Publications

Closed-loop brain stimulation augments fear extinction in male rats

2023, NAT COMM 14:3972

Sierra RA, Pedraza LK, Barcsai L, Pejin A, Li Q, Kozák G, Takeuchi Y, Nagy AJ, Lőrincz ML, Devinsky O, Buzsáki G, Berényi A

<p>Dysregulated fear reactions can result from maladaptive processing of trauma-related memories. In post-traumatic stress disorder (PTSD) and other psychiatric disorders, dysfunctional extinction learning prevents discretization of trauma-related memory engrams and generalizes fear responses. Although PTSD may be viewed as a memory-based disorder, no approved treatments target pathological fear memory processing. Hippocampal sharp wave-ripples (SWRs) and concurrent neocortical oscillations are scaffolds to consolidate contextual memory, but their role during fear processing remains poorly understood. Here, we show that closed-loop, SWR triggered neuromodulation of the medial forebrain bundle (MFB) can enhance fear extinction consolidation in male rats. The modified fear memories became resistant to induced recall (i.e., ‘renewal’ and ‘reinstatement’) and did not reemerge spontaneously. These effects were mediated by D2 receptor signaling-induced synaptic remodeling in the basolateral amygdala. Our results demonstrate that SWR-triggered closed-loop stimulation of the MFB reward system enhances extinction of fearful memories and reducing fear expression across different contexts and preventing excessive and persistent fear responses. These findings highlight the potential of neuromodulation to augment extinction learning and provide a new avenue to develop treatments for anxiety disorders.</p>

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Reinstating olfactory bulb deri- ved limbic gamma oscillations alleviates depression-like behavioral deficits in rodents

2023, NEURON 111:1-11

Li Q, Takeuchi Y, Jiale Wang J, Gellért L, Barcsai L, Pedraza LK, Nagy AJ, Kozák G, Nakai S, Kato S, Kobayashi K, Ohsawa M, Horváth G, Kékesi G, Lőrincz ML, Devinsky OD, Buzsáki G, Berényi A

<p>Although the etiology of major depressive disorder remains poorly understood, reduced gamma oscillations is an emerging biomarker. Olfactory bulbectomy, an established model of depression that reduces limbic gamma oscillations, suffers from non-specific effects of structural damage. Here, we show that transient functional suppression of olfactory bulb neurons or their piriform cortex efferents decreased gamma oscillation power in limbic areas and induced depression-like behaviors in rodents. Enhancing transmission of gamma oscillations from olfactory bulb to limbic structures by closed-loop electrical neuromodulation alleviated these behaviors. By contrast, silencing gamma transmission by anti-phase closed-loop stimulation strengthened depression-like behaviors in naive animals. These induced behaviors were neutralized by ketamine treatment that restored limbic gamma power. Taken together, our results reveal a causal link between limbic gamma oscillations and depression-like behaviors in rodents. Interfering with these endogenous rhythms can affect behaviors in rodent models of depression, suggesting that restoring gamma oscillations may alleviate depressive symptoms.</p>

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Higher-order thalamic nuclei facilitate the generalization and maintenance of spike-and-wave discharges of absence seizures

2023, Neurob. of Dis. 178:106025

Atherton Z, Nagy O, Barcsai L, Sere P, Zsigri N, Földi T, Gellért L, Berényi A, Crunelli V, Lőrincz ML

