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1.
Neuron ; 109(6): 1029-1039.e8, 2021 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-33567253

RESUMO

The theta rhythm organizes neural activity across hippocampus and entorhinal cortex. A role for theta oscillations in spatial navigation is supported by half a century of research reporting that theta frequency encodes running speed linearly so that displacement can be estimated through theta frequency integration. We show that this relationship is an artifact caused by the fact that the speed of freely moving animals could not be systematically disentangled from acceleration. Using an experimental procedure that clamps running speed at pre-set values, we find that the theta frequency of local field potentials and spike activity is linearly related to positive acceleration, but not negative acceleration or speed. The modulation by positive-only acceleration makes rhythmic activity at theta frequency unfit as a code to compute displacement or any other kinematic variable. Temporally precise variations in theta frequency may instead serve as a mechanism for speeding up entorhinal-hippocampal computations during accelerated movement.


Assuntos
Aceleração , Córtex Entorrinal/fisiologia , Hipocampo/fisiologia , Navegação Espacial/fisiologia , Ritmo Teta/fisiologia , Animais , Artefatos , Células de Grade/fisiologia , Masculino , Ratos , Ratos Long-Evans , Corrida/fisiologia
2.
Nat Commun ; 12(1): 413, 2021 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-33462202

RESUMO

Long-term potentiation (LTP) at hippocampal CA1 synapses can be expressed by an increase either in the number (N) of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors or in their single channel conductance (γ). Here, we have established how these distinct synaptic processes contribute to the expression of LTP in hippocampal slices obtained from young adult rodents. LTP induced by compressed theta burst stimulation (TBS), with a 10 s inter-episode interval, involves purely an increase in N (LTPN). In contrast, either a spaced TBS, with a 10 min inter-episode interval, or a single TBS, delivered when PKA is activated, results in LTP that is associated with a transient increase in γ (LTPγ), caused by the insertion of calcium-permeable (CP)-AMPA receptors. Activation of CaMKII is necessary and sufficient for LTPN whilst PKA is additionally required for LTPγ. Thus, two mechanistically distinct forms of LTP co-exist at these synapses.


Assuntos
Região CA1 Hipocampal/fisiologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciação de Longa Duração/fisiologia , Receptores de AMPA/metabolismo , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Masculino , Memória de Longo Prazo/fisiologia , Técnicas de Patch-Clamp , Ratos , Ritmo Teta/fisiologia
3.
Nat Commun ; 12(1): 253, 2021 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-33431847

RESUMO

Grid cells are part of a widespread network which supports navigation and spatial memory. Stable grid patterns appear late in development, in concert with extracellular matrix aggregates termed perineuronal nets (PNNs) that condense around inhibitory neurons. It has been suggested that PNNs stabilize synaptic connections and long-term memories, but their role in the grid cell network remains elusive. We show that removal of PNNs leads to lower inhibitory spiking activity, and reduces grid cells' ability to create stable representations of a novel environment. Furthermore, in animals with disrupted PNNs, exposure to a novel arena corrupted the spatiotemporal relationships within grid cell modules, and the stored representations of a familiar arena. Finally, we show that PNN removal in entorhinal cortex distorted spatial representations in downstream hippocampal neurons. Together this work suggests that PNNs provide a key stabilizing element for the grid cell network.


Assuntos
Células de Grade/citologia , Neurônios/citologia , Potenciais de Ação/fisiologia , Animais , Simulação por Computador , Córtex Entorrinal/citologia , Hipocampo/fisiologia , Masculino , Modelos Neurológicos , Ratos Long-Evans , Ritmo Teta/fisiologia , Fatores de Tempo
4.
PLoS Biol ; 18(8): e3000851, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32822389

