Research on electroencephalogram power spectral density of stroke patients under transcranial direct current stimulation / 生物医学工程学杂志

Transcranial direct current stimulation (tDCS) has become a new method of post-stroke rehabilitation treatment and is gradually accepted by people. However, the neurophysiological mechanism of tDCS in the treatment of stroke still needs further study. In this study, we recruited 30 stroke patients with damage to the left side of the brain and randomly divided them into a real tDCS group (15 cases) and a sham tDCS group (15 cases). The resting EEG signals of the two groups of subjects before and after stimulation were collected, then the difference of power spectral density was analyzed and compared in the band of delta, theta, alpha and beta, and the delta/alpha power ratio (DAR) was calculated. The results showed that after real tDCS, delta band energy decreased significantly in the left temporal lobes, and the difference was statistically significant ( P < 0.05); alpha band energy enhanced significantly in the occipital lobes, and the difference was statistically significant ( P < 0.05); the difference of theta and beta band energy was not statistically significant in the whole brain region ( P > 0.05). Furthermore, the difference of delta, theta, alpha and beta band energy was not statistically significant after sham tDCS ( P > 0.05). On the other hand, the DAR value of stroke patients decreased significantly after real tDCS, and the difference was statistically significant ( P < 0.05), and there was no significant difference in sham tDCS ( P > 0.05). This study reveals to a certain extent the neurophysiological mechanism of tDCS in the treatment of stroke.

Association between clinical condition and F-waves changes in the acute phase of stroke / Associação entre condição clínica e alterações das ondas-F na fase aguda do acidente vascular cerebral

ABSTRACT Objective To relate F-waves with clinical and laboratory exams in the acute phase of stroke. Methods Inclusion criteria for this cross-sectional study were: hemiplegia, absence of previous cranial trauma, myopathy, diabetes, alcoholism or other known causes of peripheral neuropathy, and normal sensory and motor conduction. The National Institutes of Health Stroke Scale (NIHSS) score, glycemia, glucosilate hemoglobin, and CPK were obtained at admission by routine blood exams. After hospital admission, the F-wave latencies and persistence were obtained from the deep peroneal nerve using symmetrical techniques. Results Evaluation of 20 individuals – mean age 66 years, 50% male and 85% Caucasian – showed association of F-wave persistence with glycemia (r = 0.71; p < 0.001) and NIHSS categorized (NIHSS 1-7 = 65.0 x NIHSS 9-23 = 100; p = 0.004). Multivariate analysis found only association of F-wave persistence with glycemia β = 0.59 (0.44–0.74); p < 0.001. Conclusion The increase in the persistence of F-waves are associated with hyperglycemia in the acute phase of stroke.

RESUMO Objetivo Relacionar as ondas-F com exames clínicos e laboratoriais na fase aguda do acidente vascular cerebral (AVC). Os critérios de inclusão para este estudo transversal foram: hemiplegia, ausência de trauma craniano, miopatia, diabetes, alcoolismo ou outra causa conhecida de neuropatia periférica, além de condução sensorial e motora normal. O National Institutes of Health Stroke Scale (NIHSS), glicemia, hemoglobina glicada e CPK foram obtidos na admissão por meio de exames de rotina. Após a admissão hospitalar, a latência e persistência das ondas-F foram obtidas por meio da estimulação do nervo fibular profundo utilizando técnicas simétricas. Foram avaliados 20 indivíduos – média de idade 66 anos, 50% homem e 85% caucasianos – apresentaram associação univariada da persistência das ondas-F com glicemia (r = 0.71; p < 0.001) e NIHSS categorizado (NIHSS 1–7 = 65.0 x NIHSS 9-23 = 100; p = 0.004). Na regressão multivariada foi encontrado associação somente entre persistência de ondas-F com glicemia β = 0.59(0.44–0.74); p < 0.001. Conclusão O aumento da persistência de ondas-F está associado com maior nível de glicemia na fase aguda do AVC.

Bases fisiológicas do eletroencefalograma / Electroencephalogram physiological basis

O principal objetivo deste artigo é descrever as origens fisiológicas do eletroencefalograma (EEG). Para entender isso, é necessário conhecer algumas questões: os geradores neurais e a base celular da atividade elétrica, as interações neuronais e a condutividade dos tecidos através dos quais os potenciais de campo transitarão até serem captados por eletrodos, e a orientação relativa dos geradores com os eletrodos. Assim, são estudados os mecanismos fundamentais dos potenciais de campo extracelulares e a soma da atividade elétrica das populações de neurônios captada fora do sistema nervoso central (SNC) que origina o EEG. Este registra a diferença de voltagem entre locais do cérebro ao longo do tempo.

