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1.
Mol Brain ; 15(1): 50, 2022 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-35672792

RESUMO

Theta is one of the most prominent extracellular synchronous oscillations in the mammalian brain. Hippocampal theta relies on an intact medial septum (MS) and has been consistently recorded during the training phase of some learning paradigms, suggesting that it may be implicated in hippocampus-dependent long-term memory processing. Object recognition memory (ORM) allows animals to identify familiar items and is essential for remembering facts and events. In rodents, long-term ORM formation requires a functional hippocampus but the involvement of the MS in this process remains controversial. We found that training adult male Wistar rats in a long-term ORM-inducing learning task involving exposure to two different, but behaviorally equivalent novel stimuli objects increased hippocampal theta power, and that suppressing theta via optogenetic MS inactivation caused amnesia. Importantly, the amnesia was specific to the object the animals were exploring when the MS was inactivated. Taken together, our results indicate that the MS is necessary for long-term ORM formation and suggest that hippocampal theta activity is causally linked to this process.


Assuntos
Optogenética , Ritmo Teta , Amnésia , Animais , Hipocampo/fisiologia , Masculino , Mamíferos , Memória de Longo Prazo , Optogenética/métodos , Ratos , Ratos Wistar , Ritmo Teta/fisiologia
2.
Neuron ; 110(12): 1884-1886, 2022 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-35709692

RESUMO

In this issue of Neuron, Szabo et al. uncover a unique subtype of interneurons that is highly active during ripples but largely silent during theta oscillations. The study provides exciting new insights into the regulation and propagation of ripples in CA1 and beyond.


Assuntos
Interneurônios , Células Piramidais , Potenciais de Ação/fisiologia , Hipocampo/fisiologia , Interneurônios/fisiologia , Neurônios/fisiologia , Células Piramidais/fisiologia , Ritmo Teta/fisiologia
3.
Trends Neurosci ; 45(7): 550-562, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35599065

RESUMO

The construction of complex engrams requires hippocampal-cortical interactions. These include both direct interactions and ones via often-overlooked subcortical loops. Here, we review the anatomical organization of a hierarchy of parallel 'Papez' loops through the hypothalamus that are homologous in mammals from rats to humans. These hypothalamic loops supplement direct hippocampal-cortical connections with iterative reprocessing paced by theta rhythmicity. We couple existing anatomy and lesion data with theory to propose that recirculation in these loops progressively enhances desired connections, while reducing interference from competing external goals and internal associations. This increases the signal-to-noise ratio in the distributed engrams (neocortical and cerebellar) necessary for complex learning and memory. The hypothalamic nodes provide key motivational input for engram enhancement during consolidation.


Assuntos
Hipocampo , Hipotálamo , Animais , Cerebelo , Humanos , Aprendizagem , Mamíferos , Vias Neurais/anatomia & histologia , Ratos , Ritmo Teta
4.
Brain Stimul ; 15(3): 833-842, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35636708

RESUMO

BACKGROUND: Theta burst stimulation (TBS) is an efficient noninvasive neuromodulation paradigm that has been widely adopted, clinically. However, the efficacy of TBS treatment remains similarly modest as conventional 10 Hz repetitive transcranial magnetic stimulation (rTMS). OBJECTIVE/HYPOTHESIS: To develop a new TBS paradigm that enhances the effects of TMS administration while maintaining high time-efficiency. METHODS: We describe here a new TMS paradigm, named High-Density Theta Burst Stimulation (hdTBS). This paradigm delivers up to 6 pulses per burst, as opposed to only 3 in conventional TBS, while maintaining the inter-burst interval of 200 ms (or 5 Hz) - a critical parameter in inducing long-term potentiation. This paradigm was implemented on a TMS stimulator developed in-house; its physiological effects were assessed in the motor cortex of awake rats using a rodent specific focal TMS coil. Microwire electrodes were implanted into each rat's limb muscles to longitudinally record motor-evoked potential (MEP). Four different TBS paradigms (3, 4, 5 or 6 pulses per burst, 200 s per session) were tested; MEP signals were recorded immediately before (baseline) and up to 35 min post each TBS session. RESULTS: We developed a stimulator based on a printed-circuit board strategy. The stimulator was able to deliver stable outputs of up to 6 pulses per burst. Animal experiments (n = 15) revealed significantly different aftereffects induced by the four TBS paradigms (Friedman test, p = 0.018). Post hoc analysis further revealed that, in comparison to conventional 3-pulse TBS, 5- and 6-pulse TBS enhanced the aftereffects of MEP signals by 56% and 92%, respectively, while maintaining identical time efficiency. CONCLUSION(S): A new stimulation paradigm is proposed, implemented and tested in the motor cortex of awake rats using a focal TMS coil developed in the lab. We observed enhanced aftereffects as assessed by MEP, with no obvious adverse effects, suggesting the translational potentials of this paradigm.