<p>Spike-and-wave discharges (SWDs), generated by the cortico-thalamo-cortical (CTC) network, are pathological, large amplitude oscillations and the hallmark of <a class='topic-link' title='Learn more about absence seizures from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/absence-seizure'>absence seizures</a> (ASs). SWDs begin in a cortical initiation network in both humans and animal models, including the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), where it is located in the primary <a class='topic-link' title='Learn more about somatosensory cortex from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/somatosensory-cortex'>somatosensory cortex</a> (S1). The behavioral manifestation of an AS occurs when SWDs spread from the cortical initiation site to the whole brain, however, the mechanisms behind this rapid propagation remain unclear. Here we investigated these processes beyond the principal CTC network, in higher-order (HO) thalamic nuclei (lateral posterior (LP) and posterior (PO) nuclei) since their diffuse connectivity and known facilitation of intracortical communications make these nuclei key candidates to support SWD generation and maintenance. In freely moving GAERS, multi-site LFP in LP, PO and multiple cortical regions revealed a novel feature of SWDs: during SWDs there are short periods (named SWD-breaks) when cortical regions far from S1, such the primary <a class='topic-link' title='Learn more about visual cortex from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/visual-cortex'>visual cortex</a> (V1), become transiently unsynchronized from the ongoing EEG rhythm. Inactivation of HO nuclei with local <a class='topic-link' title='Learn more about muscimol from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/muscimol'>muscimol</a> injections or <a class='topic-link' title='Learn more about optogenetic from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/optogenetics'>optogenetic</a> perturbation of HO nuclei activity increased the occurrence of SWD-breaks and the former intervention also increased the SWD propagation-time from S1. The neural underpinnings of these findings were explored further by silicon probe recordings from single units of PO which uncovered two previously unknown groups of excitatory neurons based on their burst firing dynamics at SWD onset. Moreover, a switch from tonic to burst firing at SWD onset was shown to be an important feature since it was much less prominent for non-generalized events, i.e. SWDs that remained local to S1. Additionally, one group of neurons showed a reverse of this switch during SWD-breaks, demonstrating the importance of this firing pattern throughout the SWD. In summary, these results support the view that multiple HO thalamic nuclei are utilized at SWD onset and contribute to cortical synchrony throughout the paroxysmal discharge.</p>

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Temporally targeted interactions with pathologic oscillations as therapeutical targets in epilepsy and beyond

2021, FRONT. NEURAL CIRCUITS 15:784085

Földi T, Lőrincz ML, Berényi A

<p>Self-organized neuronal oscillations rely on precisely orchestrated ensemble activity in reverberating neuronal networks. Chronic, non-malignant disorders of the brain are often coupled to pathological neuronal activity patterns. In addition to the characteristic behavioral symptoms, these disturbances are giving rise to both transient and persistent changes of various brain rhythms. Increasing evidence support the causal role of these “oscillopathies” in the phenotypic emergence of the disease symptoms, identifying neuronal network oscillations as potential therapeutic targets. While the kinetics of pharmacological therapy is not suitable to compensate the disease related fine-scale disturbances of network oscillations, external biophysical modalities (e.g., electrical stimulation) can alter spike timing in a temporally precise manner. These perturbations can warp rhythmic oscillatory patterns via resonance or entrainment. Properly timed phasic stimuli can even switch between the stable states of networks acting as multistable oscillators, substantially changing the emergent oscillatory patterns. Novel transcranial electric stimulation (TES) approaches offer more reliable neuronal control by allowing higher intensities with tolerable side-effect profiles. This precise temporal steerability combined with the non- or minimally invasive nature of these novel TES interventions make them promising therapeutic candidates for functional disorders of the brain. Here we review the key experimental findings and theoretical background concerning various pathological aspects of neuronal network activity leading to the generation of epileptic seizures. The conceptual and practical state of the art of temporally targeted brain stimulation is discussed focusing on the prevention and early termination of epileptic seizures.</p>

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The Medial Septum as a Potential Target for Treating Brain Disorders Associated With Oscillopathies