RESUMO

High levels of the amyloid-beta (Aß) peptide have been shown to disrupt neuronal function and induce hyperexcitability, but it is unclear what effects Aß-associated hyperexcitability may have on tauopathy pathogenesis or propagation in vivo. Using a novel transgenic mouse line to model the impact of human APP (hAPP)/Aß accumulation on tauopathy in the entorhinal cortex-hippocampal (EC-HIPP) network, we demonstrate that hAPP overexpression aggravates EC-Tau aggregation and accelerates pathological tau spread into the hippocampus. In vivo recordings revealed a strong role for hAPP/Aß, but not tau, in the emergence of EC neuronal hyperactivity and impaired theta rhythmicity. Chronic chemogenetic attenuation of EC neuronal hyperactivity led to reduced hAPP/Aß accumulation and reduced pathological tau spread into downstream hippocampus. These data strongly support the hypothesis that in Alzheimer's disease (AD), Aß-associated hyperactivity accelerates the progression of pathological tau along vulnerable neuronal circuits, and demonstrates the utility of chronic, neuromodulatory approaches in ameliorating AD pathology in vivo.


Assuntos
Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Córtex Entorrinal/metabolismo , Tauopatias/genética , Proteínas tau/genética , Potenciais de Ação/fisiologia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Doença de Alzheimer/terapia , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/genética , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Dependovirus/genética , Dependovirus/metabolismo , Modelos Animais de Doenças , Eletrodos Implantados , Córtex Entorrinal/patologia , Feminino , Regulação da Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Hipocampo/metabolismo , Hipocampo/patologia , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/metabolismo , Neurônios/patologia , Agregados Proteicos , Técnicas Estereotáxicas , Tauopatias/metabolismo , Tauopatias/patologia , Tauopatias/terapia , Ritmo Teta/fisiologia , Transdução Genética , Transgenes , Proteínas tau/metabolismo
5.
Nat Commun ; 11(1): 3117, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32561726

RESUMO

On-line comprehension of natural speech requires segmenting the acoustic stream into discrete linguistic elements. This process is argued to rely on theta-gamma oscillation coupling, which can parse syllables and encode them in decipherable neural activity. Speech comprehension also strongly depends on contextual cues that help predicting speech structure and content. To explore the effects of theta-gamma coupling on bottom-up/top-down dynamics during on-line syllable identification, we designed a computational model (Precoss-predictive coding and oscillations for speech) that can recognise syllable sequences in continuous speech. The model uses predictions from internal spectro-temporal representations of syllables and theta oscillations to signal syllable onsets and duration. Syllable recognition is best when theta-gamma coupling is used to temporally align spectro-temporal predictions with the acoustic input. This neurocomputational modelling work demonstrates that the notions of predictive coding and neural oscillations can be brought together to account for on-line dynamic sensory processing.


Assuntos
Córtex Auditivo/fisiologia , Ritmo Gama/fisiologia , Modelos Neurológicos , Percepção da Fala/fisiologia , Ritmo Teta/fisiologia , Estimulação Acústica , Compreensão/fisiologia , Simulação por Computador , Sinais (Psicologia) , Humanos , Fonética
6.
Nat Neurosci ; 23(8): 992-1003, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32572235

RESUMO

Basal forebrain cholinergic neurons (BFCNs) modulate synaptic plasticity, cortical processing, brain states and oscillations. However, whether distinct types of BFCNs support different functions remains unclear. Therefore, we recorded BFCNs in vivo, to examine their behavioral functions, and in vitro, to study their intrinsic properties. We identified two distinct types of BFCNs that differ in their firing modes, synchronization properties and behavioral correlates. Bursting cholinergic neurons (Burst-BFCNs) fired synchronously, phase-locked to cortical theta activity and fired precisely timed bursts after reward and punishment. Regular-firing cholinergic neurons (Reg-BFCNs) were found predominantly in the posterior basal forebrain, displayed strong theta rhythmicity and responded with precise single spikes after behavioral outcomes. In an auditory detection task, synchronization of Burst-BFCNs to the auditory cortex predicted the timing of behavioral responses, whereas tone-evoked cortical coupling of Reg-BFCNs predicted correct detections. We propose that differential recruitment of two basal forebrain cholinergic neuron types generates behavior-specific cortical activation.