Assuntos
Córtex Motor , Estimulação Magnética Transcraniana , Animais , Potencial Evocado Motor/fisiologia , Potenciação de Longa Duração , Córtex Motor/fisiologia , Músculo Esquelético/fisiologia , Ratos , Ritmo Teta/fisiologia
5.
Sci Rep ; 12(1): 8869, 2022 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-35614196

RESUMO

The use of haptic technologies in modern life scenarios is becoming the new normal particularly in rehabilitation, medical training, and entertainment applications. An evident challenge in haptic telepresence systems is the delay in haptic information. How humans perceive delayed visual and audio information has been extensively studied, however, the same for haptically delayed environments remains largely unknown. Here, we develop a visuo-haptic experimental setting that simulates pick and place task and involves continuous haptic feedback stimulation with four possible haptic delay levels. The setting is built using a haptic device and a computer screen. We use electroencephalography (EEG) to study the neural correlates that could be used to identify the amount of the experienced haptic delay. EEG data were collected from 34 participants. Results revealed that midfrontal theta oscillation plays a pivotal role in quantifying the amount of haptic delay while parietal alpha showed a significant modulation that encodes the presence of haptic delay. Based on the available literature, these results suggest that the amount of haptic delay is proportional to the neural activation that is associated with conflict detection and resolution as well as for multi-sensory divided attention.


Assuntos
Ritmo Teta , Atenção , Eletroencefalografia , Retroalimentação , Humanos , Ritmo Teta/fisiologia
6.
Neuroimage ; 256: 119264, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-35508215

RESUMO

Both conflict and error processing have been linked to the midfrontal theta power (4-8 Hz) increase as indicated by EEG studies and greater hemodynamic activity in the anterior midcingulate cortex (aMCC) as indicated by fMRI studies. Conveniently, the source of the midfrontal theta power was estimated in or nearby aMCC. However, previous studies using concurrent EEG and fMRI recordings in resting-state or other cognitive tasks observed only a negative relationship between theta power and BOLD signal in the brain regions typically showing task-related deactivations. In this study, we used a simultaneous EEG-fMRI technique to investigate a trial-by-trial coupling between theta power and hemodynamic activity during the performance of two conflict tasks. Independent component analysis (ICA) was applied to denoise the EEG signal and select individual midfrontal EEG components, whereas group ICA was applied to fMRI data to obtain a functional parcellation of the frontal cortex. Using a linear mixed-effect model, theta power was coupled with the peak of hemodynamic responses from various frontal, cingulate, and insular cortical sites to unravel the potential brain sources that contribute to conflict- and error-related theta variability. Although several brain regions exhibited conflict-related increases in hemodynamic activity, the conflict pre-response theta showed only a negative correlation to BOLD signal in the midline area 9 (MA9), a region exhibiting conflict-sensitive deactivation. Conversely, and more expectedly, error-related theta showed a positive relationship to activity in the aMCC. Our results provide novel evidence suggesting that the amplitude of pre-response theta reflects the process of active inhibition that suppresses the MA9 activity. This process is affected independently by the stimulus congruency, reaction times variance, and is susceptible to the time-on-task effect. Finally, it predicts the commitment of an omission error. Together, our findings highlight that conflict- and error-related theta oscillations represent fundamentally different processes.