2021, FRONT. NEURAL CIRCUITS 15:701080

Takeuchi Y, Nagy AJ, Barcsai L, Li Q, Ohsawa M, Mizuseki K, Berényi A

<p>The medial septum (MS), as part of the basal forebrain, supports many physiological functions, from sensorimotor integration to cognition. With often reciprocal connections with a broad set of peers at all major divisions of the brain, the MS orchestrates oscillatory neuronal activities throughout the brain. These oscillations are critical in generating sensory and emotional salience, locomotion, maintaining mood, supporting innate anxiety, and governing learning and memory. Accumulating evidence points out that the physiological oscillations under septal influence are frequently disrupted or altered in pathological conditions. Therefore, the MS may be a potential target for treating neurological and psychiatric disorders with abnormal oscillations (oscillopathies) to restore healthy patterns or erase undesired ones. Recent studies have revealed that the patterned stimulation of the MS alleviates symptoms of epilepsy. We discuss here that stimulus timing is a critical determinant of treatment efficacy on multiple time scales. On-demand stimulation may dramatically reduce side effects by not interfering with normal physiological functions. A precise pattern-matched stimulation through adaptive timing governed by the ongoing oscillations is essential to effectively terminate pathological oscillations. The time-targeted strategy for the MS stimulation may provide an effective way of treating multiple disorders including Alzheimer’s disease, anxiety/fear, schizophrenia, and depression, as well as pain.</p>

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Reduced MC4R signaling alters nociceptive thresholds associated with red hair

2021, SCI ADV 7(14):eabd1310

Robinson KC, Kemeny LV, Fell GL, Hermann AL, Allouche J, Ding W, Yekkirala A, Hsiao JJ, Su MY, Theodosakis N, Kozak G, Yuichi Takeuchi Y, Shen S, Berényi A, Mao J, Woolf CJ, Fisher D

<p>Humans and mice with natural red hair have elevated basal pain thresholds and an increased sensitivity to opioid analgesics. We investigated the mechanisms responsible for higher nociceptive thresholds in red-haired mice resulting from a loss of melanocortin 1 receptor (MC1R) function and found that the increased thresholds are melanocyte dependent but melanin independent. MC1R loss of function decreases melanocytic proopiomelanocortin transcription and systemic melanocyte-stimulating hormone (MSH) levels in the plasma of red-haired (<i>Mc1r<sup>e/e</sup></i>) mice. Decreased peripheral α-MSH derepresses the central opioid tone mediated by the opioid receptor OPRM1, resulting in increased nociceptive thresholds. We identified MC4R as the MSH-responsive receptor that opposes OPRM1 signaling and the periaqueductal gray area in the brainstem as a central area of opioid/melanocortin antagonism. This work highlights the physiologic role of melanocytic MC1R and circulating melanocortins in the regulation of nociception and provides a mechanistic framework for altered opioid signaling and pain sensitivity in red-haired individuals.</p>

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Closed-loop stimulation of the medial septum terminates epileptic seizures

2021, Brain 144(3):885–908

Takeuchi Y, Harangozo M, Pedraza L, Foldi T, Kozak G, Li Q, Berényi A

<p>Temporal lobe epilepsy with distributed hippocampal seizure foci is often intractable and its secondary generalization might lead to sudden death. Early termination through spatially extensive hippocampal intervention is not feasible directly, because of the large size and irregular shape of the hippocampus. In contrast, the medial septum is a promising target to govern hippocampal oscillations through its divergent connections to both hippocampi. Combining this ‘proxy intervention’ concept and precisely timed stimulation, we report here that closed-loop medial septum electrical stimulation can quickly terminate intrahippocampal seizures and suppress secondary generalization in a rat kindling model. Precise stimulus timing governed by internal seizure rhythms was essential. Cell type-specific stimulation revealed that the precisely timed activation of medial septum GABAergic neurons underlaid the effects. Our concept of time-targeted proxy stimulation for intervening pathological oscillations can be extrapolated to other neurological and psychiatric disorders, and has potential for clinical translation.</p>

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Oscillotherapeutics–Time-targeted interventions in epilepsy and beyond