Assuntos
Prosencéfalo Basal/fisiologia , Neurônios Colinérgicos/fisiologia , Sincronização Cortical/fisiologia , Potenciais de Ação/fisiologia , Animais , Córtex Auditivo/fisiologia , Camundongos , Plasticidade Neuronal/fisiologia , Ritmo Teta/fisiologia
7.
Neuron ; 107(4): 731-744.e3, 2020 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-32526196

RESUMO

Hippocampal theta oscillations coordinate neuronal firing to support memory and spatial navigation. The medial septum (MS) is critical in theta generation by two possible mechanisms: either a unitary "pacemaker" timing signal is imposed on the hippocampal system, or it may assist in organizing target subcircuits within the phase space of theta oscillations. We used temperature manipulation of the MS to test these models. Cooling of the MS reduced both theta frequency and power and was associated with an enhanced incidence of errors in a spatial navigation task, but it did not affect spatial correlates of neurons. MS cooling decreased theta frequency oscillations of place cells and reduced distance-time compression but preserved distance-phase compression of place field sequences within the theta cycle. Thus, the septum is critical for sustaining precise theta phase coordination of cell assemblies in the hippocampal system, a mechanism needed for spatial memory.


Assuntos
Hipocampo/fisiologia , Neurônios/fisiologia , Núcleos Septais/fisiologia , Memória Espacial/fisiologia , Ritmo Teta/fisiologia , Potenciais de Ação/fisiologia , Animais , Temperatura Baixa , Masculino , Modelos Neurológicos , Células de Lugar/fisiologia , Ratos , Ratos Long-Evans
8.
J Vis Exp ; (159)2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32449716

RESUMO

Although there has been recent interest in how mindfulness meditation can affect episodic memory as well as brain structure and function, no study has examined the behavioral and neural effects of mindfulness meditation on episodic memory. Here we present a protocol that combines mindfulness meditation training, an episodic memory task, and EEG to examine how mindfulness meditation changes behavioral performance and the neural correlates of episodic memory. Subjects in a mindfulness meditation experimental group were compared to a waitlist control group. Subjects in the mindfulness meditation experimental group spent four weeks training and practicing mindfulness meditation. Mindfulness was measured before and after training using the Five Facet Mindfulness Questionnaire (FFMQ). Episodic memory was measured before and after training using a source recognition task. During the retrieval phase of the source recognition task, EEG was recorded. The results showed that mindfulness, source recognition behavioral performance, and EEG theta power in right frontal and left parietal channels increased following mindfulness meditation training. In addition, increases in mindfulness correlated with increases in theta power in right frontal channels. Therefore, results obtained from combining mindfulness meditation training, an episodic memory task, and EEG reveal the behavioral and neural effects of mindfulness meditation on episodic memory.


Assuntos
Comportamento , Eletroencefalografia , Meditação , Memória Episódica , Atenção Plena , Adulto , Encéfalo/fisiologia , Feminino , Humanos , Masculino , Inquéritos e Questionários , Ritmo Teta/fisiologia , Adulto Jovem
9.
Nat Commun ; 11(1): 2469, 2020 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-32424312

RESUMO

Based on rodent models, researchers have theorized that the hippocampus supports episodic memory and navigation via the theta oscillation, a ~4-10 Hz rhythm that coordinates brain-wide neural activity. However, recordings from humans have indicated that hippocampal theta oscillations are lower in frequency and less prevalent than in rodents, suggesting interspecies differences in theta's function. To characterize human hippocampal theta, we examine the properties of theta oscillations throughout the anterior-posterior length of the hippocampus as neurosurgical subjects performed a virtual spatial navigation task. During virtual movement, we observe hippocampal oscillations at multiple frequencies from 2 to 14 Hz. The posterior hippocampus prominently displays oscillations at ~8-Hz and the precise frequency of these oscillations correlates with the speed of movement, implicating these signals in spatial navigation. We also observe slower ~3 Hz oscillations, but these signals are more prevalent in the anterior hippocampus and their frequency does not vary with movement speed. Our results converge with recent findings to suggest an updated view of human hippocampal electrophysiology. Rather than one hippocampal theta oscillation with a single general role, high- and low-frequency theta oscillations, respectively, may reflect spatial and non-spatial cognitive processes.


