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1.
Int J Mol Sci ; 22(5)2021 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-33806419

RESUMO

Arterial smooth muscle exhibits rhythmic oscillatory contractions called vasomotion and believed to be a protective mechanism against tissue hypoperfusion or hypoxia. Oscillations of vascular tone depend on voltage and follow oscillations of the membrane potential. Voltage-gated sodium channels (Nav), responsible for the initiation and propagation of action potentials in excitable cells, have also been evidenced both in animal and human vascular smooth muscle cells (SMCs). For example, they contribute to arterial contraction in rats, but their physiopathological relevance has not been established in human vessels. In the present study, we investigated the functional role of Nav in the human artery. Experiments were performed on human uterine arteries obtained after hysterectomy and on SMCs dissociated from these arteries. In SMCs, we recorded a tetrodotoxin (TTX)-sensitive and fast inactivating voltage-dependent INa current. Various Nav genes, encoding α-subunit isoforms sensitive (Nav 1.2; 1.3; 1.7) and resistant (Nav 1.5) to TTX, were detected both in arterial tissue and in SMCs. Nav channels immunostaining showed uniform distribution in SMCs and endothelial cells. On arterial tissue, we recorded variations of isometric tension, ex vivo, in response to various agonists and antagonists. In arterial rings placed under hypoxic conditions, the depolarizing agent KCl and veratridine, a specific Nav channels agonist, both induced a sustained contraction overlaid with rhythmic oscillations of tension. After suppression of sympathetic control either by blocking the release of catecholamine or by antagonizing the target adrenergic response, rhythmic activity persisted while the sustained contraction was abolished. This rhythmic activity of the arteries was suppressed by TTX but, in contrast, only attenuated by antagonists of calcium channels, Na+/Ca2+ exchanger, Na+/K+-ATPase and the cardiac Nav channel. These results highlight the role of Nav as a novel key element in the vasomotion of human arteries. Hypoxia promotes activation of Nav channels involved in the initiation of rhythmic oscillatory contractile activity.


Assuntos
Artérias/metabolismo , Hipóxia/metabolismo , Contração Muscular/fisiologia , Canais de Sódio Disparados por Voltagem/metabolismo , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Adulto , Animais , Artérias/efeitos dos fármacos , Canais de Cálcio/metabolismo , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Feminino , Humanos , Pessoa de Meia-Idade , Contração Muscular/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Miócitos de Músculo Liso/efeitos dos fármacos , Miócitos de Músculo Liso/metabolismo , Trocador de Sódio e Cálcio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Tetrodotoxina/farmacologia
2.
Nat Commun ; 12(1): 1900, 2021 03 26.
Artigo em Inglês | MEDLINE | ID: mdl-33772000

RESUMO

The computations performed by a neural circuit depend on how it integrates its input signals into an output of its own. In the retina, ganglion cells integrate visual information over time, space, and chromatic channels. Unlike the former two, chromatic integration is largely unexplored. Analogous to classical studies of spatial integration, we here study chromatic integration in mouse retina by identifying chromatic stimuli for which activation from the green or UV color channel is maximally balanced by deactivation through the other color channel. This reveals nonlinear chromatic integration in subsets of On, Off, and On-Off ganglion cells. Unlike the latter two, nonlinear On cells display response suppression rather than activation under balanced chromatic stimulation. Furthermore, nonlinear chromatic integration occurs independently of nonlinear spatial integration, depends on contributions from the rod pathway and on surround inhibition, and may provide information about chromatic boundaries, such as the skyline in natural scenes.


