ABSTRACT
The prefrontal cortex and hippocampus may support sequential working memory beyond episodic memory and spatial navigation. This stereoelectroencephalography (SEEG) study investigated how the dorsolateral prefrontal cortex (DLPFC) interacts with the hippocampus in the online processing of sequential information. Twenty patients with epilepsy (eight women, age 27.6 ± 8.2 years) completed a line ordering task with SEEG recordings over the DLPFC and the hippocampus. Participants showed longer thinking times and more recall errors when asked to arrange random lines clockwise (random trials) than to maintain ordered lines (ordered trials) before recalling the orientation of a particular line. First, the ordering-related increase in thinking time and recall error was associated with a transient theta power increase in the hippocampus and a sustained theta power increase in the DLPFC (3-10 Hz). In particular, the hippocampal theta power increase correlated with the memory precision of line orientation. Second, theta phase coherences between the DLPFC and hippocampus were enhanced for ordering, especially for more precisely memorized lines. Third, the theta band DLPFC → hippocampus influence was selectively enhanced for ordering, especially for more precisely memorized lines. This study suggests that theta oscillations may support DLPFC-hippocampal interactions in the online processing of sequential information.
Subject(s)
Adult , Female , Humans , Young Adult , Male , Epilepsy , Hippocampus , Memory, Short-Term , Mental Recall , Prefrontal Cortex , Theta RhythmABSTRACT
The hippocampus has been extensively implicated in spatial navigation in rodents and more recently in bats. Numerous studies have revealed that various kinds of spatial information are encoded across hippocampal regions. In contrast, investigations of spatial behavioral correlates in the primate hippocampus are scarce and have been mostly limited to head-restrained subjects during virtual navigation. However, recent advances made in freely-moving primates suggest marked differences in spatial representations from rodents, albeit some similarities. Here, we review empirical studies examining the neural correlates of spatial navigation in the primate (including human) hippocampus at the levels of local field potentials and single units. The lower frequency theta oscillations are often intermittent. Single neuron responses are highly mixed and task-dependent. We also discuss neuronal selectivity in the eye and head coordinates. Finally, we propose that future studies should focus on investigating both intrinsic and extrinsic population activity and examining spatial coding properties in large-scale hippocampal-neocortical networks across tasks.
Subject(s)
Animals , Humans , Spatial Navigation/physiology , Hippocampus/physiology , Primates , Neurons/physiology , Theta Rhythm/physiologyABSTRACT
Transcranial magneto-acoustic-electrical stimulation is a new non-invasive neuromodulation technology, in which the induced electric field generated by the coupling effect of ultrasound and static magnetic field are used to regulate the neural rhythm oscillation activity in the corresponding brain region. The purpose of this paper is to investigate the effects of transcranial magneto-acoustic-electrical stimulation on the information transfer and communication in neuronal clusters during memory. In the experiment, twenty healthy adult Wistar rats were randomly divided into a control group (five rats) and stimulation groups (fifteen rats). Transcranial magneto-acoustic-electrical stimulation of 0.05~0.15 T and 2.66~13.33 W/cm 2 was applied to the rats in stimulation groups, and no stimulation was applied to the rats in the control group. The local field potentials signals in the prefrontal cortex of rats during the T-maze working memory tasks were acquired. Then the coupling differences between delta rhythm phase, theta rhythm phase and gamma rhythm amplitude of rats in different parameter stimulation groups and control group were compared. The experimental results showed that the coupling intensity of delta and gamma rhythm in stimulation groups was significantly lower than that in the control group ( P<0.05), while the coupling intensity of theta and gamma rhythm was significantly higher than that in the control group ( P<0.05). With the increase of stimulation parameters, the degree of coupling between delta and gamma rhythm showed a decreasing trend, while the degree of coupling between theta and gamma rhythm tended to increase. The preliminary results of this paper indicated that transcranial magneto-acoustic-electrical stimulation inhibited delta rhythmic neuronal activity and enhanced the oscillation of theta and gamma rhythm in the prefrontal cortex, thus promoted the exchange and transmission of information between neuronal clusters in different spatial scales. This lays the foundation for further exploring the mechanism of transcranial magneto-acoustic-electrical stimulation in regulating brain memory function.