The main objective of this paper is to describe the physiological origins of the electroencephalogram (EEG). To understand this, it is necessary to know some issues: neural generators and the cellular basis of electrical activity, neuronal interactions and the conductivity of the tissues through which the potentials will travel until they are captured by the electrodes, and the relative orientation of the generators to the electrodes. Therefore, the fundamental mechanisms of extracellular potentials and the sum of the electrical activity of populations of neurons captured outside the central nervous system (CNS) that originate the EEG were studied. The latter records the voltage difference between locations of the brain over time.

Neural Substrates of Hanja (Logogram) and Hangul (Phonogram) Character Readings by Functional Magnetic Resonance Imaging

The two basic scripts of the Korean writing system, Hanja (the logography of the traditional Korean character) and Hangul (the more newer Korean alphabet), have been used together since the 14th century. While Hanja character has its own morphemic base, Hangul being purely phonemic without morphemic base. These two, therefore, have substantially different outcomes as a language as well as different neural responses. Based on these linguistic differences between Hanja and Hangul, we have launched two studies; first was to find differences in cortical activation when it is stimulated by Hanja and Hangul reading to support the much discussed dual-route hypothesis of logographic and phonological routes in the brain by fMRI (Experiment 1). The second objective was to evaluate how Hanja and Hangul affect comprehension, therefore, recognition memory, specifically the effects of semantic transparency and morphemic clarity on memory consolidation and then related cortical activations, using functional magnetic resonance imaging (fMRI) (Experiment 2). The first fMRI experiment indicated relatively large areas of the brain are activated by Hanja reading compared to Hangul reading. The second experiment, the recognition memory study, revealed two findings, that is there is only a small difference in recognition memory for semantic transparency, while for the morphemic clarity was much larger between Hanja and Hangul. That is the morphemic clarity has significantly more effect than semantic transparency on recognition memory when studies by fMRI in correlation with behavioral study.

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. .

Non-epileptiform EEG abnormalities: an overview / Anormalidades eletrencefalográficas não epileptiformes: uma visão geral

More than 80 years after its introduction by Hans Berger, the electroencephalogram (EEG) remains as an important supplementary examination in the investigation of neurological disorders and gives valuable and accurate information about cerebral function. Abnormal EEG findings may include ictal patterns, interictal epileptiform activity and non-epileptiform abnormalities. The aim of this study is to make an overview on the main non-epileptiform EEG abnormalities, emphasizing the pathologic findings and the importance of their recognition, excluding periodic patterns and EEG physiologic changes. Scientific articles were selected from MEDLINE and PubMed database. The presence of non-epileptiform EEG abnormalities provide evidence of brain dysfunction that are not specific to a particular etiology and may be related to a number of disorders affecting the brain. Although these abnormalities are not specific, they can direct attention to the diagnostic possibilities and guide the best treatment choice.

Mais de 80 anos após sua introdução por Hans Berger, o eletrencefalograma (EEG) permanece como importante exame complementar na investigação de transtornos neurológicas e fornece informações valiosas e precisas a respeito da função cerebral. Achados eletrencefalográficos anormais podem incluir padrões ictais, atividade epileptiforme interictal e anormalidades eletrencefalográficas não epileptiformes. O objetivo deste estudo é fazer uma revisão das principais anormalidades eletrencefalográficas não epileptiformes, enfatizando os achados patológicos e a importância de seu reconhecimento, excluindo padrões periódicos e alterações eletrencefalográficas fisiológicas. Foram selecionados artigos científicos por meio de pesquisa nas bases de dados MEDLINE e PubMed. A presença de anormalidades eletrencefalográficas não epileptiformes fornece evidências de disfunção cerebral, as quais não são específicas para uma etiologia particular e podem estar relacionadas a uma série de desordens que afetam o encéfalo. Embora essas anormalidades não sejam específicas, elas podem direcionar a atenção para as possibilidades diagnósticas e guiar a escolha do melhor tratamento.