Assuntos
Potenciais de Ação/fisiologia , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Campos Visuais/fisiologia , Vias Visuais/fisiologia , Potenciais de Ação/efeitos dos fármacos , Algoritmos , Animais , Cor , Feminino , HEPES/farmacologia , Masculino , Camundongos Endogâmicos C57BL , Dinâmica não Linear , Estimulação Luminosa/métodos , Piridazinas/farmacologia , Retina/citologia , Estricnina/farmacologia
3.
Nat Neurosci ; 24(3): 401-411, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33619404

RESUMO

Pyramidal cells and GABAergic interneurons fire together in balanced cortical networks. In contrast to this general rule, we describe a distinct neuron type in mice and rats whose spiking activity is anti-correlated with all principal cells and interneurons in all brain states but, most prevalently, during the down state of non-REM (NREM) sleep. We identify these down state-active (DSA) neurons as deep-layer neocortical neurogliaform cells that express ID2 and Nkx2.1 and are weakly immunoreactive to neuronal nitric oxide synthase. DSA neurons are weakly excited by deep-layer pyramidal cells and strongly inhibited by several other GABAergic cell types. Spiking of DSA neurons modified the sequential firing order of other neurons at down-up transitions. Optogenetic activation of ID2+Nkx2.1+ interneurons in the posterior parietal cortex during NREM sleep, but not during waking, interfered with consolidation of cue discrimination memory. Despite their sparsity, DSA neurons perform critical physiological functions.


Assuntos
Potenciais de Ação/fisiologia , Proteína 2 Inibidora de Diferenciação/metabolismo , Interneurônios/fisiologia , Lobo Parietal/fisiologia , Células Piramidais/fisiologia , Sono/fisiologia , Fator Nuclear 1 de Tireoide/metabolismo , Animais , Interneurônios/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Vias Neurais/fisiologia , Óxido Nítrico Sintase Tipo I/metabolismo , Optogenética , Lobo Parietal/metabolismo
4.
Nat Commun ; 12(1): 1027, 2021 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-33589639

RESUMO

Sleep spindles facilitate memory consolidation in the cortex during mammalian non-rapid eye movement sleep. In rodents, phase-locked firing during spindles may facilitate spike-timing-dependent plasticity by grouping pre-then-post-synaptic cell firing within ~25 ms. Currently, microphysiological evidence in humans for conditions conducive for spike-timing-dependent plasticity during spindles is absent. Here, we analyze field potentials and unit firing from middle/upper layers during spindles from 10 × 10 microelectrode arrays at 400 µm pitch in humans. We report strong tonic and phase-locked increases in firing and co-firing within 25 ms during spindles, especially those co-occurring with down-to-upstate transitions. Co-firing, spindle co-occurrence, and spindle coherence are greatest within ~2 mm, and high co-firing of units on different contacts depends on high spindle coherence between those contacts. Spindles propagate at ~0.28 m/s in distinct patterns, with correlated cell co-firing sequences. Spindles hence organize spatiotemporal patterns of neuronal co-firing in ways that may provide pre-conditions for plasticity during non-rapid eye movement sleep.


Assuntos
Potenciais de Ação/fisiologia , Córtex Cerebral/fisiologia , Consolidação da Memória/fisiologia , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Sono REM/fisiologia , Adulto , Córtex Cerebral/anatomia & histologia , Eletrodos Implantados , Eletroencefalografia , Epilepsia/patologia , Epilepsia/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neurônios/citologia , Técnicas Estereotáxicas
5.
Nat Commun ; 12(1): 1103, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33597516

RESUMO

Neurons in some sensory areas reflect the content of working memory (WM) in their spiking activity. However, this spiking activity is seldom related to behavioral performance. We studied the responses of inferotemporal (IT) neurons, which exhibit object-selective activity, along with Frontal Eye Field (FEF) neurons, which exhibit spatially selective activity, during the delay period of an object WM task. Unlike the spiking activity and local field potentials (LFPs) within these areas, which were poor predictors of behavioral performance, the phase-locking of IT spikes and LFPs with the beta band of FEF LFPs robustly predicted successful WM maintenance. In addition, IT neurons exhibited greater object-selective persistent activity when their spikes were locked to the phase of FEF LFPs. These results reveal that the coordination between prefrontal and temporal cortex predicts the successful maintenance of visual information during WM.