Subject(s)
Animals , Rats , Acoustics , Electric Stimulation , Memory, Short-Term/physiology , Rats, Wistar , Theta Rhythm/physiology , Transcranial Direct Current StimulationABSTRACT
The present study was aimed to explore the correlation between θ-γ neural oscillations phase-amplitude coupling (PAC) in hippocampal CA3 area and the changes of spatial identifying and cognitive ability before and after shock avoidance training in rats. According to the results of Y-type maze shock avoidance training, the rats were divided into two groups: the fast avoidance response group and the general avoidance response group. The local field potential (LFP) of hippocampal CA3 area was recorded by wireless telemetry before and after shock avoidance training. The variation of θ oscillation (3-7 Hz) and low-γ neural oscillation (30-60 Hz) PAC in hippocampal CA3 area was analyzed by MATLAB wavelet packet extraction technique. The results showed that, compared with the general avoidance response group, the fast avoidance response group exhibited higher θ-γ neural oscillation PAC in hippocampal CA3 area before training. θ-γ oscillation PAC in hippocampal CA3 area was increased in both groups after training. It was also noticed that θ-γ neural oscillation PAC of some frequency bands in the general avoidance response group were significantly higher than those in the fast avoidance response group. The results suggest that certain intensity of training can change the spatial identifying and cognitive ability of rats, and the mechanism may involve the increase of the synchrony of θ-γ neural oscillation, i.e., the enhancement of θ-γ phase-amplitude alternating frequency coupling in hippocampal neurons.
Subject(s)
Animals , Rats , Cognition , Hippocampus , Neurons , Theta RhythmABSTRACT
El cociente Theta-Beta (T/B) del electroencefalograma cuantificado (EEGQ) de los pacientes con trastorno por déficit de atención e hiperactividad (TDAH) constituye una variable del EEG característica del trastorno primario con una precisión global del 89%. El objetivo de este estudio es medir el cociente T/B de una población de con TDAH y los efectos del tratamiento farmacológico con psicoestimulantes y no psicoestimulantes sobre el cociente T/B. La muestra estaba formada por 85 sujetos de entre 6 y los 18 años (68 niños y 17 niñas) con el diagnóstico de TDAH de subtipo inatento y combinado, según los criterios del DSM-V. Se les realizó un EEGQ con medición del cociente T/B antes y después de 6 meses de tratamiento con fármacos psicoestimulantes y no psicoestimulantes. Se compararon ambos grupos mediante la prueba de rangos con signo de Wilcoxon para muestras relacionadas. En el 86% de los casos el cociente T/B fue elevado respecto de los valores normales para la edad. La reducción en el cociente T/B fue significativa en el grupo tratado con psicoestimulantes aunque la reducción con los no psicoestimulantes no fue significativa. En conclusión, se confirma la elevación del cociente T/B en los pacientes con TDAH. Los fármacos psicoestimulantes disminuyen de forma significativa el cociente T/B elevado en los pacientes con TDAH tras 6 meses de tratamiento.
Theta-Beta (T / B) ratio of the quantified electroencephalogram (EEGQ) in patients with attention deficit hyperactivity disorder (ADHD) constitutes a characteristic EEG variable of the primary disorder with an overall accuracy of 89%. The objective of this study was to measure the T/B ratio in a sample of patients with ADHD and the effects of the treatment with psychostimulants and non-psychostimulants on the T/B ratio. The sample consisted of 85 children between 6 and 18 years (68 males and 17 females) with the diagnosis of the inattentive and combined subtype of ADHD, according to the criteria of the DSM-V. An EEGQ was performed with measurement of the T/B ratio before and after 6 months of treatment with psychostimulant and non-psychostimulant drugs. Both groups were compared using the Wilcoxon signed range test for related samples. The results showed that 86% of the cases had a T/B ratio above the normal values for the age of them. The reduction in the T/B ratio was statistically significant in the group of patients treated with psychostimulants. The reduction of non-psychostimulants was not significant. In conclusion, we confirmed the high T/B ratio in patients with ADHD. Psychostimulant drugs decrease the elevated T/B ratio in patients with ADHD after 6 months of treatment.