Assuntos
Encéfalo , Ritmo Teta , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Eletroencefalografia , Lobo Frontal/diagnóstico por imagem , Lobo Frontal/fisiologia , Humanos , Imageamento por Ressonância Magnética , Ritmo Teta/fisiologia
7.
Exp Neurol ; 354: 114106, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35526596

RESUMO

Dopamine modulation is thought to underpin some of the therapeutic effects associated with repetitive transcranial magnetic stimulation (rTMS). However, patient studies have failed to demonstrate consistent changes in the dopamine system in vivo after a therapeutic course of rTMS. Here, we evaluated acute and chronic changes in striatal dopamine release elicited by a clinically relevant course of theta burst (TBS) or sham stimulation using [11C]raclopride in healthy non-human primates (n = 11). Subjects were scanned immediately after the first session of TBS and the day after a 3 week course of daily TBS delivery. After experiment completion, animals were euthanized, and immunofluorescence staining was carried out using antibodies targeting D2 receptors (D2R). Continuous TBS (cTBS, an inhibitory form of rTMS) over the left primary motor cortex acutely decreased dopamine release bilaterally in the putamen. However, no significant changes in dopamine receptors nor D2R immunoreactivity were noted 24 h after the last stimulation, while a decrease in cortical excitability, as measured by an increase in resting motor threshold, could still be quantified. On the opposite, intermittent TBS (iTBS, an excitatory form of rTMS) did not affect dopamine release, acutely or chronically, D2R immunoreactivity or cortical excitability. These findings suggest that the long-term therapeutic effects of TBS might be facilitated through the modulation of different neurotransmission systems beyond the dopamine system. However, given the small sample size, these results should be interpreted with caution.


Assuntos
Excitabilidade Cortical , Estimulação Magnética Transcraniana , Animais , Dopamina , Potencial Evocado Motor/fisiologia , Humanos , Ritmo Teta/fisiologia , Estimulação Magnética Transcraniana/métodos
8.
Neural Plast ; 2022: 3593262, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35529454

RESUMO

Background: Various forms of theta-burst stimulation (TBS) such as intermittent TBS (iTBS) and continuous TBS (cTBS) have been introduced as novel facilitation/suppression schemes during repetitive transcranial magnetic stimulation (rTMS), demonstrating a better efficacy than conventional paradigms. Herein, we extended the rTMS-TBS schemes to electrical stimulation of high-definition montage (HD-TBS) and investigated its neural effects on the human brain. Methods: In a within-subject design, fifteen right-handed healthy adults randomly participated in 10 min and 2 mA HD-TBS sessions: unilateral (Uni)-iTBS, bilateral (Bi)-cTBS/iTBS, and sham stimulation over primary motor cortex regions. A 20-channel near-infrared spectroscopy (NIRS) system was covered on the bilateral prefrontal cortex (PFC), sensory motor cortex (SMC), and parietal lobe (PL) for observing cerebral hemodynamic responses in the resting-state and during fast finger-tapping tasks at pre-, during, and poststimulation. Interhemispheric correlation coefficient (IHCC) and wavelet phase coherence (WPCO) from resting-state NIRS and concentration of oxyhemoglobin during fast finger-tapping tasks were explored to reflect the symmetry between the two hemispheres and cortical activity, respectively. Results: The IHCC and WPCO of NIRS data in the SMC region under Bi-cTBS/iTBS showed relatively small values at low-frequency bands III (0.06-0.15 Hz) and IV (0.02-0.06), indicating a significant desynchronization in both time and frequency domains. In addition, the SMC activation induced by fast finger-tapping exercise was significantly greater during Uni-iTBS as well as during and post Bi-cTBS/iTBS sessions. Conclusions: It appears that a 10 min and 2 mA Bi-cTBS/iTBS applied over two hemispheres within the primary motor cortex region could effectively modulate the interhemispheric synchronization and cortical activation in the SMC of healthy subjects. Our study demonstrated that bilateral HD-TBS approaches is an effective noninvasive brain stimulation scheme which could be a novel therapeutic for inducing effects of neuromodulation on various neurological disorders caused by ischemic stroke or traumatic brain injuries.