Assuntos
Macaca mulatta/fisiologia , Memória de Curto Prazo/fisiologia , Neurônios/fisiologia , Córtex Pré-Frontal/fisiologia , Lobo Temporal/fisiologia , Potenciais de Ação/fisiologia , Algoritmos , Animais , Lobo Frontal/citologia , Lobo Frontal/fisiologia , Masculino , Modelos Neurológicos , Estimulação Luminosa , Córtex Pré-Frontal/citologia , Lobo Temporal/citologia
6.
Nat Neurosci ; 24(3): 326-330, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33603228

RESUMO

By investigating the topology of neuronal co-activity, we found that mnemonic information spans multiple operational axes in the mouse hippocampus network. High-activity principal cells form the core of each memory along a first axis, segregating spatial contexts and novelty. Low-activity cells join co-activity motifs across behavioral events and enable their crosstalk along two other axes. This reveals an organizational principle for continuous integration and interaction of hippocampal memories.


Assuntos
Condicionamento Operante/fisiologia , Hipocampo/fisiologia , Memória/fisiologia , Rede Nervosa/fisiologia , Neurônios/fisiologia , Sacarose/administração & dosagem , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Condicionamento Operante/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Memória/efeitos dos fármacos , Camundongos , Rede Nervosa/efeitos dos fármacos , Neurônios/efeitos dos fármacos
7.
Nature ; 592(7852): 86-92, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33473216

RESUMO

The anatomy of the mammalian visual system, from the retina to the neocortex, is organized hierarchically1. However, direct observation of cellular-level functional interactions across this hierarchy is lacking due to the challenge of simultaneously recording activity across numerous regions. Here we describe a large, open dataset-part of the Allen Brain Observatory2-that surveys spiking from tens of thousands of units in six cortical and two thalamic regions in the brains of mice responding to a battery of visual stimuli. Using cross-correlation analysis, we reveal that the organization of inter-area functional connectivity during visual stimulation mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas3. We find that four classical hierarchical measures-response latency, receptive-field size, phase-locking to drifting gratings and response decay timescale-are all correlated with the hierarchy. Moreover, recordings obtained during a visual task reveal that the correlation between neural activity and behavioural choice also increases along the hierarchy. Our study provides a foundation for understanding coding and signal propagation across hierarchically organized cortical and thalamic visual areas.


Assuntos
Potenciais de Ação/fisiologia , Córtex Visual/anatomia & histologia , Córtex Visual/fisiologia , Animais , Conjuntos de Dados como Assunto , Eletrofisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Estimulação Luminosa , Tálamo/anatomia & histologia , Tálamo/citologia , Tálamo/fisiologia , Córtex Visual/citologia
8.
Nat Commun ; 12(1): 100, 2021 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-33397954

RESUMO

Hippocampal synaptic plasticity includes both long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength, and has been implicated in shaping place field representations that form upon initial exposure to a novel environment. However, direct evidence causally linking either LTP or LTD to place fields remains limited. Here, we show that hippocampal LTD regulates the acute formation and maintenance of place fields using electrophysiology and blocking specifically LTD in freely-moving rats. We also show that exploration of a novel environment produces a widespread and pathway specific de novo synaptic depression in the dorsal hippocampus. Furthermore, disruption of this pathway-specific synaptic depression alters both the dynamics of place field formation and the stability of the newly formed place fields, affecting spatial memory in rats. These results suggest that activity-dependent synaptic depression is required for the acquisition and maintenance of novel spatial information.


Assuntos
Região CA1 Hipocampal/fisiologia , Depressão Sináptica de Longo Prazo/fisiologia , Potenciais de Ação/fisiologia , Animais , Aprendizagem da Esquiva , Endocitose , Potenciais Pós-Sinápticos Excitadores/fisiologia , Comportamento Exploratório , Peptídeos/metabolismo , Ratos Sprague-Dawley , Receptores de AMPA/metabolismo
9.
Muscle Nerve ; 63(4): 472-476, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33399235

