RESUMO
Abnormal patterns of brain connectivity characterize epilepsy. However, little is known about these patterns during the stages preceding a seizure induced by pentylenetetrazol (PTZ). To investigate brain connectivity in male Wistar rats during the preictal phase of PTZ-induced seizures (60 mg/kg), we recorded local field potentials in the primary motor (M1) cortex, the ventral anterior (VA) nucleus of the thalamus, the hippocampal CA1 area, and the dentate gyrus (DG) during the baseline period and after PTZ administration. While there were no changes in power density between the baseline and preictal periods, we observed an increase in directional functional connectivity in theta from the hippocampal formation to M1 and VA, as well as in middle gamma from DG to CA1 and from CA1 to M1, and also in slow gamma from M1 to CA1. These findings are supported by increased phase coherence between DG-M1 in theta and CA1-M1 in middle gamma, as well as enhanced phase-amplitude coupling of delta-middle gamma in M1 and delta-fast gamma in CA1. Interestingly, we also noted a slight decrease in phase synchrony between CA1 and VA in slow gamma. Together, these results demonstrate increased functional connectivity between brain regions during the PTZ-induced preictal period, with this increase being particularly driven by the hippocampal formation.
Assuntos
Encéfalo , Pentilenotetrazol , Ratos Wistar , Convulsões , Animais , Pentilenotetrazol/farmacologia , Masculino , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Ratos , Vias Neurais/fisiopatologia , Vias Neurais/efeitos dos fármacos , Modelos Animais de Doenças , Eletroencefalografia/métodos , Região CA1 Hipocampal/efeitos dos fármacos , Região CA1 Hipocampal/fisiopatologia , Convulsivantes/toxicidade , Convulsivantes/farmacologia , Ondas Encefálicas/efeitos dos fármacos , Ondas Encefálicas/fisiologia , Córtex Motor/efeitos dos fármacos , Córtex Motor/fisiopatologiaRESUMO
More than 100 years of research have passed by and still the human electroencephalogram (EEG) remains a puzzle to be solved. Starting from his studies on plethysmography until his theories on brain thermodynamics, Hans Berger was able to refine his method of recording cortical signs with the apparatus at his disposal in an ordinary neuropsychiatric yard towards an early account of human EEG. This review is an appraisal of his contribution to the field of modern neurophysiology.
Mais de 100 anos se passaram e o eletroencefalograma humano (EEG) continua sendo um enigma a ser desvendado. A partir de seus estudos sobre pletismografia até suas teorias sobre termodinâmica cerebral, Hans Berger conseguiu refinar seu método de registro da atividade elétrica cortical com os equipamentos a sua disposição em uma ala psiquiátrica comum produzindo uma descrição acurada do EEG humano. Esta revisão é um breve resumo de sua contribuição para o campo da neurofisiologia moderna.
Assuntos
Ondas Encefálicas , Temperatura Alta , Humanos , Eletroencefalografia , Encéfalo/fisiologia , NeurofisiologiaRESUMO
Decision-making is a process that allows adapting behavior in response to feedback to achieve a goal. Previous studies have suggested that the cerebral cortex shows different activation patterns in response to feedback. However, the effects of reward and punishment on learning contexts and decision-making are not clear. Thus, this experiment compared the effects of reward and punishment on behavior and the electroencephalographic activity of cortical areas related to decision-making in a no-risk context. Twenty healthy males were asked to perform a decision-making task under two conditions in which the goal was to finish in the shortest time possible. In the reward condition, the more points the participant accumulated the sooner the task ended, while in the punishment condition, the more points accumulated the longer the task lasted. Lower reaction times were found in the reward condition, characterized by a higher absolute power of the slow bands in almost all the cortices recorded. Changes in the interhemispheric correlation were also obtained in the comparison of the two feedback conditions. Results suggest that changes in the type of feedback affect cortical functionality and behavioral execution during decision-making, with the reward being related to a quick emotional response strategy and punishment associated with slower and, likely, more reasoned responses.
Assuntos
Ondas Encefálicas/fisiologia , Córtex Cerebral/fisiologia , Tomada de Decisões/fisiologia , Eletroencefalografia , Retroalimentação Psicológica/fisiologia , Desempenho Psicomotor/fisiologia , Punição , Recompensa , Adolescente , Adulto , Humanos , Masculino , Adulto JovemRESUMO
Spectral power density (SPD) indexed by electroencephalogram (EEG) recordings has recently gained attention in elucidating neural mechanisms of chronic pain syndromes and medication use. We compared SPD variations between 15 fibromyalgia (FM) women in use of opioid in the last three months (73.33% used tramadol) with 32 non-users. EEG data were obtained with Eyes Open (EO) and Eyes Closed (EC) resting state. SPD peak amplitudes between EO-EC were smaller in opioid users in central theta, central beta, and parietal beta, and at parietal delta. However, these variations were positive for opioid users. Multivariate analyses of variance (ANOVAs) revealed that EO-EC variations in parietal delta were negatively correlated with the disability due to pain, and central and parietal beta activity variations were positively correlated with worse sleep quality. These clinical variables explained from 12.5 to 17.2% of SPD variance. In addition, central beta showed 67% sensitivity / 72% specificity and parietal beta showed 73% sensitivity/62% specificity in discriminating opioid users from non-users. These findings suggest oscillations in EEG might be a sensitive surrogate marker to screen FM opioid users and a promising tool to understand the effects of opioid use and how these effects relate to functional and sleep-related symptoms.
