function of the motor learning task when subjects are engaged in the motor execution.

O presente estudo teve por objetivo investigar alterações nas variáveis comportamentais (precisão do tiro) e eletrofisiológicas (potência absoluta de alfa) durante o aprendizado motor do tiro prático de pistola. A amostra constituiu-se de 20 sujeitos saudáveis, destros, sexo masculino, faixa etária entre 18 e 20 anos. A tarefa consistiu de quatro blocos de aprendizagem. A análise estatística das variáveis comportamentais e eletrofisiológicas foram realizadas por meio de uma ANOVA one-way e uma análise post hoc (p<0,05). Os resultados demonstraram diferenças significativas entre os blocos em função do aprendizado motor, bem como uma sensível melhora na precisão do tiro de ambos os blocos. Foi observada uma diminuição na potência de alfa em todos os eletrodos analisados durante a execução da tarefa, quando comparados aos blocos de linha de base e controle da aprendizagem. Os achados sugerem que a potência em alfa diminui devido o aprendizado motor quando sujeitos estão engajados na execução de uma tarefa motora complexa.

Alterações na banda alfa do eletrencefalograma durante imagética motora visual e cinestésica / Changes in the electroencephalogram alpha band during visual and kinesthetic motor imagery

Foi investigada a contribuição em potência na vizinhança do pico da banda alfa (BPA) do EEG durante imagética motora (IM). Sinais EEG (derivações occipitais e parietais) foram adquiridos em sujeitos destros (18-40 anos), durante repouso (ESP) e IM nas modalidades cinestésica (IMC) e visual (IMV), sendo 15 atletas de voleibol e 15 não-atletas. O Revised Movement Imagery Questionnaire não indicou diferenças entre grupos ou modalidades de IM; todavia os atletas imaginaram-se melhor que os não-atletas. Para ambos os grupos, a potência em BPA resultou menor em IM do que em ESP, sendo mais reduzida em IMC. Ativação cortical similar ocorreu em ambos os hemisférios de não-atletas e mais pronunciada no hemisfério esquerdo de atletas, principalmente durante IMC. Tais resultados sugerem que IM reduz a atividade de alfa de acordo com o conhecimento real da tarefa e a modalidade de IM.

This study aims at statistically assessing the differences in alpha band power, particularly in the vicinity of the alpha peak (BPA), during motor imagery (MI). Multi-channel EEG (occipital and parietal regions) was acquired at rest condition (ESP) and MI kinesthetic (MIC) and visual (MIV) modalities from right-handed male subjects (18-40 years), 15 ‘athletes’ (experienced volleyball players) and 15 ‘non-athletes’. The Revised Movement Imagery Questionnaire indicated no differences between groups or MI modalities, but athletes imagine themselves more clearly than non-athletes during MI. The power within BPA reduces in both groups, but greater in MIC than in MIV. The cortical activation was similar in both hemispheres of non-athletes but more pronounced in left hemisphere of athletes, mainly in MIC. The findings suggest that MI reduces alpha activity according to individual knowledge of real execution of motor task and MI modalities.

Changes in cortical relative power in patients submitted to a tendon transfer: a pre and post surgery study

The aim of this study is analyze possible modifications in the cerebral cortex, through quantitative electroencephalography (qEEG) in patients submitted to a tendon transfer procedure (posterior tibialis) by the Srinivasan's technique. Four subjects (2 men and 2 women), 49.25 age average (SD±21.4) were studied. All subjects have been through surgical procedure due to leprosy and had, at least, two years of drop foot condition. The qEEG measured the electrocortical activity (relative power) between 8 and 25 Hz frequencies pre and post surgery. A paired t test analyzed all data (p<0,05). The results show significant alterations in the alpha relative power, electrodes F7 (p=0.01) and F8 (p=0.021). Altogether, based on findings of the current literature, we can conclude that the tendon transfer procedure suggests electrocortical alterations sensitive to specific qEEG bands.

O objetivo deste estudo é analisar possíveis modificações no córtex cerebral, através da electrencefalografia quantitativa (EEGq), em pacientes submetidos a um procedimento de transferência de tendão (tibial posterior) pela técnica de Srinivasan. Quatro sujeitos (2 homens e 2 mulheres), com média de idade de 49,25 anos (±21,4 DP) foram estudados. Todos os sujeitos realizaram o procedimento cirúrgico devido a hanseníase e tinham, pelo menos, dois anos de pé caído. O EEGq mediu a atividade electrocortical (potencia relativa) entre freqüências de 8 e 25 Hz, no pré e pós-operatório. Um teste t pareado analisou todos os dados (p<0,05). Os resultados mostram alterações significativas na potência relativa em alfa, nos elétrodos F7 (p=0,01) e F8 (p=0,021). Baseados em recentes achados na literatura, podemos concluir que o procedimento de transferência de tendão sugere alterações eletrocorticais sensíveis às freqüên-cias específicas do EEGq.