Assuntos
Lobo Parietal , Estimulação Magnética Transcraniana , Adulto , Estimulação Elétrica , Potencial Evocado Motor/fisiologia , Voluntários Saudáveis , Humanos , Córtex Pré-Frontal/fisiologia , Ritmo Teta/fisiologia , Estimulação Magnética Transcraniana/métodos
9.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 39(2): 267-275, 2022 Apr 25.
Artigo em Chinês | MEDLINE | ID: mdl-35523547

RESUMO

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.


Assuntos
Memória de Curto Prazo , Estimulação Transcraniana por Corrente Contínua , Acústica , Animais , Estimulação Elétrica , Memória de Curto Prazo/fisiologia , Ratos , Ratos Wistar , Ritmo Teta/fisiologia
10.
Curr Biol ; 32(10): R479-R481, 2022 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-35609549

RESUMO

New research suggests that frontal midline theta EEG activity in humans controls activity in parietal cortex associated with memory maintenance. In turn, the speed of this frontal theta is modulated by the number of items to be handled, potentially indicating strong bidirectional communication within a fronto-parietal network.


Assuntos
Memória de Curto Prazo , Lobo Parietal , Encéfalo , Eletroencefalografia , Lobo Frontal , Humanos , Ritmo Teta
11.
Elife ; 112022 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-35532116

RESUMO

The hippocampus is known to play a critical role in processing information about temporal context. However, it remains unclear how hippocampal oscillations are involved, and how their functional organization is influenced by connectivity gradients. We examined local field potential activity in CA1 as rats performed a nonspatial odor sequence memory task. We found that odor sequence processing epochs were characterized by distinct spectral profiles and proximodistal CA1 gradients of theta and 20-40 Hz power than track running epochs. We also discovered that 20-40 Hz power was predictive of sequence memory performance, particularly in proximal CA1 and during the plateau of high power observed in trials in which animals had to maintain their decision until instructed to respond. Altogether, these results provide evidence that dynamics of 20-40 Hz power along the CA1 axis are linked to trial-specific processing of nonspatial information critical to order judgments and are consistent with a role for 20-40 Hz power in gating information processing.


Assuntos
Hipocampo , Memória , Animais , Região CA1 Hipocampal , Cognição , Odorantes , Ratos , Ritmo Teta
12.
Exp Neurol ; 354: 114110, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35551900

RESUMO

Cortical oscillations in different frequency bands have been shown to be intimately involved in exploration of environment and cognition. Here, the local field potentials in the hippocampus, the medial prefrontal cortex (mPFC), and the medial entorhinal cortex (mEC) were recorded simultaneously in rats during the execution of the episodic-like memory task. The power of theta (~4-10 Hz), slow gamma (~25-50 Hz), and fast gamma oscillations (~55-100 Hz) was analyzed in all structures examined. Particular attention was paid to the theta coherence between three mentioned structures. The modulation of the power of gamma rhythms by the phase of theta cycle during the execution of the episodic-like memory test by rats was also closely studied. Healthy rats and rats one month after kainate-induced status epilepticus (SE) were examined. Paroxysmal activity in the hippocampus (high amplitude interictal spikes), excessive excitability of animals, and the death of hippocampal and dentate granular cells in rats with kainate-evoked SE were observed, which indicated the development of seizure focus in the hippocampus (epileptogenesis). One month after SE, the rats exhibited a specific impairment of episodic memory for the what-where-when triad: unlike healthy rats, epileptogenic SE animals did not identify the objects during the test. This impairment was associated with the changes in the characteristics of theta and gamma rhythms and specific violation of theta coherence and theta/gamma coupling in these structures in comparison with the healthy animals. We believe that these disturbances in the cortical areas play a role in episodic memory dysfunction in kainate-treated animals. These findings can shed light on the mechanisms of cognitive deficit during epileptogenesis.