RESUMO

BACKGROUND: Precise placement of stimulating and recording electrodes is vital when performing nerve conduction studies (NCSs). In this study, we aimed to determine whether ultrasonography (US) was more precise in localizing the superficial radial nerve (SRN), dorsal ulnar cutaneous nerve (DUCN), ulnar nerve (UN) crossing the cubital tunnel, and radial nerve (RN) crossing the spiral groove (SG) compared to conventional techniques. METHODS: Thirty healthy young subjects (15 male) were recruited. Each subject underwent both landmark-based and US-guided NCS. Onset latencies and amplitudes of compound motor action potentials (CMAPs) and sensory nerve action potentials (SNAPs), and stimulation levels (ie, intensity × duration) required to obtain maximal CMAP amplitudes were compared between the two techniques. RESULTS: The mean CMAP amplitudes of the UN above the cubital tunnel (9.55 ± 1.96 vs 8.96 ± 1.94 mV, P = .030), UN below the cubital tunnel (10.11 ± 2.07 vs 9.37 ± 1.95 mV, P < .001), and RN below the SG (5.21 ± 1.56 vs 4.34 ± 1.03 mV, P < .001) were significantly greater using US-guided NCSs compared to landmark-based NCSs. The mean onset latency of the DUCN was significantly shorter using US-guided NCSs (1.49 ± 0.15 vs 1.57 ± 0.14 ms, P = .020). The required stimulation level in the UN and RN was significantly lower using US-guided NCSs. CONCLUSIONS: When performing NCSs, US guidance provides a more precise localization of the stimulator and electrodes for the DUCN, UN, and RN, while providing comparable localization for the SRN, compared to landmark-based techniques.


Assuntos
Síndrome do Túnel Carpal/diagnóstico por imagem , Exame Neurológico , Nervo Ulnar/diagnóstico por imagem , Ultrassonografia , Potenciais de Ação/fisiologia , Adulto , Eletrodiagnóstico/métodos , Feminino , Guias como Assunto , Humanos , Masculino , Condução Nervosa/fisiologia , Exame Neurológico/métodos , Exame Neurológico/normas , Ultrassonografia/métodos , Ultrassonografia/normas
10.
Neural Netw ; 135: 192-200, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33401225

RESUMO

We analyse mathematically the constraints on weights resulting from Hebbian and STDP learning rules applied to a spiking neuron with weight normalisation. In the case of pure Hebbian learning, we find that the normalised weights equal the promotion probabilities of weights up to correction terms that depend on the learning rate and are usually small. A similar relation can be derived for STDP algorithms, where the normalised weight values reflect a difference between the promotion and demotion probabilities of the weight. These relations are practically useful in that they allow checking for convergence of Hebbian and STDP algorithms. Another application is novelty detection. We demonstrate this using the MNIST dataset.


Assuntos
Potenciais de Ação/fisiologia , Aprendizado Profundo , Modelos Neurológicos , Plasticidade Neuronal/fisiologia , Algoritmos , Humanos , Neurônios/fisiologia
11.
Nat Neurosci ; 24(3): 379-390, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33495635

RESUMO

The nucleus accumbens shell (NAcSh) and the ventral pallidum (VP) are critical for reward processing, although the question of how coordinated activity within these nuclei orchestrates reward valuation and consumption remains unclear. Inhibition of NAcSh firing is necessary for reward consumption, but the source of this inhibition remains unknown. Here, we report that a subpopulation of VP neurons, the ventral arkypallidal (vArky) neurons, project back to the NAcSh, where they inhibit NAcSh neurons in vivo in mice. Consistent with this pathway driving reward consumption via inhibition of the NAcSh, calcium activity of vArky neurons scaled with reward palatability (which was dissociable from reward seeking) and predicted the subsequent drinking behavior during a free-access paradigm. Activation of the VP-NAcSh pathway increased ongoing reward consumption while amplifying hedonic reactions to reward. These results establish a pivotal role for vArky neurons in the promotion of reward consumption through modulation of NAcSh firing in a value-dependent manner.