2020, NEUROSCI RES 152:87-107

Takeuchi Y, Berényi A

<p>Oscillatory brain activities support many physiological functions from motor controlto cognition. Disruptions of the normal oscillatory brain activities are commonly observed in neurological and psychiatric disorders including epilepsy, Parkinson’s disease, Alzheimer’s disease, schizophrenia, anxiety/traumarelated disorders, major depressive disorders, and drug addiction. Therefore, these disorders can be considered as common oscillation defects despite having distinct behavioral manifestations and genetic causes. Recent technical advances of neuronal activity recording and analysis have allowed us to study the pathological oscillations of each disorder as a possible biomarker of symptoms. Furthermore, recent advances in brain stimulation technologies enable time- and space-targeted interventions of the pathological oscillations of both neurological disorders and psychiatric disorders as possible targets for regulating their symptoms.</p>

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Spike and wave discharges are not pathological sleep spindles - network-level aspects of age dependent absence seizure development in rats

2020, eNeuro 7(1):1–15

Kozák G, Földi T, Berényi A

<p>Spike-and-wave discharges (SWDs) of absence epilepsy are considered as pathologic alterations of sleep spindles; however, their network-level relationship has never been convincingly revealed. In order to observe the development and generalization of the thalamocortical SWDs and the concomitant alterations of sleep related oscillations, we performed local field potential (LFP) and single unit recordings in rats for three months during their maturation. We found that while SWDs and spindles look similar in young, they become different with maturation and shift to appear in different brain states. Thus, despite being generated by the same network, they are likely two distinct manifestations of the thalamocortical activity. We show that while spindles are already mainly global oscillations, SWDs appear mainly only focally in young. They become capable to generalize later with maturation, when the out-of-focus brain regions develop a decreased inhibitory/excitatory balance. These results suggest that a hyperexcitable focus is not sufficient alone to drive generalized absence seizures. Importantly, we also found the gradual age dependent disappearance of sleep spindles coinciding with the simultaneous gradual emergence of spike and waves, which both could be reversed by the proper dosing of ethosuximide (ETX). Based on these observations we conclude that the absence seizure development might be a multi-step process, which might involve the functional impairment of cortical interneurons and network-level changes that negatively affect sleep quality.</p>

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Proximodistal organization of the CA2 hippocampal area

2019, CELL REP 26:1-13

Fernandez-Lamo I, Gomez-Dominguez D, Sanchez-Aguilera A, Oliva A, Victoria Morales A, Valero M, Cid E, Berényi A, Menendez de la Prida L

<p>The proximodistal axis is considered a major organizational principle of the <a class='topic-link' title='Learn more about hippocampus from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/hippocampus'>hippocampus</a>. At the interface between the hippocampus and other <a class='topic-link' title='Learn more about brain from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/protocerebrum'>brain</a> structures, CA2 apparently breaks this rule. The region is involved in social, temporal, and contextual memory function, but mechanisms remain elusive. Here, we reveal cell-type heterogeneity and a characteristic expression gradient of the <a class='topic-link' title='Learn more about transcription factor Sox5 from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/immunology-and-microbiology/transcription-factor-sox5'>transcription factor Sox5</a> within CA2 in the rat. Using intracellular and extracellular recordings followed by neurochemical identification of single cells, we find marked proximodistal trends of synaptic activity, subthreshold membrane potentials, and phase-locked firing coupled to theta and gamma oscillations. Phase-shifting membrane potentials and opposite proximodistal correlations with theta sinks and sources at different layers support influences from different current generators. CA2 oscillatory activity and place coding of rats running in a linear maze reflect proximodistal state-dependent trends. We suggest that the structure and function of CA2 are distributed along the proximodistal hippocampal axis.</p>

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Immediate neurophysiological effects of transcranial electrical stimulation

2018, NAT COMM 9(1):5092

Liu A, Vöröslakos M, Kronberg G, Henin S, Krause MR, Huang Y, Opitz A, Mehta A, Pack CC, Krekelberg B, Berényi A, Parra LC, Melloni L, Devinsky O, Buzsáki G