Assuntos
Neocórtex , Estado Epiléptico , Animais , Ritmo Gama , Hipocampo/fisiologia , Ácido Caínico/toxicidade , Ratos , Ritmo Teta/fisiologia
13.
Cortex ; 152: 122-135, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35569325

RESUMO

Inhibition of inappropriate behavior is relevant in many everyday situations. Nevertheless, the mechanisms that induce response inhibition based on sensory information and what influences these mechanisms are not entirely understood. We examined neurophysiological processes of perception-action integration in response inhibition and the impact of the pre-trial neurophysiological functional connectivity state in the theta and alpha band on these integration processes. The study was motivated by the Theory of Event Coding framework. Within the trial, fronto-medial theta band activity and occipital alpha band activity revealed an opposing interplay depending on the necessity of (re-)binding event files, i.e., the disintegration and recombination of stimulus-response associations, during response inhibition. When response inhibition required the reconfiguration of event files, this was associated with increased theta band activity but lower alpha band activity, and vice versa for the retrieval of event files. Notably, the most substantial impact of pre-trial connectivity on the within-trial event file binding effect (the difference between conditions that require reconfiguration and those that do not) during response inhibition occurred between fronto-medial areas and areas of the ventral stream in the theta frequency band. This suggests a preparatory top-down control of sensory areas before stimulus presentation. Increased pre-trial connectivity was associated with a decreased event file binding effect in the alpha frequency band and an increased event file binding effect in the theta frequency band during response inhibition. This implies an impact of the pre-trial functional connectivity state on inhibitory gating processes of relevant information and event file (re-)binding during response inhibition. The study shows how perception-action integration during response inhibition is affected by preceding transient neurophysiological connectivity states.


Assuntos
Eletroencefalografia , Inibição Psicológica , Humanos , Percepção , Ritmo Teta/fisiologia
14.
J Neurophysiol ; 127(6): 1532-1534, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35544758

RESUMO

Theta burst stimulation (TBS), a specific version of transcranial magnetic stimulation (TMS), is known to induce long-term plasticity of the brain with a short-term administration. Although many studies and treatments have increasingly used TBS as a neuromodulation tool, its reliability is still in question. This article reviews a study by Boucher et al. (Boucher PO, Ozdemir RA, Momi D, Burke MJ, Jannati A, Fried PJ, Pascual-Leone A, Shafi MM, Santarnecchi E. Sci Rep 11: 21170, 2021) that found minimal reliability of TBS by examining different TBS protocols (intermittent/continuous/sham) and considers possible alternative explanations for the variability of TBS effects.


Assuntos
Gastrópodes , Estimulação Magnética Transcraniana , Animais , Encéfalo/fisiologia , Reprodutibilidade dos Testes , Ritmo Teta/fisiologia , Estimulação Magnética Transcraniana/métodos
15.
Exp Gerontol ; 163: 111808, 2022 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-35429591

RESUMO

It is known that anxiety has a lot of comorbidity such as depression and may cause older subjects to be more prone to anxiety. Animal studies have also observed that older rats have lower movement in different situations, somewhat like anxiety symptoms (avoidance and freezing). The anxiety level of rodents is commonly evaluated using the elevated plus maze test, and videos are often used to record and quantify the activities of animals during the test. Furthermore, aging can reduce the frequency and activity of locomotion-induced hippocampal theta rhythm, and these reductions are also reflected in sensory-motor integration and cognition. Thus, directly analyzing the hippocampal theta rhythm and the quantity and quality of physical activity (PA) during the anxiety test can help elucidate the mechanisms underlying the anxiety-like behaviour. We explored alterations in the hippocampal theta rhythm, PA, and behavioural consistency (cross-correlation with 8-s window length) from triaxial acceleration vectors and subsequently examined the effects of age during the elevated plus maze test. We hypothesized that middle-aged rats would exhibit more anxiety, which is correlated with a reduction in behavioural consistency and hippocampal theta frequency during the elevated plus maze test. The middle-aged rats had a lower open-arm frequency and more low-frequency theta oscillations. The middle-aged rats had a lower mean power frequency (Frq) of the hippocampal theta rhythm, PA, and behavioural consistency. The Frq of the middle-aged rats was positively correlated with behavioural consistency. The results indicated that behavioural consistency could distinguish age-related anxiety-like behaviour. Behavioural consistency can serve as an index for the quality of movement and be used to distinguish age-related anxiety.