Assuntos
Potenciais de Ação/fisiologia , Prosencéfalo Basal/fisiologia , Inibição Neural/fisiologia , Neurônios/fisiologia , Recompensa , Animais , Cálcio/metabolismo , Comportamento de Ingestão de Líquido/fisiologia , Feminino , Masculino , Camundongos , Vias Neurais/fisiologia , Núcleo Accumbens/fisiologia , Paladar/fisiologia
12.
Nat Commun ; 12(1): 677, 2021 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-33514725

RESUMO

Neurotransmitter is released synchronously and asynchronously following an action potential. Our recent study indicates that the release sites of these two phases are segregated within an active zone, with asynchronous release sites enriched near the center in mouse hippocampal synapses. Here we demonstrate that synchronous and asynchronous release sites are aligned with AMPA receptor and NMDA receptor clusters, respectively. Computational simulations indicate that this spatial and temporal arrangement of release can lead to maximal membrane depolarization through AMPA receptors, alleviating the pore-blocking magnesium leading to greater activation of NMDA receptors. Together, these results suggest that release sites are likely organized to activate NMDA receptors efficiently.


Assuntos
Hipocampo/fisiologia , Modelos Neurológicos , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Transmissão Sináptica/fisiologia , Potenciais de Ação/fisiologia , Animais , Astrócitos , Células Cultivadas , Simulação por Computador , Feminino , Ácido Glutâmico/metabolismo , Hipocampo/citologia , Hipocampo/ultraestrutura , Masculino , Camundongos , Microscopia Eletrônica , Neurônios , Cultura Primária de Células , Análise Espaço-Temporal , Sinapses/metabolismo , Sinapses/ultraestrutura
13.
Nat Commun ; 12(1): 607, 2021 01 27.
Artigo em Inglês | MEDLINE | ID: mdl-33504797

RESUMO

Motor function depends on neural dynamics spanning multiple spatiotemporal scales of population activity, from spiking of neurons to larger-scale local field potentials (LFP). How multiple scales of low-dimensional population dynamics are related in control of movements remains unknown. Multiscale neural dynamics are especially important to study in naturalistic reach-and-grasp movements, which are relatively under-explored. We learn novel multiscale dynamical models for spike-LFP network activity in monkeys performing naturalistic reach-and-grasps. We show low-dimensional dynamics of spiking and LFP activity exhibited several principal modes, each with a unique decay-frequency characteristic. One principal mode dominantly predicted movements. Despite distinct principal modes existing at the two scales, this predictive mode was multiscale and shared between scales, and was shared across sessions and monkeys, yet did not simply replicate behavioral modes. Further, this multiscale mode's decay-frequency explained behavior. We propose that multiscale, low-dimensional motor cortical state dynamics reflect the neural control of naturalistic reach-and-grasp behaviors.


Assuntos
Comportamento Animal/fisiologia , Força da Mão/fisiologia , Córtex Motor/fisiologia , Potenciais de Ação/fisiologia , Animais , Macaca mulatta , Modelos Neurológicos , Análise e Desempenho de Tarefas
14.
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
15.
J Electromyogr Kinesiol ; 56: 102510, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33341461

RESUMO

It is necessary to decompose the intra-muscular EMG signal to extract motor unit action potential (MUAP) waveforms and firing times. Some algorithms were proposed in the literature to resolve superimposed MUAPs, including Peel-Off (PO), branch and bound (BB), genetic algorithm (GA), and particle swarm optimization (PSO). This study aimed to compare these algorithms in terms of overall accuracy and running time. Two sets of two-to-five MUAP templates (set1: a wide range of energies, and set2: a high degree of similarity) were used. Such templates were time-shifted, and white Gaussian noise was added. A total of 1000 superpositions were simulated for each template and were resolved using PO (also, POI: interpolated PO), BB, GA, and PSO algorithms. The generalized estimating equation was used to identify which method significantly outperformed, while the overall rank product was used for overall ranking. The rankings were PSO, BB, GA, PO, and POI in the first, and BB, PSO, GA, PO, POI in the second set. The overall ranking was BB, PSO, GA, PO, and POI in the entire dataset. Although the BB algorithm is generally fast, there are cases where the BB algorithm is too slow and it is thus not suitable for real-time applications.