<p>Noninvasive brain stimulation techniques are used in experimental and clinical fields for their potential effects on brain network dynamics and behavior. Transcranial electrical stimulation (TES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), has gained popularity because of its convenience and potential as a chronic therapy. However, a mechanistic understanding of TES has lagged behind its widespread adoption. Here, we review data and modelling on the immediate neurophysiological effects of TES in vitro as well as in vivo in both humans and other animals. While it remains unclear how typical TES protocols affect neural activity, we propose that validated models of current flow should inform study design and artifacts should be carefully excluded during signal recording and analysis. Potential indirect effects of TES (e.g., peripheral stimulation) should be investigated in more detail and further explored in experimental designs. We also consider how novel technologies may stimulate the next generation of TES experiments and devices, thus enhancing validity, specificity, and reproducibility.</p>

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Coding of self-motion induced and self-independent visual motion in the rat dorsomedial striatum

2018, PLOS BIOLOGY 16(6):e2004712

Anett Nagy, Yuichi Takeuchi, Antal Berényi

<p class='p1'>Evolutionary development of vision has provided us with the capacity to detect moving objects. Concordant shifts of visual features suggest movements of the observer, whereas discordant changes are more likely to be indicating independently moving objects, such as predators or prey. Such distinction helps us to focus attention, adapt our behavior, and adjust our motor patterns to meet behavioral challenges. However, the neural basis of distinguishing self-induced and self-independent visual motions is not clarified in unrestrained animals yet. In this study, we investigated the presence and origin of motion-related visual information in the striatum of rats, a hub of action selection and procedural memory. We found that while almost half of the neurons in the dorsomedial striatum are sensitive to visual motion congruent with locomotion (and that many of them also code for spatial location), only a small subset of them are composed of fast-firing interneurons that could also perceive self-independent visual stimuli. These latter cells receive their visual input at least partially from the secondary visual cortex (V2). This differential visual sensitivity may be an important support in adjusting behavior to salient environmental events. It emphasizes the importance of investigating visual motion perception in unrestrained animals.</p>

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Chronic transcranial electrical stimulation and intracortical recording in rats

2018, JOVE-J VIS EXP (135):e56669

Kozák G, Földi T, Berényi A

<p>Transcranial electrical stimulation (TES) is a powerful and relatively simple approach to diffusely influence brain activity either randomly or in a closed-loop event-triggered manner. Although many studies are focusing on the possible benefits and side-effects of TES in healthy and pathologic brains, there are still many fundamental open questions regarding the mechanism of action of the stimulation. Therefore, there is a clear need for a robust and reproducible method to test the acute and the chronic effects of TES in rodents. TES can be combined with regular behavioral, electrophysiological, and imaging techniques to investigate neuronal networks <em>in vivo</em>. The implantation of transcranial stimulation electrodes does not impose extra constraints on the experimental design while it offers a versatile, flexible tool to manipulate brain activity. Here we provide a detailed, step-by-step protocol to fabricate and implant transcranial stimulation electrodes to influence brain activity in a temporally constrained manner for months.</p>

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Direct effects of transcranial electric stimulation on brain circuits in rats and humans

2018, Nature Communication DOI: 10.1038/s41467-018-02928-3

Vöröslakos M, Takeuchi Y, Brinyiczki K, Zombori T, Oliva A, Fernández-Ruiz A, Kozák G, Kincses ZsT, Iványi B, Buzsáki G & Berényi A

<p>Transcranial electric stimulation is a non-invasive tool that can influence brain activity; however, the parameters necessary to affect local circuits in vivo remain to be explored. Here, we report that in rodents and human cadaver brains, ~75% of scalp-applied currents are attenuated by soft tissue and skull. Using intracellular and extracellular recordings in rats, we find that at least 1 mV/mm voltage gradient is necessary to affect neuronal spiking and subthreshold currents. We designed an ‘intersectional short pulse’ stimulation method to inject sufficiently high current intensities into the brain, while keeping the charge density and sensation on the scalp surface relatively low. We verify the regional specificity of this novel method in rodents; in humans, we demonstrate how it affects the amplitude of simultaneously<br />
recorded EEG alpha waves. Our combined results establish that neuronal circuits are instantaneously affected by intensity currents that are higher than those used in conventional protocols.</p>

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Entorhinal-CA3 dual-input control of spike timing in the hippocampus by theta-gamma coupling

2017, NEURON 93:1213-1226

Fernández-Ruiz A, Oliva A, Nagy GA, Maurer AP, Berényi A, Buzsáki G.