Subject(s)
Humans , Male , Female , Child , Adolescent , Attention Deficit Disorder with Hyperactivity/physiopathology , Attention Deficit Disorder with Hyperactivity/drug therapy , Theta Rhythm/physiology , Beta Rhythm/physiology , Electroencephalography/methods , Central Nervous System Stimulants/therapeutic use , Reference Values , Age Factors , Treatment Outcome , Statistics, NonparametricABSTRACT
Objective: Theta-burst stimulation (TBS) modulates synaptic plasticity more efficiently than standard repetitive transcranial magnetic stimulation delivery and may be a promising modality for neuropsychiatric disorders such as autism spectrum disorder (ASD). At present there are few effective interventions for prefrontal cortex dysfunction in ASD. We report on an open-label, pilot study of intermittent TBS (iTBS) to target executive function deficits and restricted, repetitive behaviors in male children and adolescents with ASD. Methods: Ten right-handed, male participants, aged 9-17 years with ASD were enrolled in an open-label trial of iTBS treatment. Fifteen sessions of neuronavigated iTBS at 100% motor threshold targeting the right dorsolateral prefrontal cortex were delivered over 3 weeks. Results: Parent report scores on the Repetitive Behavior Scale Revised and the Yale-Brown Obsessive Compulsive Scale demonstrated improvements with iTBS treatment. Participants demonstrated improvements in perseverative errors on the Wisconsin Card Sorting Test and total time for the Stroop test. The iTBS treatments were well tolerated with no serious adverse effects. Conclusion: These preliminary results suggest that further controlled interventional studies of iTBS for ASD are warranted.
Subject(s)
Humans , Male , Child , Adolescent , Theta Rhythm/physiology , Transcranial Magnetic Stimulation/methods , Autism Spectrum Disorder/therapy , Pilot Projects , Treatment Outcome , Prefrontal Cortex/physiopathology , Signal Detection, Psychological , Aftercare , Autism Spectrum Disorder/physiopathology , Autism Spectrum Disorder/psychology , Obsessive Behavior/psychology , Obsessive-Compulsive Disorder/psychologyABSTRACT
Stimulation of the medial forebrain bundle (MFB) can reinforce intracranial self-stimulation (ICSS) in rodents (i.e., reward-seeking behavior). The MFB stimulation produces a highly reliable behavioral output that enabled a clear distinction of the animal behavioral states between the non-ICSS and ICSS periods. However, the cortical states during these reward-seeking behaviors are not fully characterized in comparison to those during volitional behavior. This study was designed to characterize the cortical rhythms of and coherence between prefrontal cortex and hippocampus during the wheel-turning behavior reinforced by the ICSS in comparison to the wheel-turning without ICSS. We used a wheel for freely moving mice, which was programmed to deliver cathode currents through an electrode in the MFB at each one-quarter turn of the wheel to induce ICSS. The wheel-turning epochs were extracted from the pre-ICSS, ICSS and post-ICSS sessions and the prefrontal EEGs and the hippocampal LFPs in the epochs were analyzed with power and synchronization analyses. During the ICSS, the EEG power decreased at 6~10 Hz in the prefrontal cortex, while was not significantly altered in the hippocampus. Furthermore, we found that the phase synchrony between the prefrontal cortex and the hippocampus corresponding to information transmission between the two regions during reward-seeking motion decreased preceding MFB stimulation reinforced by ICSS. Our findings suggest that theta-activity can be reliably dissociated from active behavior if the animal is involved in self-stimulation.