Assuntos
Analgésicos Opioides/uso terapêutico , Mapeamento Encefálico , Ondas Encefálicas/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Eletroencefalografia , Fibromialgia/tratamento farmacológico , Descanso , Adulto , Encéfalo/fisiopatologia , Estudos Transversais , Feminino , Fibromialgia/diagnóstico , Fibromialgia/fisiopatologia , Humanos , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Processamento de Sinais Assistido por Computador , Fatores de TempoRESUMO
Altered Excitatory/Inhibitory (E/I) balance of cortical synaptic inputs has been proposed as a central pathophysiological factor for psychiatric neurodevelopmental disorders, including schizophrenia (SZ). However, direct measurement of E/I synaptic balance have not been assessed in vivo for any validated SZ animal model. Using a mouse model useful for the study of SZ we show that a selective ablation of NMDA receptors (NMDAr) in cortical and hippocampal interneurons during early postnatal development results in an E/I imbalance in vivo, with synaptic inputs to pyramidal neurons shifted towards excitation in the adult mutant medial prefrontal cortex (mPFC). Remarkably, this imbalance depends on the cortical state, only emerging when theta and gamma oscillations are predominant in the network. Additional brain slice recordings and subsequent 3D morphological reconstruction showed that E/I imbalance emerges after adolescence concomitantly with significant dendritic retraction and dendritic spine re-localization in pyramidal neurons. Therefore, early postnatal ablation of NMDAr in cortical and hippocampal interneurons developmentally impacts on E/I imbalance in vivo in an activity-dependent manner.
Assuntos
Ondas Encefálicas/fisiologia , Fenômenos Eletrofisiológicos/fisiologia , Hipocampo/fisiopatologia , Interneurônios/fisiologia , Rede Nervosa/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Células Piramidais/fisiologia , Receptores de N-Metil-D-Aspartato/deficiência , Esquizofrenia/fisiopatologia , Fatores Etários , Animais , Modelos Animais de Doenças , Hipocampo/metabolismo , Interneurônios/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Rede Nervosa/metabolismo , Parvalbuminas/metabolismo , Córtex Pré-Frontal/metabolismo , Células Piramidais/metabolismo , Esquizofrenia/metabolismoRESUMO
For more than a decade, neurofeedback interventions have been applied with the goal of improving cognitive functions in older adults. Some of these studies have been reviewed, but only in combination with experiments conducted in young adults or with studies seeking to modify functions not related to cognition. The purpose of the present review is to assess whether neurofeedback interventions benefit cognition in elderly adults. We included all neurofeedback studies conducted in older adults, whether healthy or affected by a clinical condition, that attempted to ameliorate any domain of cognition, with no restrictions by publication date. Fourteen studies were eligible for this review. Neurofeedback improved memory in healthy and unhealthy participants mainly when the theta and sensorimotor rhythm (SMR) frequencies were trained. In addition, other cognitive domains benefited from this intervention. Conversely, neurofeedback had no effect on attention processes. Although different studies used markedly different methods, almost all of them reported positive effects of neurofeedback in at least one cognitive domain. New interventions under consideration should be tested using placebo-controlled, double-blind experimental designs with follow-up evaluations.
Assuntos
Envelhecimento/fisiologia , Disfunção Cognitiva , Memória/fisiologia , Neurorretroalimentação/fisiologia , Idoso , Ondas Encefálicas/fisiologia , HumanosRESUMO
Detection of unexpected, yet relevant events is essential in daily life. fMRI studies have revealed the involvement of the ventral attention network (VAN), including the temporo-parietal junction (TPJ), in such process. In this MEG study with 34 participants (17 women), we used a bimodal (visual/auditory) attention task to determine the neuronal dynamics associated with suppression of the activity of the VAN during top-down attention and its recruitment when information from the unattended sensory modality is involuntarily integrated. We observed an anticipatory power increase of alpha/beta oscillations (12-20 Hz, previously associated with functional inhibition) in the VAN following a cue indicating the modality to attend. Stronger VAN power increases were associated with better task performance, suggesting that the VAN suppression prevents shifting attention to distractors. Moreover, the TPJ was synchronized with the frontal eye field in that frequency band, indicating that the dorsal attention network (DAN) might participate in such suppression. Furthermore, we found a 12-20 Hz power decrease and enhanced synchronization, in both the VAN and DAN, when information between sensory modalities was congruent, suggesting an involvement of these networks when attention is involuntarily enhanced due to multisensory integration. Our results show that effective multimodal attentional allocation includes the modulation of the VAN and DAN through upper-alpha/beta oscillations. Altogether these results indicate that the suppressing role of alpha/beta oscillations might operate beyond sensory regions.