<p>Theta-gamma phase coupling and spike timing within theta oscillations are prominent features of the <a class='topic-link' title='Learn more about hippocampus from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/hippocampus'>hippocampus</a> and are often related to navigation and memory. However, the mechanisms that give rise to these relationships are not well understood. Using high spatial resolution <a class='topic-link' title='Learn more about electrophysiology from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/electrophysiology'>electrophysiology</a>, we investigated the influence of CA3 and entorhinal inputs on the timing of CA1 neurons. The theta-phase preference and excitatory strength of the afferent CA3 and entorhinal inputs effectively timed the principal neuron activity, as well as regulated distinct CA1 <a class='topic-link' title='Learn more about interneuron from ScienceDirect's AI-generated Topic Pages' href='https://www.sciencedirect.com/topics/neuroscience/interneuron'>interneuron</a> populations in multiple tasks and behavioral states. Feedback potentiation of distal dendritic inhibition by CA1 place cells attenuated the excitatory entorhinal input at place field entry, coupled with feedback depression of proximal dendritic and perisomatic inhibition, allowing the CA3 input to gain control toward the exit. Thus, upstream inputs interact with local mechanisms to determine theta-phase timing of hippocampal neurons to support memory and spatial navigation.</p>

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Incorporating single cell contribution into network models of ripple generation

2016, Journal of Physiology

Oliva A, Fernandez-Ruiz A

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Distributed representation of "what" and "where" information in the parahippocampal region

2016, Journal of Neuroscience. 36(32):8286-8288

Fernandez-Ruiz A, Oliva A

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Role of Hippocampal CA2 Region in Triggering Sharp-Wave Ripples

2016, Neuron in press

A Oliva, A Fernández-Ruiz, G Buzsáki, A Berényi

<p>Sharp-wave ripples (SPW-Rs) in the hippocampus are implied in memory consolidation, as shown by observational and interventional experiments. However, the mechanism of their generation remains unclear. Using two-dimensional silicon probe arrays, we investigated the propagation of SPW-Rs across the hippocampal CA1, CA2, and CA3 subregions. Synchronous activation of CA2 ensembles preceded SPW-R-related population activity in CA3 and CA1 regions. Deep CA2 neurons gradually increased their activity prior to ripples and were suppressed during the population bursts of CA3-CA1 neurons (ramping cells). Activity of superficial CA2 cells preceded the activity surge in CA3-CA1 (phasic cells). The trigger role of the CA2 region in SPW-R was more pronounced during waking than sleeping. These results point to the CA2 region as an initiation zone for SPW-Rs.</p>

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Neocortical gamma oscillations in idiopathic generalized epilepsy

2016, Epilepsia 57 (5), 796-804

K Benedek, A Berényi, P Gombkötő, H Piilgaard, M Lauritzen

<p>Absence seizures in patients with idiopathic generalized epilepsy (IGE) may in part be explained by a decrease in phasic GABAA (type-A γ-aminobutyric acid) receptor function, but the mechanisms are only partly understood. Here we studied the relation between ictal and interictal spike-wave discharges (SWDs) and electroencephalography (EEG) gamma oscillatory activity (30–60 Hz) in patients with IGE.</p>

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Tools for probing local circuits: high-density silicon probes combined with optogenetics

2015, Neuron 86(1):92-105.