Subject(s)
Animals , Mice , Behavior, Animal , Electrodes , Electroencephalography , Hippocampus , Medial Forebrain Bundle , Prefrontal Cortex , Rodentia , Theta RhythmABSTRACT
Epileptic spike is an indicator of hyper-excitability and hyper-synchrony in the neural networks. The inhibitory effects of spikes on theta rhythms (4-8 Hz) might be helpful to understand the mechanism of epileptic damage on the cognitive functions. To quantitatively evaluate the inhibitory effects of spikes on theta rhythms, intracerebral electroencephalogram (EEG) recordings with both sporadic spikes (SSs) and spike-free transient period between adjacent spikes were selected in 4 patients in the status of rapid eyes movement (REM) sleep with temporal lobe epilepsy (TLE) under the pre-surgical monitoring. The electrodes of hippocampal CA3 and entorhinal cortex (EC) were employed, since CA3 and EC built up one of key loops to investigate cognition and epilepsy. These SSs occurred only in CA3, only in EC, or in both CA3 and EC synchronously. Theta power was respectively estimated around SSs and during the spike-free transient period by Gabor wavelet transform and Hilbert transform. The intermittent extent was then estimated to represent for the loss of theta rhythms during the spike-free transient period. The following findings were obtained: (1) The prominent rhythms were in theta frequency band; (2) The spikes could transiently reduce theta power, and the inhibitory effect was severer around SSs in both CA3 and EC synchronously than that around either SSs only in EC or SSs only in CA3; (3) During the spike-free transient period, theta rhythms were interrupted with the intermittent theta rhythms left and theta power level continued dropping, implying the inhibitory effect was sustained. Additionally, the intermittent extent of theta rhythms was converged to the inhibitory extent around SSs; (4) The average theta power level during the spike-free transient period might not be in line with the inhibitory extent of theta rhythms around SSs. It was concluded that the SSs had negative effects on theta rhythms transiently and directly, the inhibitory effects aroused by SSs sustained during the spike-free transient period and were directly related to the intermittent extent. It was indicated that the loss of theta rhythms might qualify exactly the sustained inhibitory effects on theta rhythms aroused by spikes in EEG. The work provided an argumentation about the relationship between the transient negative impact of interictal spike and the loss of theta rhythms during spike-free activity for the first time, offered an intuitive methodology to estimate the inhibitory effect of spikes by EEG, and might be helpful to the analysis of EEG rhythms based on local field potentials (LFPs) in deep brain.
Subject(s)
Humans , Male , CA3 Region, Hippocampal , Electroencephalography , Entorhinal Cortex , Epilepsy, Temporal Lobe , Theta RhythmABSTRACT
The dysfunction of subthalamic nucleus is the main cause of Parkinson's disease. Local field potentials in human subthalamic nucleus contain rich physiological information. The present study aimed to quantify the oscillatory and dynamic characteristics of local field potentials of subthalamic nucleus, and their modulation by the medication therapy for Parkinson's disease. The subthalamic nucleus local field potentials were recorded from patients with Parkinson's disease at the states of on and off medication. The oscillatory features were characterised with the power spectral analysis. Furthermore, the dynamic features were characterised with time-frequency analysis and the coefficient of variation measure of the time-variant power at each frequency. There was a dominant peak at low beta-band with medication off. The medication significantly suppressed the low beta component and increased the theta component. The amplitude fluctuation of neural oscillations was measured by the coefficient of variation. The coefficient of variation in 4-7 Hz and 60-66 Hz was increased by medication. These effects proved that medication had significant modulation to subthalamic nucleus neural oscillatory synchronization and dynamic features. The subthalamic nucleus neural activities tend towards stable state under medication. The findings would provide quantitative biomarkers for studying the mechanisms of Parkinson's disease and clinical treatments of medication or deep brain stimulation.
Subject(s)
Humans , Antiparkinson Agents , Therapeutic Uses , Beta Rhythm , Electrodes , Evoked Potentials , Oscillometry , Parkinson Disease , Drug Therapy , Subthalamic Nucleus , Theta RhythmABSTRACT
The purpose of the present study is to explore the relationship of spatial learning ability and specific electrical activities of neural oscillations in the rat. The fast and general avoidance response groups were selected on the basis of the animals' responses to the electric shock in Y type maze, and their local field potentials (LFPs) of hippocampal CA3 area were recorded by wireless telemetry before and after shock avoidance training, respectively. The components of neural oscillations related to spatial identifying and learning ability were analyzed. The results showed that, compared with the general avoidance response group, the fast avoidance response group did not show any differences of LFPs in hippocampal CA3 area before electric shock avoidance trial, but showed significantly increased percentages of 0-10 Hz and 30-40 Hz rhythm in right hippocampal CA3 area after the shock avoidance training (P < 0.01 or P < 0.05). Fast Fourier transform showed that percentage increase of 0-10 Hz band occurred mainly in θ (3-7 Hz) frequency, and 30-40 Hz frequency change was equivalent to the γ1 band. Furthermore, compared with those before training, only the percentages of β, β2 (20-30 Hz) and γ1 rhythm increased (P < 0.01 or P < 0.05) in fast avoidance response rats after training, while the θ rhythm percentage remained unchanged. In contrast, θ rhythm percentage and the large amplitude (intensity: +2.5 - -2.5 db) θ waves in right CA3 area of general avoidance response rats were significantly reduced after training (P < 0.01). These results suggest that the increased percentages of β2 and γ1 rhythm and high-level (unchanged) percentage of θ rhythm in the right hippocampus CA3 area might be related to strong spatial cognition ability of fast avoidance response rats.