Assuntos
Potenciais de Ação/fisiologia , Algoritmos , Eletromiografia/métodos , Neurônios Motores/fisiologia , Recrutamento Neurofisiológico/fisiologia , Processamento de Sinais Assistido por Computador , Humanos , Músculo Esquelético/fisiologia
16.
Nat Neurosci ; 24(2): 266-275, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33349710

RESUMO

Successfully navigating in physical or semantic space requires a neural representation of allocentric (map-based) vectors to boundaries, objects and goals. Cognitive processes such as path-planning and imagination entail the recall of vector representations, but evidence of neuron-level memory for allocentric vectors has been lacking. Here, we describe a novel neuron type, vector trace cell (VTC), whose firing generates a new vector field when a cue is encountered and a 'trace' version of that field for hours after cue removal. VTCs are concentrated in subiculum, distal to CA1. Compared to non-trace cells, VTCs fire at further distances from cues and exhibit earlier-going shifts in preferred theta phase in response to newly introduced cues, which demonstrates a theta-linked neural substrate for memory encoding. VTCs suggest a vector-based model of computing spatial relationships between an agent and multiple spatial objects, or between different objects, freed from the constraints of direct perception of those objects.


Assuntos
Potenciais de Ação/fisiologia , Hipocampo/citologia , Neurônios/citologia , Percepção Espacial/fisiologia , Animais , Sinais (Psicologia) , Hipocampo/fisiologia , Masculino , Neurônios/fisiologia , Ratos , Navegação Espacial/fisiologia
17.
J Neurol Sci ; 420: 117271, 2021 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-33359928

RESUMO

More than half of patients who recover from COVID-19 experience fatigue. We studied fatigue using neuropsychological and neurophysiological investigations in post-COVID-19 patients and healthy subjects. Neuropsychological assessment included: Fatigue Severity Scale (FSS), Fatigue Rating Scale, Beck Depression Inventory, Apathy Evaluation Scale, cognitive tests, and computerized tasks. Neurophysiological examination was assessed before (PRE) and 2 min after (POST) a 1-min fatiguing isometric pinching task and included: maximum compound muscle action potential (CMAP) amplitude in first dorsal interosseous muscle (FDI) following ulnar nerve stimulation, resting motor threshold, motor evoked potential (MEP) amplitude and silent period (SP) duration in right FDI following transcranial magnetic stimulation of the left motor cortex. Maximum pinch strength was measured. Perceived exertion was assessed with the Borg-Category-Ratio scale. Patients manifested fatigue, apathy, executive deficits, impaired cognitive control, and reduction in global cognition. Perceived exertion was higher in patients. CMAP and MEP were smaller in patients both PRE and POST. CMAP did not change in either group from PRE to POST, while MEP amplitudes declined in controls POST. SP duration did not differ between groups PRE, increased in controls but decreased in patients POST. Patients' change of SP duration from PRE to POST was negatively correlated to FSS. Abnormal SP shortening and lack of MEP depression concur with a reduction in post-exhaustion corticomotor inhibition, suggesting a possible GABAB-ergic dysfunction. This impairment might be related to the neuropsychological alterations. COVID-19-associated inflammation might lead to GABAergic impairment, possibly representing the basis of fatigue and explaining apathy and executive deficits.


Assuntos
Potenciais de Ação/fisiologia , Função Executiva/fisiologia , Fadiga/virologia , Músculo Esquelético/fisiopatologia , Idoso , Idoso de 80 Anos ou mais , /psicologia , Potencial Evocado Motor/fisiologia , Fadiga/fisiopatologia , Fadiga/psicologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Córtex Motor/fisiopatologia , Testes Neuropsicológicos , Estimulação Magnética Transcraniana
18.
PLoS One ; 15(12): e0244683, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33382788