Buzsáki G, Stark E, Berényi A, Khodagholy D, Kipke DR, Yoon E, Wise KD

<p>To understand how function arises from the interactions between neurons, it is necessary to use methods that allow the monitoring of brain activity at the single-neuron, single-spike level and the targeted manipulation of the diverse neuron types selectively in a closed-loop manner. Large-scale recordings of neuronal spiking combined with optogenetic perturbation of identified individual neurons has emerged as a suitable method for such tasks in behaving animals. To fully exploit the potential power of these methods, multiple steps of technical innovation are needed. We highlight the current state of the art in electrophysiological recording methods, combined with optogenetics, and discuss directions for progress. In addition, we point to areas where rapid development is in progress and discuss topics where near-term improvements are possible and needed.</p>

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Theta phase segregation of input-specific gamma patterns in entorhinal-hippocampal networks

2014, Neuron 84(2):470-85.

Schomburg EW, Fernández-Ruiz A, Mizuseki K, Berényi A, Anastassiou CA, Koch C, Buzsáki G

<p>Precisely how rhythms support neuronal communication remains obscure. We investigated interregional coordination of gamma oscillations using high-density electrophysiological recordings in the rat hippocampus and entorhinal cortex. We found that 30-80 Hz gamma dominated CA1 local field potentials (LFPs) on the descending phase of CA1 theta waves during navigation, with 60-120 Hz gamma at the theta peak. These signals corresponded to CA3 and entorhinal input, respectively. Above 50 Hz, interregional phase-synchronization of principal cell spikes occurred mostly for LFPs in the axonal target domain. CA1 pyramidal cells were phase-locked mainly to fast gamma (>100 Hz) LFP patterns restricted to CA1, which were strongest at the theta trough. While theta phase coordination of spiking across entorhinal-hippocampal regions depended on memory demands, LFP gamma patterns below 100 Hz in the hippocampus were consistently layer specific and largely reflected afferent activity. Gamma synchronization as a mechanism for interregional communication thus rapidly loses efficacy at higher frequencies.</p>

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Optogenetic activation of septal cholinergic neurons suppresses sharp wave ripples and enhances theta oscillations in the hippocampus

2014, Proc Natl Acad Sci U S A. 111(37):13535-40.

Vandecasteele M, Varga V, Berényi A, Papp E, Barthó P, Venance L, Freund TF, Buzsáki G

<p>Theta oscillations in the limbic system depend on the integrity of the medial septum. The different populations of medial septal neurons (cholinergic and GABAergic) are assumed to affect different aspects of theta oscillations. Using optogenetic stimulation of cholinergic neurons in ChAT-Cre mice, we investigated their effects on hippocampal local field potentials in both anesthetized and behaving mice. Cholinergic stimulation completely blocked sharp wave ripples and strongly suppressed the power of both slow oscillations (0.5– 2 Hz in anesthetized, 0.5–4 Hz in behaving animals) and supratheta (6–10 Hz in anesthetized, 10–25 Hz in behaving animals) bands. The same stimulation robustly increased both the power and coherence of theta oscillations (2–6 Hz) in urethane-anesthetized mice. In behaving mice, cholinergic stimulation was less effective in the theta (4–10 Hz) band yet it also increased the ratio of theta/slow oscillation and theta coherence. The effects on gamma oscillations largely mirrored those of theta. These findings show that medial septal cholinergic activation can both enhance theta rhythm and suppress peri-theta frequency bands, allowing theta oscillations to dominate.</p>

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Spatially distributed local fields in the hippocampus encode rat position

2014, Science 344(6184):626-30.