Assuntos
Hipocampo/fisiologia , Ritmo Teta/fisiologia , Adulto , Eletrodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Memória Espacial/fisiologia , Análise e Desempenho de Tarefas , Adulto Jovem
10.
Nat Commun ; 11(1): 2217, 2020 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-32371879

RESUMO

Theta oscillations play a major role in temporarily defining the hippocampal rate code by translating behavioral sequences into neuronal representations. However, mechanisms constraining phase timing and cell-type-specific phase preference are unknown. Here, we employ computational models tuned with evolutionary algorithms to evaluate phase preference of individual CA1 pyramidal cells recorded in mice and rats not engaged in any particular memory task. We applied unbiased and hypothesis-free approaches to identify effects of intrinsic and synaptic factors, as well as cell morphology, in determining phase preference. We found that perisomatic inhibition delivered by complementary populations of basket cells interacts with input pathways to shape phase-locked specificity of deep and superficial pyramidal cells. Somatodendritic integration of fluctuating glutamatergic inputs defined cycle-by-cycle by unsupervised methods demonstrated that firing selection is tuneable across sublayers. Our data identify different mechanisms of phase-locking selectivity that are instrumental for flexible dynamical representations of theta sequences.


Assuntos
Região CA1 Hipocampal/fisiologia , Neurônios/fisiologia , Sinapses/fisiologia , Ritmo Teta/fisiologia , Potenciais de Ação/fisiologia , Algoritmos , Animais , Região CA1 Hipocampal/citologia , Simulação por Computador , Feminino , Cinética , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos Neurológicos , Técnicas de Patch-Clamp , Células Piramidais/fisiologia , Ratos Wistar
11.
J Neurosci ; 40(18): 3591-3603, 2020 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-32265261

RESUMO

The septo-hippocampal cholinergic system is critical for hippocampal learning and memory. However, a quantitative description of the in vivo firing patterns and physiological function of medial septal (MS) cholinergic neurons is still missing. In this study, we combined optogenetics with multichannel in vivo recording and recorded MS cholinergic neuron firings in freely behaving male mice for 5.5-72 h. We found that their firing activities were highly correlated with hippocampal theta states. MS cholinergic neurons were highly active during theta-dominant epochs, such as active exploration and rapid eye movement sleep, but almost silent during non-theta epochs, such as slow-wave sleep (SWS). Interestingly, optogenetic activation of these MS cholinergic neurons during SWS suppressed CA1 ripple oscillations. This suppression could be rescued by muscarinic M2 or M4 receptor antagonists. These results suggest the following important physiological function of MS cholinergic neurons: maintaining high hippocampal acetylcholine level by persistent firing during theta epochs, consequently suppressing ripples and allowing theta oscillations to dominate.SIGNIFICANCE STATEMENT The major source of acetylcholine in the hippocampus comes from the medial septum. Early experiments found that lesions to the MS result in the disappearance of hippocampal theta oscillation, which leads to speculation that the septo-hippocampal cholinergic projection contributing to theta oscillation. In this article, by long-term recording of MS cholinergic neurons, we found that they show a theta state-related firing pattern. However, optogenetically activating these neurons shows little effect on theta rhythm in the hippocampus. Instead, we found that activating MS cholinergic neurons during slow-wave sleep could suppress hippocampal ripple oscillations. This suppression is mediated by muscarinic M2 and M4 receptors.


Assuntos
Potenciais de Ação/fisiologia , Neurônios Colinérgicos/fisiologia , Hipocampo/fisiologia , Receptor Muscarínico M2/fisiologia , Receptor Muscarínico M4/fisiologia , Ritmo Teta/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Agonistas Colinérgicos/farmacologia , Neurônios Colinérgicos/química , Neurônios Colinérgicos/efeitos dos fármacos , Hipocampo/química , Hipocampo/efeitos dos fármacos , Masculino , Camundongos , Camundongos Transgênicos , Antagonistas Muscarínicos/farmacologia , Optogenética/métodos , Técnicas de Cultura de Órgãos , Receptor Muscarínico M2/agonistas , Receptor Muscarínico M2/antagonistas & inibidores , Receptor Muscarínico M4/agonistas , Receptor Muscarínico M4/antagonistas & inibidores , Receptores Muscarínicos/fisiologia , Ritmo Teta/efeitos dos fármacos
12.
Brain ; 143(4): 1261-1277, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-32236540