Subject(s)
Animals , Rats , Avoidance Learning , Beta Rhythm , CA3 Region, Hippocampal , Physiology , Electroshock , Gamma Rhythm , Spatial Learning , Theta RhythmABSTRACT
Acute and long-term effects of mindfulness meditation on theta-band activity are not clear. The aim of this study was to investigate frontal theta differences between long- and short-term mindfulness practitioners before, during, and after mindfulness meditation. Twenty participants were recruited, of which 10 were experienced Buddhist meditators. Despite an acute increase in the theta activity during meditation in both the groups, the meditators showed lower trait frontal theta activity. Therefore, we suggested that this finding is a neural correlate of the expert practitioners’ ability to limit the processing of unnecessary information (e.g., discursive thought) and increase the awareness of the essential content of the present experience. In conclusion, acute changes in the theta band throughout meditation did not appear to be a specific correlate of mindfulness but were rather related to the concentration properties of the meditation. Notwithstanding, lower frontal theta activity appeared to be a trait of mindfulness practices.
Os efeitos agudos e de longo prazo da meditação mindfulness sobre a atividade da banda teta não são claros. O objetivo deste estudo foi investigar as diferenças da banda teta na região frontal entre praticantes de mindfulness iniciantes e experientes. Desta forma, vinte participantes foram recrutados (dez meditadores budistas experientes e dez não-meditadores). Apesar do aumento agudo da atividade teta durante a meditação para ambos os grupos, os meditadores apresentaram uma menor potência em ambas as condições. Sugerimos que este achado é um correlato neural da capacidade dos praticantes especialistas em limitar o processamento de informações desnecessárias e aumentar a conscientização sobre o conteúdo essencial da experiência presente. Em conclusão, as alterações agudas na banda teta durante a meditação devem estar relacionadas ao processo de concentração típico de qualquer técnica meditativa. No entanto, a atividade teta reduzida encontrada entre meditadores experientes de mindfulness parece ser uma característica desta prática específica.
Subject(s)
Adult , Humans , Middle Aged , Frontal Lobe/physiology , Meditation , Mindfulness , Theta Rhythm/physiology , Attention/physiology , Electroencephalography , Practice, Psychological , Time FactorsABSTRACT
Epilepsy clinically has an inhibitory impact on cognitive function, but whether it is associated with epileptogenesis is unclear. Since the epileptic spike characterizes temporal lobe epilepsy (TLE), the present study was aimed to analyze the transient effects of sporadic spikes (SSs) on theta rhythm during epileptogenesis. The local field potentials (LFPs) were recorded in CA1 area in four rats with the pilocarpine injections during exploration, and theta phase stability and power were globally estimated around SSs, also during prolonged period without SS (both as experiments) as well as pre-injections (control). Finally, the LFPs were simulated by changing the average excitatory and inhibitory synaptic gain values (including slow and fast inhibition loops) with the help of simplified dynamical model of CA1 networks, and then theta phase stability was evaluated in several cases. It was found that the SSs could have negative impacts on theta rhythm both transiently and persistently, which may be dependent on the temporal courses leading to epilepsy, being acuter in early stage than later stage, but even in latent stage, theta power was strong. The simulations partly demonstrated that the synaptic imbalance concomitant with the occurrence of SSs might be related to the dynamics of theta phase stability. The results indicate that the SSs might have persistent negative impacts on the cognition rhythm, and the effects might alter during epileptogenesis, leading to the cognitive dysfunction.