Assuntos
Escala de Avaliação Comportamental , Ritmo Teta , Animais , Ansiedade , Transtornos de Ansiedade , Hipocampo , Humanos , Ratos
17.
eNeuro ; 9(2)2022.
Artigo em Inglês | MEDLINE | ID: mdl-35396256

RESUMO

θ-Scale coordination of prelimbic medial prefrontal cortex (mPFC) local field potentials (LFPs) and its influence via direct or indirect projections to the ventral hippocampus (vHC) and dorsal hippocampus (dHC) during spatial learning remains poorly understood. We hypothesized that θ frequency coordination dynamics within and between the mPFC, dHC, and vHC would be predetermined by the level of connectivity rather than reflecting differing circuit throughput relationships depending on cognitive demands. Moreover, we hypothesized that coherence levels would not change during learning of a complex spatial avoidance task. Adult male rats were bilaterally implanted with EEG electrodes and LFPs recorded in each structure. Contrary to predictions, θ coherence averaged across "Early" or "Late" training sessions in the mPFC-HC, mPFC-mPFC, and HC-HC increased as a function of task learning. Coherence levels were also highest between the indirectly connected mPFC-dHC circuit, particularly during early training. Although mPFC postacquisition coherence remained higher with dHC than vHC, dynamic mPFC coherence patterns with both hippocampal poles across avoidance epochs were similar. In the 3 s before avoidance, a regional temporal sequence of transitory coherence peaks emerged between the mPFC-mPFC, the mPFC-HC, and then dHC-dHC. During this sequence, coherence within θ bandwidth fluctuated between epochs at distinct subfrequencies, suggesting frequency-specific roles for the propagation of task-relevant processing. On a second timescale, coherence frequency within and between the mPFC and hippocampal septotemporal axis change as a function of avoidance learning and cognitive demand. The results support a role for θ coherence subbandwidths, and specifically an 8- to 9-Hz mPFC θ signal, for generating and processing qualitatively different types of information in the organization of spatial avoidance behavior in the mPFC-HC circuit.


Assuntos
Córtex Pré-Frontal , Ritmo Teta , Animais , Aprendizagem da Esquiva , Eletroencefalografia , Hipocampo , Masculino , Ratos
18.
Exp Brain Res ; 240(5): 1565-1578, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35359173

RESUMO

Non-invasive theta burst stimulation (TBS) can elicit facilitatory or inhibitory changes in the central nervous system when applied intermittently (iTBS) or continuously (cTBS). Conversely, neuromuscular electrical stimulation (NMES) can activate the muscles to send a sensory volley, which is also known to affect the excitability of the central nervous system. We investigated whether cortical iTBS (facilitatory) or cTBS (inhibitory) priming can affect subsequent NMES-induced corticospinal excitability. A total of six interventions were tested, each with 11 able-bodied participants: cortical priming followed by NMES (iTBS + NMES and cTBS + NMES), NMES only (iTBSsham + NMES and cTBSsham + NMES), and cortical priming only (iTBS + rest and cTBS + rest). After iTBS or cTBS priming, NMES was used to activate right extensor capri radialis (ECR) muscle intermittently for 10 min (5 s ON/5 s OFF). Single-pulse transcranial magnetic stimulation motor evoked potentials (MEPs) and maximum motor response (Mmax) elicited by radial nerve stimulation were compared before and after each intervention for 30 min. Our results showed that associative facilitatory iTBS + NMES intervention elicited greater MEP facilitation that lasted for at least 30 min after the intervention, while none of the interventions alone were effective to produce effects. We conclude that facilitatory iTBS priming can make the central nervous system more susceptible to changes elicited by NMES through sensory recruitment to enhance facilitation of corticospinal plasticity, while cTBS inhibitory priming efficacy could not be confirmed.