RESUMO

Frontotemporal dysconnectivity is a key pathology in schizophrenia. The specific nature of this dysconnectivity is unknown, but animal models imply dysfunctional theta phase coupling between hippocampus and medial prefrontal cortex (mPFC). We tested this hypothesis by examining neural dynamics in 18 participants with a schizophrenia diagnosis, both medicated and unmedicated; and 26 age, sex and IQ matched control subjects. All participants completed two tasks known to elicit hippocampal-prefrontal theta coupling: a spatial memory task (during magnetoencephalography) and a memory integration task. In addition, an overlapping group of 33 schizophrenia and 29 control subjects underwent PET to measure the availability of GABAARs expressing the α5 subunit (concentrated on hippocampal somatostatin interneurons). We demonstrate-in the spatial memory task, during memory recall-that theta power increases in left medial temporal lobe (mTL) are impaired in schizophrenia, as is theta phase coupling between mPFC and mTL. Importantly, the latter cannot be explained by theta power changes, head movement, antipsychotics, cannabis use, or IQ, and is not found in other frequency bands. Moreover, mPFC-mTL theta coupling correlated strongly with performance in controls, but not in subjects with schizophrenia, who were mildly impaired at the spatial memory task and no better than chance on the memory integration task. Finally, mTL regions showing reduced phase coupling in schizophrenia magnetoencephalography participants overlapped substantially with areas of diminished α5-GABAAR availability in the wider schizophrenia PET sample. These results indicate that mPFC-mTL dysconnectivity in schizophrenia is due to a loss of theta phase coupling, and imply α5-GABAARs (and the cells that express them) have a role in this process.


Assuntos
Vias Neurais/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Esquizofrenia/fisiopatologia , Lobo Temporal/fisiopatologia , Ritmo Teta/fisiologia , Adulto , Feminino , Humanos , Magnetoencefalografia , Masculino , Vias Neurais/metabolismo , Tomografia por Emissão de Pósitrons , Córtex Pré-Frontal/metabolismo , Receptores de GABA-A/metabolismo , Esquizofrenia/metabolismo , Lobo Temporal/metabolismo
13.
Sci Adv ; 6(8): eaaz2322, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32128423

RESUMO

The retrosplenial cortex is reciprocally connected with multiple structures implicated in spatial cognition, and damage to the region itself produces numerous spatial impairments. Here, we sought to characterize spatial correlates of neurons within the region during free exploration in two-dimensional environments. We report that a large percentage of retrosplenial cortex neurons have spatial receptive fields that are active when environmental boundaries are positioned at a specific orientation and distance relative to the animal itself. We demonstrate that this vector-based location signal is encoded in egocentric coordinates, is localized to the dysgranular retrosplenial subregion, is independent of self-motion, and is context invariant. Further, we identify a subpopulation of neurons with this response property that are synchronized with the hippocampal theta oscillation. Accordingly, the current work identifies a robust egocentric spatial code in retrosplenial cortex that can facilitate spatial coordinate system transformations and support the anchoring, generation, and utilization of allocentric representations.


Assuntos
Egocentrismo , Animais , Córtex Cerebral/fisiologia , Córtex Entorrinal/fisiologia , Comportamento Exploratório , Modelos Lineares , Masculino , Movimento (Física) , Córtex Motor/fisiologia , Neurônios/fisiologia , Ratos Long-Evans , Ritmo Teta/fisiologia
14.
J Neurosci ; 40(16): 3304-3317, 2020 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-32205341