Subject(s)
Animals , Rats , CA1 Region, Hippocampal , Epilepsy, Temporal Lobe , Pilocarpine , Theta RhythmABSTRACT
Hippocampal neuronal network oscillation is closely related to the memory, anxiety and behavioral inhibition of mammalian. The cognitive decline and behavioral disinhibition in the patients with Alzheimer's disease (AD) may be relevant to amyloid β protein (Aβ)-induced impairment in hippocampal neuronal cooperative activity. However, it is not well known whether intrahippocampal injection of Aβ could induce behavioral disinhibition and neuronal network disorder, as well as cognition decline in animals. In the present study, we observed the effects of intracerebral injection of Aβ(1-42) on the spatial memory and behavioral inhibition of rats by using Morris water maze and elevated plus-maze tests. Further, we analyzed hippocampal theta rhythm by recording hippocampal local field potential. The results showed that: (1) bilateral hippocampal injection of Aβ(1-42) reduced the anxious behavior of rats, with a significant behavioral disinhibition in the elevated plus-maze test, representing as an increase in the mean entering times and mean residence time in the open arm; (2) Aβ(1-42) injection resulted in a significant impairment of spatial memory in rats, with significantly increased mean escape latencies in hidden platform test; (3) Aβ(1-42) disrupted the induction of theta rhythm induced by tail pinch, with a significant reduction in the peak power, not the peak power frequency of the theta rhythm. These experimental results indicate that intrahippocampal injection of Aβ(1-42) can induce behavioral disinhibition and theta rhythm suppression, as well as spatial memory impairment in rats, which suggests that the cognition deficits and behavior impairments in AD are probably associated with the Aβ-induced disruption of hippocampal theta rhythm and consequent down-regulation of synaptic plasticity.
Subject(s)
Animals , Rats , Amyloid beta-Peptides , Down-Regulation , Hippocampus , Maze Learning , Neuronal Plasticity , Peptide Fragments , Spatial Memory , Theta RhythmABSTRACT
The striatum, the largest component of the basal ganglia, is usually subdivided into associative, motor and limbic components. However, the electrophysiological interactions between these three subsystems during behavior remain largely unknown. We hypothesized that the striatum might be particularly active during exploratory behavior, which is presumably associated with increased attention. We investigated the modulation of local field potentials (LFPs) in the striatum during attentive wakefulness in freely moving rats. To this end, we implanted microelectrodes into different parts of the striatum of Wistar rats, as well as into the motor, associative and limbic cortices. We then used electromyograms to identify motor activity and analyzed the instantaneous frequency, power spectra and partial directed coherence during exploratory behavior. We observed fine modulation in the theta frequency range of striatal LFPs in 92.5 ± 2.5% of all epochs of exploratory behavior. Concomitantly, the theta power spectrum increased in all striatal channels (P < 0.001), and coherence analysis revealed strong connectivity (coefficients >0.7) between the primary motor cortex and the rostral part of the caudatoputamen nucleus, as well as among all striatal channels (P < 0.001). Conclusively, we observed a pattern of strong theta band activation in the entire striatum during attentive wakefulness, as well as a strong coherence between the motor cortex and the entire striatum. We suggest that this activation reflects the integration of motor, cognitive and limbic systems during attentive wakefulness.
Subject(s)
Animals , Female , Male , Rats , Behavior, Animal/physiology , Corpus Striatum/physiology , Evoked Potentials/physiology , Exploratory Behavior/physiology , Theta Rhythm/physiology , Wakefulness/physiology , Electrodes, Implanted , Microelectrodes , Rats, WistarABSTRACT
As a rhythmic neural activity, neural oscillation exists all over the nervous system, in structures as diverse as the cerebral cortex, hippocampus, subcortical nuclei and sense organs. This review firstly presents some evidence that synchronous neural oscillations in theta and gamma bands reveal much about the origin and nature of cognitive processes such as learning and memory. And then it introduces the novel analyzing algorithms of neural oscillations, which is a directionality index of neural information flow (NIF) as a measure of synaptic plasticity. An example of application used such an analyzing algorithms of neural oscillations has been provided.