Assuntos
Córtex Motor , Estimulação Magnética Transcraniana , Estimulação Elétrica , Potencial Evocado Motor/fisiologia , Humanos , Córtex Motor/fisiologia , Músculos , Plasticidade Neuronal/fisiologia , Ritmo Teta/fisiologia , Estimulação Magnética Transcraniana/métodos , Extremidade Superior
19.
Curr Biol ; 32(10): 2121-2129.e3, 2022 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-35385693

RESUMO

How does the human brain manage multiple bits of information to guide goal-directed behavior? Successful working memory (WM) functioning has consistently been linked to oscillatory power in the theta frequency band (4-8 Hz) over fronto-medial cortex (fronto-medial theta [FMT]). Specifically, FMT is thought to reflect the mechanism of an executive sub-system that coordinates maintenance of memory contents in posterior regions. However, direct evidence for the role of FMT in controlling specific WM content is lacking. Here, we collected high-density electroencephalography (EEG) data while participants engaged in WM-dependent tasks and then used multivariate decoding methods to examine WM content during the maintenance period. Engagement of WM was accompanied by a focal increase in FMT. Importantly, decoding of WM content was driven by posterior sites, which, in turn, showed increased functional theta coupling with fronto-medial channels. Finally, we observed a significant slowing of FMT frequency with increasing WM load, consistent with the hypothesized broadening of a theta "duty cycle" to accommodate additional WM items. Together, these findings demonstrate that frontal theta orchestrates posterior maintenance of WM content. Moreover, the observed frequency slowing elucidates the function of FMT oscillations by specifically supporting phase-coding accounts of WM.


Assuntos
Memória de Curto Prazo , Ritmo Teta , Encéfalo , Mapeamento Encefálico , Eletroencefalografia , Humanos
20.
J Neurosci ; 42(20): 4187-4201, 2022 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35396329

RESUMO

Spatial memory and reward processing are known to be disrupted in schizophrenia. Since the lateral septum (LS) may play an important role in the integration of location and reward, we examined the effect of maternal immune activation (MIA), a known schizophrenia risk factor, on spatial representation in the rat LS. In support of a previous study, we found that spatial location is represented as a phase code in the rostral LS of adult male rats, so that LS cell spiking shifts systematically against the phase of the hippocampal, theta-frequency, local field potential as an animal moves along a track toward a reward (phase precession). Whereas shallow precession slopes were observed in control group cells, they were steeper in the MIA animals, such that firing frequently precessed across several theta cycles as the animal moved along the length of the apparatus, with subsequent ambiguity in the phase representation of location. Furthermore, an analysis of the phase trajectories of the control group cells revealed that the population tended to converge toward a common firing phase as the animal approached the reward location. This suggested that phase coding in these cells might signal both reward location and the distance to reward. By comparison, the degree of phase convergence in the MIA-group cells was weak, and the region of peak convergence was distal to the reward location. These findings suggest that a schizophrenia risk factor disrupts the phase-based encoding of location-reward relationships in the LS, potentially smearing reward representations across space.SIGNIFICANCE STATEMENT It is unclear how spatial or contextual information generated by hippocampal cells is converted to a code that can be used to signal reward location in regions, such as the VTA. Here we provide evidence that the firing phase of cells in the lateral septum, a region that links the two areas, may code reward location in the firing phase of cells. This phase coding is disrupted in a maternal immune activation model of schizophrenia risk such that representations of reward may be smeared across space in maternal immune activation animals. This could potentially underlie erroneous reward processing and misattribution of salience in schizophrenia.


Assuntos
Esquizofrenia , Potenciais de Ação/fisiologia , Animais , Hipocampo/fisiologia , Masculino , Ratos , Recompensa , Ritmo Teta/fisiologia
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