RESUMO

Although the etiology of schizophrenia is still unknown, it is accepted to be a neurodevelopmental disorder that results from the interaction of genetic vulnerabilities and environmental insults. Although schizophrenia's pathophysiology is still unclear, postmortem studies point toward a dysfunction of cortical interneurons as a central element. It has been suggested that alterations in parvalbumin-positive interneurons in schizophrenia are the consequence of a deficient signaling through NMDARs. Animal studies demonstrated that early postnatal ablation of the NMDAR in corticolimbic interneurons induces neurobiochemical, physiological, behavioral, and epidemiological phenotypes related to schizophrenia. Notably, the behavioral abnormalities emerge only after animals complete their maturation during adolescence and are absent if the NMDAR is deleted during adulthood. This suggests that interneuron dysfunction must interact with development to impact on behavior. Here, we assess in vivo how an early NMDAR ablation in corticolimbic interneurons impacts on mPFC and ventral hippocampus functional connectivity before and after adolescence. In juvenile male mice, NMDAR ablation results in several pathophysiological traits, including increased cortical activity and decreased entrainment to local gamma and distal hippocampal theta rhythms. In addition, adult male KO mice showed reduced ventral hippocampus-mPFC-evoked potentials and an augmented low-frequency stimulation LTD of the pathway, suggesting that there is a functional disconnection between both structures in adult KO mice. Our results demonstrate that early genetic abnormalities in interneurons can interact with postnatal development during adolescence, triggering pathophysiological mechanisms related to schizophrenia that exceed those caused by NMDAR interneuron hypofunction alone.SIGNIFICANCE STATEMENT NMDAR hypofunction in cortical interneurons has been linked to schizophrenia pathophysiology. How a dysfunction of GABAergic cortical interneurons interacts with maturation during adolescence has not been clarified yet. Here, we demonstrate in vivo that early postnatal ablation of the NMDAR in corticolimbic interneurons results in an overactive but desynchronized PFC before adolescence. Final postnatal maturation during this stage outspreads the impact of the genetic manipulation toward a functional disconnection of the ventral hippocampal-prefrontal pathway, probably as a consequence of an exacerbated propensity toward hippocampal-evoked depotentiation plasticity. Our results demonstrate a complex interaction between genetic and developmental factors affecting cortical interneurons and PFC function.


Assuntos
Hipocampo/metabolismo , Interneurônios/metabolismo , Córtex Pré-Frontal/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Esquizofrenia/metabolismo , Animais , Modelos Animais de Doenças , Potenciais Evocados/fisiologia , Masculino , Camundongos , Camundongos Knockout , Vias Neurais/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Esquizofrenia/genética , Transdução de Sinais/fisiologia , Ritmo Teta/fisiologia
15.
Sci Rep ; 10(1): 5419, 2020 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-32214173

RESUMO

Neural activity is known to oscillate within discrete frequency bands and the synchronization between these rhythms is hypothesized to underlie information integration in the brain. Since strict synchronization is only possible for harmonic frequencies, a recent theory proposes that the interaction between different brain rhythms is facilitated by transient harmonic frequency arrangements. In this line, it has been recently shown that the transient occurrence of 2:1 harmonic cross-frequency relationships between alpha and theta rhythms (i.e. falpha ≈ 12 Hz; ftheta ≈ 6 Hz) is enhanced during effortful cognition. In this study, we tested whether achieving a state of 'mental emptiness' during meditation is accompanied by a relative decrease in the occurrence of 2:1 harmonic cross-frequency relationships between alpha and theta rhythms. Continuous EEG recordings (19 electrodes) were obtained from 43 highly experienced meditators during meditation practice, rest and an arithmetic task. We show that the occurrence of transient alpha:theta 2:1 harmonic relationships increased linearly from a meditative to an active cognitive processing state (i.e. meditation < rest < arithmetic task). It is argued that transient EEG cross-frequency arrangements that prevent alpha:theta cross-frequency coupling could facilitate the experience of 'mental emptiness' by avoiding the interaction between the memory and executive components of cognition.


Assuntos
Ritmo alfa/fisiologia , Conscientização/fisiologia , Cognição/fisiologia , Meditação/psicologia , Descanso/fisiologia , Ritmo Teta/fisiologia , Adulto , Encéfalo , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Matemática/métodos , Pessoa de Meia-Idade
16.
Medicina (B Aires) ; 80 Suppl 2: 63-66, 2020.
Artigo em Espanhol | MEDLINE | ID: mdl-32150716