Subject(s)
Animals , Humans , Biological Clocks , Brain , Physiology , Cognition , Physiology , Learning , Physiology , Memory , Physiology , Nervous System Physiological Phenomena , Physiology , Neural Pathways , Physiology , Neuronal Plasticity , Physiology , Synapses , Physiology , Theta Rhythm , PhysiologyABSTRACT
O estabelecimento das memórias de longo prazo requer uma efetiva comunicação do hipocampo com o neocortex. Um mecanismo plausível envolvido na comunicação neuronal e na plasticidade sináptica é a sincronização da atividade elétrica cerebral na frequência teta. Estudos recentes mostraram que a sincronização entre os ritmos teta do hipocampo e do córtex pré-frontal aumenta durante a evocação das memórias aversivas e diminui após a extinção do aprendizado. Entretanto, outros ritmos cerebrais, como as ondas delta, também estão envolvidos nas respostas comportamentais do medo e nos processos de memória. Desta forma, o ritmo teta, que já foi bastante estudado pelo seu papel no aprendizado e na memória, e o ritmo delta, por seu envolvimento no ciclo sono-vigília, foram investigados considerando a relação causal entre eles. Ainda não está bem estabelecido como os ritmos delta e teta podem juntos contribuir nos processos cognitivos ou como os ritmos do hipocampo podem influenciar ou receber influencias da atividade cortical. Neste trabalho foi investigada a contribuição dos ritmos delta e teta em função do estado comportamental (vigília ativa ou congelamento) e do tipo de memória evocada (recente ou remota). Além disso, foi realizada uma análise de sincronia de fase para inferir a dinâmica da atividade elétrica entre o córtex pré-frontal medial, o hipocampo e o córtex visual durante a evocação das memórias de medo. Para tanto, os animais foram treinados e testados numa tarefa de condicionamento de medo ao contexto. Neste tipo de condicionamento, o animal aprende a estabelecer uma associação entre um determinado contexto (caixa de condicionamento) e um evento aversivo (choque elétrico nas patas) que ocorreu neste contexto...
The establishment of long-term memories requires effective communication of the hippocampus to the neocortex. Electrophysiological activities between hippocampus and prefrontal cortex have shown higher theta synchronization during retrieval of aversive memories and lower during extinction learning. While theta activity is more differently related to learning and memory, delta waves have been more discussed in the context of sleep or "offline" states. Few studies have investigated delta waves during "on-line" states (such as task-relevant situations) and the contribution of these rhythms to memory storage remains unclear. We recorded electrophysiological data to study the contributions of delta and theta waves in cortico-hippocampal system of rats underwent to contextual fear conditioning. Our experiment consisted of environmental pre-exposition, training with electrical footshocks, and recent/remote memory tests. Two groups of rats were tested one or eighteen days post training for recent or remote memory, respectively. Local field potential time series of two behavioral states were sampled: active exploration and freezing. The results showed that theta and delta rhythms play an important role in behavioral responses and memory processing. They are related to fear recall and their contribution depend on the recent or remote memory. Additionally, using an order parameter we show that theta contribution is strongly pronounced in active exploration, decreasing during freezing. In the latter, the rats presented pronounced delta waves in freezing. Moreover, a behavioral-dependent causality measure showed an increase of theta influence in delta rhythms, resulting in a theta slowing in aversive memory retrieval. Finally, we show an increased synchrony between hippocampus and prefrontal cortex during recall of recent memory, but a decreased synchrony in remote memory...
Subject(s)
Animals , Rats , Conditioning, Classical , Electrophysiology , Hippocampus , Learning , Memory, Short-Term , Memory/physiology , Prefrontal Cortex , Rats , Theta RhythmSubject(s)
Humans , Female , Temporal Lobe , Echoencephalography , Epilepsy, Temporal Lobe , Theta RhythmABSTRACT
This study was conducted to analyze the impact on human's left and right brain by mental calculation based on principal components analysis (PCA). Electroencephalogram (EEG) data were collected from twenty-one people before and during mental calculation. In each subject, we first calculated the PCA load of maximum principal component of the theta wave in four brain electrodes of the forehead, then we analyzed the relationship between mental calculating event and each brain electrode. From closing eye to relaxing event and to performing mental calculation event, it was shown that the weight of left head decreased and the weight of right head increased. These results indicate that mental calculation increases the workload on the right forehead, and on the right side of head obviously.