Beta and alpha electroencephalographic activity changes after acute exercise

Exercise has been widely related to changes in cortical activation and enhanced brain functioning. Quantitative electroencephalography (qEEG) is frequently used to investigate normal and pathological conditions in the brain cortex. Therefore, the aim of the present study was to observe absolute power alterations in beta and alpha frequency bands after a maximal effort exercise. Ten healthy young volunteers were submitted to an eight-minute resting EEG (eyes closed) followed by a maximal exercise test using a mechanical cycle ergometer. Immediately after the exercise, another identical eight-minute EEG was recorded. Log transformation and paired student's t-test compared the pre and post exercise values (p<0.05). Results indicated a significant absolute power increase in beta after exercise at frontal (Fp1, F3 and F4) and central (C4) areas, which might be related to increased cortical activation.

A atividade física vem sendo relacionada com ativação cortical e melhor funcionamento do cérebro. A eletrencefalografia quantitativa (EEGq) é freqüentemente usada para investigar condições normais e patológicas do córtex cerebral. Sendo assim, o objetivo do presente estudo foi observar alterações na potência absoluta nas bandas de freqüência alfa e beta após um exercício de esforço máximo. Dez voluntários jovens e saudáveis foram submetidos a oito minutos de EEG antes e após um teste de esforço máximo em cicloergômetro. As transformações para o log e o teste t de Student foram utilizados para comparar as respostas eletrencefalográficas entre os momentos pré e pós exercício. Foi observado aumento significativo na potência absoluta de beta após o exercício nos eletrodos frontais (Fp1, F3, F4) e centrais (C4). Este resultado pode estar associado a alterações fisiológicas e ao aumento da ativação cortical.

Coerência espectral do eletrencefalograma em pacientes submetidos a transposição tendinosa: estudo pré e pós-operatório / EEG spectral coherence at patients submitted to tendon transfer surgery: study pre and post surgery

A transferência tendinosa do músculo tibial posterior é intervenção cirúrgica bastante utilizada na ortopedia para correção do pé caído por seqüela de hanseníase. Poucos modelos propuseram investigações mais significativas sobre os fenômenos plásticos cerebrais nas transferências tendinosas. O presente estudo teve como objetivo analisar a coerência espectral (CE) na Eletroencefalografia (EEG) em pacientes submetidos a transferência do tendão do tibial posterior pela técnica de Srinivasan através da EEG quantitativa (EEGq). A amostra foi composta de quatro sujeitos com pé caído devido a seqüela de hanseníase. Os parâmetros de CE do EEG foram quantificados no momento pré e pós-operatório. Os resultados mostraram que houve efeito principal para o fator momento, significativo, no par de eletrodos C3-CZ, com aumento da coerência. Entretanto, os achados da ANOVA não revelaram interação significativa entre bandas versus momento. A recuperação funcional promovida por tal cirurgia parece gerar alterações corticais.

Efeitos neuromoduladores do bromazepam quando indivíduos são expostos a uma tarefa de aprendizagem motora: eletrencefalografia quantitativa (EEGq) / Neuromodulatory effects of bromazepam when individuals were exposed to a motor learning task: quantitative electroencephalography (qEEG)

Os efeitos sedativos do bromazepam no desempenho cognitivo têm sido amplamente investigados. Várias abordagens têm sido implementadas no intuito de avaliar a influência do bromazepam em sujeitos submetidos à tarefa motora. Neste contexto, o presente estudo objetiva avaliar as alterações eletrofisiológicas em sujeitos expostos à tarefa de datilografia e tratados com bromazepam (6 mg). Os dados do EEGq foram gravados simultaneamente à tarefa. Em particular, a potência relativa na banda delta (0,5-3,5 Hz) foi analizada. O tempo de execução e erros durante a tarefa foram considerados variáveis comportamentais. O grupo experimental (bromazepam 6 mg) demonstrou melhor desempenho e valores de potência relativa mais elevados que o grupo controle (placebo). Estes resultados sugerem que menor nível de ansiedade favorece o desempenho motor.

Nonlinear dynamics characteristics in alpha rhythm of scalp electroencephalogram / 生物医学工程学杂志

In regard to the controls and schizophrenia EEGs, we have got alpha rhythm from three points of view and verified the nonlinearity of the three kinds of rhythms. The results show that neither normal EEG alpha nor patients EEG alpha have the typical nonlinear characteristics. Therefore, we could not blindly use the theories of nonlinear dynamics to analyze the rhythm of brain wave.

Estudo da coerência do eletrencefalograma na banda de frequência alfa em indivíduos adultos normais: resultados preliminares em 10 casos / EEG alpha band coherence analysis in healthy adults: preliminary results

A coerência espectral inter-hemisférica do eletrencefalograma da região occipital do escalpo (eletrodos O1 e O2) foi estimada usando a transformada rápida de Fourier. As médias de coerências na banda de freqüência alfa (alfa1 - 8,0 a 10,0 Hz e alfa2 -10,1 a 12,5 Hz) em indivíduos normais com mais de 50 anos foram comparadas com as obtidas em adultos jovens com idade inferior a 50 anos. Nossos resultados mostraram que não há diferença significativa dos níveis de coerência na banda alfa entre indivíduos em faixas etárias mais avançadas comparados aos adultos jovens.