RESUMO

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.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/tratamento farmacológico , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Ritmo beta/fisiologia , Estimulantes do Sistema Nervoso Central/uso terapêutico , Eletroencefalografia/métodos , Ritmo Teta/fisiologia , Adolescente , Fatores Etários , Criança , Feminino , Humanos , Masculino , Valores de Referência , Estatísticas não Paramétricas , Resultado do Tratamento
17.
Behav Neurol ; 2020: 4672340, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32089751

RESUMO

Introduction. Heretofore, research on optimizing academic performance has suffered from an inability to translate what is known about an individual's learning behaviors to how effectively they are able to use the critical nodes and hubs in their cerebral cortex for learning. A previous study from our laboratory suggests that lower theta-beta ratios (TBRs) measured by EEG may be associated with higher academic performance in a medical school curriculum. Methods: In this study, we tested the hypothesis that TBR and academic performance may be correlated with EEG coherence, a measure of brain connectivity. We analyzed the interhemispheric coherences of the subjects involved in our prior study. TBR and coherence measurements were made at 19 scalp electrode recording sites and 171 electrode combinations with eyes open and closed (EO, EC). Control data were acquired during a session of acclimation to the research protocol 3 d before an initial examination in anatomy-physiology (control exam) and were repeated five weeks later, 3 d before a second exam covering different anatomy-physiology topics (comparison exam). Results: Between the control and comparison exams, beta coherences increased significantly at the frontal pole, frontal, parietal, midtemporal, posterior temporal, and occipital recording sites under the EO condition and at the inferior frontal, central, midtemporal, and posterior temporal sites under the EC condition. Alpha coherences increased significantly at the same sites and under the same EO/EC conditions as found for the beta coherences. The beta coherences were negatively correlated with the TBR and were positively correlated with the comparison exam score at the midfrontal electrode site (F3-F4) but only under the EO condition. Beta and alpha coherences at the midfrontal, inferior frontal midtemporal, posterior temporal, and occipital sites were also negatively correlated with the average TBR under the EO condition. Conclusions: Lower TBR, an indicator of attentional control, was associated with higher alpha and beta interhemispheric coherences measured with eyes open at sites overlying the frontal, temporal, and occipital cortices. Changes in EEG coherences and TBRs might be useful as neurophysiological measures of neuroplasticity and the efficacy of strategies for preventing academic underachievement and treatments for improving academic performance.


Assuntos
Desempenho Acadêmico/tendências , Ritmo beta/fisiologia , Ritmo Teta/fisiologia , Atenção/fisiologia , Encéfalo/fisiologia , Córtex Cerebral/fisiologia , Eletroencefalografia/métodos , Lobo Frontal/fisiologia , Lateralidade Funcional/fisiologia , Humanos , Masculino , Adulto Jovem
18.
Brain Struct Funct ; 225(2): 871-879, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32060639

RESUMO

Movement-related sensory and motor activity in the brain contributes to cognitive processes. We have observed that the frequency of stepping rhythm in head-fixed mice running on a jetball overlaps with the range of frequencies that characterize hippocampal rhythmic slow activity, including theta (~ 3 to 10 Hz). On average, step-cycle troughs (i.e. when the paw touches the ground) were weakly coupled to hippocampal theta oscillations. This weak coupling was sustained during a range of running speeds. In short temporal windows, step-cycle troughs were synchronous with hippocampal theta oscillatory cycle troughs, while during other periods they led or lagged behind theta cycles. Furthermore, simultaneously recorded theta rhythmic medial septal neurons in the basal forebrain were phase-coupled to both step-cycles and theta-cycles. We propose that the weak overall phase relationship of step-cycles with theta-cycles signifies a distinct mode of information processing. Transient synchronization of the step-cycle with theta may indicate the engagement of septo-hippocampal-entorhinal network with the current heading of the animal.