Assuntos
Atenção/fisiologia , Mapeamento Encefálico , Ondas Encefálicas/fisiologia , Córtex Cerebral/fisiologia , Magnetoencefalografia , Rede Nervosa/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Percepção da Fala/fisiologia , Adulto , Feminino , Humanos , Masculino , Adulto JovemRESUMO
Recent evidence indicates that soluble amyloid-ß (Aß) species induce imbalances in excitatory and inhibitory transmission, resulting in neural network functional impairment and cognitive deficits during early stages of Alzheimer's disease (AD). To evaluate the in vivo effects of two soluble Aß species (Aß 25-35 and Aß 1-40) on commissural CA3-to-CA1 (cCA3-to-CA1) synaptic transmission and plasticity, and CA1 oscillatory activity, we used acute intrahippocampal microinjections in adult anaesthetized male Wistar rats. Soluble Aß microinjection increased cCA3-to-CA1 synaptic variability without significant changes in synaptic efficiency. High-frequency CA3 stimulation was rendered inefficient by soluble Aß intrahippocampal injection to induce long-term potentiation and to enhance synaptic variability in CA1, contrasting with what was observed in vehicle-injected subjects. Although soluble Aß microinjection significantly increased the relative power of γ-band and ripple oscillations and significantly shifted the average vector of θ-to-γ phase-amplitude coupling (PAC) in CA1, it prevented θ-to-γ PAC shift induced by high-frequency CA3 stimulation, opposite to what was observed in vehicle-injected animals. These results provide further evidence that soluble Aß species induce synaptic dysfunction causing abnormal synaptic variability, impaired long-term plasticity, and deviant oscillatory activity, leading to network activity derailment in the hippocampus.
Assuntos
Peptídeos beta-Amiloides/farmacologia , Ondas Encefálicas/efeitos dos fármacos , Região CA1 Hipocampal/diagnóstico por imagem , Região CA3 Hipocampal/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Sinapses/efeitos dos fármacos , Animais , Estimulação Elétrica , Masculino , Vias Neurais/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Ratos , Ratos Wistar , Transmissão Sináptica/efeitos dos fármacosRESUMO
Modulation of brain activity is one of the main mechanisms capable of demonstrating the synchronization dynamics of neural oscillations. In epilepsy, modulation is a key concept since seizures essentially result from neural hypersynchronization and hyperexcitability. In this study, we have introduced a time-dependent index based on the Kullback-Leibler divergence to quantify the effects of phase and frequency modulations of neural oscillations in neonatal mice exhibiting epileptiform activity induced by Zika virus (ZIKV) infection. Through this index, we demonstrate that fast oscillations (gamma and beta 2) are the more susceptible modulated rhythms in terms of phase, during seizures, whereas slow waves (delta and theta) mainly undergo changes in frequency. The index also allowed detection of specific patterns associated with the interdependent modulation of phase and frequency in neural activity. Furthermore, by comparing ZIKV modulations with the general computational model Epileptors, we verify different signatures related to the brain rhythms modulation in phase and frequency. These findings instigate new studies on the effects of ZIKV infection on neuronal networks from electrophysiological activities, and how different mechanisms can trigger epilepsy.
Assuntos
Ondas Encefálicas/fisiologia , Epilepsia/fisiopatologia , Neurônios/fisiologia , Infecção por Zika virus/virologia , Animais , Ritmo beta/fisiologia , Encéfalo/patologia , Encéfalo/virologia , Modelos Animais de Doenças , Epilepsia/complicações , Epilepsia/virologia , Ritmo Gama/fisiologia , Humanos , Camundongos , Neurônios/virologia , Zika virus/patogenicidade , Infecção por Zika virus/complicações , Infecção por Zika virus/fisiopatologiaRESUMO
Insights on the neurocognitive particularities of expert individuals have benefited from language studies on professional simultaneous interpreters (PSIs). Accruing research indicates that behavioral advantages in this population are restricted to those skills that are directly taxed during professional practice (e.g., translation as opposed to reading), but little is known about the neural signatures of such selective effects. To illuminate the issue, we recruited 17 PSIs and 15 non-interpreter bilinguals and compared behavioral and electrophysiological markers of word reading and translation from and into their native and non-native languages (L1 and L2, respectively). PSIs exhibited greater delta-theta (1-8 âHz) power across all tasks over varying topographies, but these were accompanied by faster performance only in the case of translation conditions. Moreover, neural differences in PSIs were most marked for L2-L1 translation (the dominant interpreting direction in their market), which exhibited maximally widespread modulations that selectively correlated with behavioral outcomes. Taken together, our results suggest that interpreting experience involves distinct neural signatures across reading and translation mechanisms, but that these are systematically related with processing efficiency only in domains that face elevated demands during everyday practice (i.e., L2-L1 translation). These findings can inform models of simultaneous interpreting, in particular, and expert cognitive processing, in general.