RESUMO

With the continuous improvement of automation and informatization, the electromagnetic environment has become increasingly complex. Traditional protection methods for electronic systems are facing with serious challenges. Biological nervous system has the self-adaptive advantages under the regulation of the nervous system. It is necessary to explore a new thought on electromagnetic protection by drawing from the self-adaptive advantage of the biological nervous system. In this study, the scale-free spiking neural network (SFSNN) is constructed, in which the Izhikevich neuron model is employed as a node, and the synaptic plasticity model including excitatory and inhibitory synapses is employed as an edge. Under white Gaussian noise, the noise suppression abilities of the SFSNNs with the high average clustering coefficient (ACC) and the SFSNNs with the low ACC are studied comparatively. The noise suppression mechanism of the SFSNN is explored. The experiment results demonstrate that the following. (1) The SFSNN has a certain degree of noise suppression ability, and the SFSNNs with the high ACC have higher noise suppression performance than the SFSNNs with the low ACC. (2) The neural information processing of the SFSNN is the linkage effect of dynamic changes in neuron firing, synaptic weight and topological characteristics. (3) The synaptic plasticity is the intrinsic factor of the noise suppression ability of the SFSNN.


Assuntos
Potenciais de Ação/fisiologia , Modelos Neurológicos , Redes Neurais de Computação , Neurônios/fisiologia , Sinapses/fisiologia , Algoritmos , Plasticidade Neuronal/fisiologia
19.
Proc Natl Acad Sci U S A ; 117(52): 33639-33648, 2020 12 29.
Artigo em Inglês | MEDLINE | ID: mdl-33328274

RESUMO

Spike-timing-dependent plasticity (STDP) is considered as a primary mechanism underlying formation of new memories during learning. Despite the growing interest in activity-dependent plasticity, it is still unclear whether synaptic plasticity rules inferred from in vitro experiments are correct in physiological conditions. The abnormally high calcium concentration used in in vitro studies of STDP suggests that in vivo plasticity rules may differ significantly from in vitro experiments, especially since STDP depends strongly on calcium for induction. We therefore studied here the influence of extracellular calcium on synaptic plasticity. Using a combination of experimental (patch-clamp recording and Ca2+ imaging at CA3-CA1 synapses) and theoretical approaches, we show here that the classic STDP rule in which pairs of single pre- and postsynaptic action potentials induce synaptic modifications is not valid in the physiological Ca2+ range. Rather, we found that these pairs of single stimuli are unable to induce any synaptic modification in 1.3 and 1.5 mM calcium and lead to depression in 1.8 mM. Plasticity can only be recovered when bursts of postsynaptic spikes are used, or when neurons fire at sufficiently high frequency. In conclusion, the STDP rule is profoundly altered in physiological Ca2+, but specific activity regimes restore a classical STDP profile.


Assuntos
Cálcio/metabolismo , Plasticidade Neuronal/fisiologia , Potenciais de Ação/fisiologia , Animais , Potenciação de Longa Duração , Modelos Neurológicos , Dinâmica não Linear , Ratos Wistar , Fatores de Tempo
20.
PLoS Comput Biol ; 16(12): e1008503, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33347433

RESUMO

In this work, we introduce new phenomenological neuronal models (eLIF and mAdExp) that account for energy supply and demand in the cell as well as the inactivation of spike generation how these interact with subthreshold and spiking dynamics. Including these constraints, the new models reproduce a broad range of biologically-relevant behaviors that are identified to be crucial in many neurological disorders, but were not captured by commonly used phenomenological models. Because of their low dimensionality eLIF and mAdExp open the possibility of future large-scale simulations for more realistic studies of brain circuits involved in neuronal disorders. The new models enable both more accurate modeling and the possibility to study energy-associated disorders over the whole time-course of disease progression instead of only comparing the initially healthy status with the final diseased state. These models, therefore, provide new theoretical and computational methods to assess the opportunities of early diagnostics and the potential of energy-centered approaches to improve therapies.


Assuntos
Potenciais de Ação/fisiologia , Metabolismo Energético , Modelos Neurológicos , Animais , Encéfalo/metabolismo , Encéfalo/fisiologia , Humanos , Rede Nervosa , Doença de Parkinson/metabolismo , Doença de Parkinson/fisiopatologia , Convulsões/metabolismo , Convulsões/fisiopatologia , ATPase Trocadora de Sódio-Potássio/metabolismo
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