Assuntos
Hipocampo/fisiologia , Locomoção , Neurônios/fisiologia , Núcleos Septais/fisiologia , Ritmo Teta/fisiologia , Animais , Masculino , Camundongos Endogâmicos C57BL , Vias Neurais/fisiologia , Processamento de Sinais Assistido por Computador
19.
Psychon Bull Rev ; 27(3): 563-570, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32052268

RESUMO

Human behavior fluctuates. A growing body of evidence has demonstrated that behavioral performance in perception fluctuates rhythmically, with dynamics closely resembling spectral features of neural oscillations. However, it is unclear whether the behavioral fluctuations in a complex cooperation context can also express similar rhythmic features, and, more importantly, whether these behavioral rhythms are synchronized among co-actors in a neurophysiologically relevant manner. To answer these questions, we applied a time-resolved approach, previously used for probing individual-level behavioral oscillations in perception, in a complex social interaction context, and further probed dyad-level behavioral synchrony. Twenty pairs of male participants completed, in dyad, joint-action tasks with cooperation or competition demand. We extracted behavioral rhythms from ongoing cooperative performance and measured behavioral synchrony by computing the phase coherence of these behavioral rhythms between dyad members. Despite the absence of significant behavioral oscillations in individuals' amplitude spectrum, we observed enhanced theta-band phase coherence between co-actors' behavioral rhythms during cooperation compared to competition conditions. These results indicate that cooperative behaviors of co-actors fluctuated synchronously within the theta band, providing a behavioral counterpart of theta-band interbrain synchrony in cooperation reported in previous hyperscanning studies. Furthermore, the observed behavioral synchrony could be used as a sensitive predictor of cooperation pattern, as evidenced by its significant correlation with leader-follower relationship during cooperation.


Assuntos
Córtex Cerebral/fisiologia , Comportamento Competitivo , Comportamento Cooperativo , Sincronização Cortical/fisiologia , Relações Interpessoais , Ritmo Teta/fisiologia , Adulto , Humanos , Masculino , Adulto Jovem
20.
J Neurosci ; 40(11): 2343-2356, 2020 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-32019830

RESUMO

Goal-directed behavior can benefit from proactive adjustments of cognitive control that occur in anticipation of forthcoming cognitive control demands (CCD). Predictions of forthcoming CCD are thought to depend on learning and memory in two ways: First, through direct experience, associative encoding may link previously experienced CCD to its triggering item, such that subsequent encounters with the item serve to cue retrieval of (i.e., predict) the associated CCD. Second, in the absence of direct experience, pattern completion and mnemonic integration mechanisms may allow CCD to be generalized from its associated item to other items related in memory. While extant behavioral evidence documents both types of CCD prediction, the neurocognitive mechanisms giving rise to these predictions remain largely unexplored. Here, we tested two hypotheses: (1) memory-guided predictions about CCD precede control adjustments due to the actual CCD required; and (2) generalization of CCD can be accomplished through integration mechanisms that link partially overlapping CCD-item and item-item associations in memory. Supporting these hypotheses, the temporal dynamics of theta and alpha power in human electroencephalography data (n = 43, 26 females) revealed that an associative CCD effect emerges earlier than interaction effects involving actual CCD. Furthermore, generalization of CCD from one item (X) to another item (Y) was predicted by a decrease in alpha power following the presentation of the X-Y pair. These findings advance understanding of the mechanisms underlying memory-guided adjustments of cognitive control.SIGNIFICANCE STATEMENT Cognitive control adaptively regulates information processing to align with task goals. Experience-based expectations enable adjustments of control, leading to improved performance when expectations match the actual control demand required. Using EEG, we demonstrate that memory for past cognitive control demand proactively guides the allocation of cognitive control, preceding adjustments of control triggered by the demands of the present environment. Furthermore, we demonstrate that learned cognitive control demands can be generalized through mnemonic integration processes, enabling the spread of expectations about cognitive control demands to items associated in memory. We reveal that this generalization is linked to decreased alpha oscillation in medial frontal channels. Collectively, these findings provide new insights into how memory-control interactions facilitate goal-directed behavior.


Assuntos
Aprendizagem por Associação/fisiologia , Cognição/fisiologia , Memória/fisiologia , Adaptação Psicológica , Adolescente , Adulto , Ritmo alfa/fisiologia , Mapeamento Encefálico , Sinais (Psicologia) , Eletroencefalografia , Feminino , Objetivos , Humanos , Masculino , Desempenho Psicomotor/fisiologia , Tempo de Reação , Teste de Stroop , Ritmo Teta/fisiologia , Fatores de Tempo , Adulto Jovem
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