Agarwal G, Stevenson IH, Berényi A, Mizuseki K, Buzsáki G, Sommer FT

<p>Although neuronal spikes can be readily detected from extracellular recordings, synaptic and subthreshold activity remains undifferentiated within the local field potential (LFP). In the hippocampus, neurons discharge selectively when the rat is at certain locations, while LFPs at single anatomical sites exhibit no such place-tuning. Nonetheless, because the representation of position is sparse and distributed, we hypothesized that spatial information can be recovered from multiple-site LFP recordings. Using high-density sampling of LFP and computational methods, we show that the spatiotemporal structure of the theta rhythm can encode position as robustly as neuronal spiking populations. Because our approach exploits the rhythmicity and sparse structure of neural activity, features found in many brain regions, it is useful as a general tool for discovering distributed LFP codes.</p>

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Large-scale, high-density (up to 512 channels) recording of local circuits in behaving animals

2013, J Neurophysiol

A. Berényi, Z. Somogyvári, A. J. Nagy, L. Roux, J. Long, S. Fujisawa, E. Stark, A. Leonardo, T. D. Harris and G. Buzsáki

$<p style='text-align: justify;'>Monitoring representative fractions of neurons from multiple brain circuits in behaving animals is necessary for understanding neuronal computation. Here we describe a system that allows high channel count recordings from a small volume of neuronal tissue using a lightweight signal multiplexing head-stage that permits free behavior of small rodents. The system integrates multi-shank, high-density recording silicon probes, ultra-flexible interconnects and a miniaturized microdrive. These improvements allowed for simultaneous recordings of local field potentials and unit activity from hundreds of sites without confining free movements of the animal. The advantages of large-scale recordings are illustrated by determining the electro-anatomical boundaries of layers and regions in the hippocampus and neocortex and constructing a circuit diagram of functional connections among neurons in real anatomical space. These methods will allow the investigation of circuit operations and behavior-dependent inter-regional interactions for testing hypotheses of neural networks and brain function.</p>$

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Local generation and propagation of ripples along the septotemporal axis of the hippocampus

2013, J. Neurosci 33(43):17029 – 41

J. Patel, E. Schomburg, A. Berényi, S. Fujisawa, G. Buzsáki

<p style='text-align: justify;'>A topographical relationship exists between the septotemporal segments of the hippocampus and their entorhinal–neocortical targets, but the physiological organization of activity along the septotemporal axis is poorly understood.We recorded sharp-wave ripple patterns in rats during sleep from the entire septotemporal axis of the CA1 pyramidal layer. Qualitatively similar ripples emerged at all levels. From the local seed, ripples traveled septally or temporally at a speed of 0.35 m/s, and the spatial spread depended on ripple magnitude. Ripples propagated smoothly across the septal and intermediate segments of the hippocampus, but ripples in the temporal segment often remained isolated. These findings show that ripples can combine information from the septal and intermediate hippocampus and transfer integrated signals downstream. In contrast, ripples that emerged in the temporal pole broadcast largely independent information to their cortical and subcortical targets.</p>

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Traveling Theta Waves along the Entire Septotemporal Axis of the Hippocampus

2012, Neuron 75: 410-417

J. Patel, S. Fujisawa, A. Berényi, S. Royer, G. Buzsáki

<p style='text-align: justify;'>A topographical relationship exists between the hippocampus-entorhinal cortex and the neocortex. However, it is not known how these anatomical connections are utilized during information exchange and behavior. We recorded theta oscillations along the entire extent of the septotemporal axis of the hippocampal CA1 pyramidal layer. While the frequency of theta oscillation remained same along the entire long axis, the amplitude and coherence between recording sites decreased from dorsal to ventral hippocampus (VH). Theta phase shifted monotonically with distance along the longitudinal axis, reaching ∼180° between the septal and temporal poles. The majority of concurrently recorded units were phase-locked to the local field theta at all dorsoventral segments. The power of VH theta had only a weak correlation with locomotion velocity, and its amplitude varied largely independently from theta in the dorsal part. Thus, theta oscillations can temporally combine or segregate neocortical representations along the septotemporal axis of the hippocampus.</p>

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Closed-Loop Control of Epilepsy by Transcranial Electrical Stimulation

2012, Science 337: 735-737

A. Berényi, M. Belluscio, D. Mao, G. Buzsáki

<p><a href='http://science.sciencemag.org/content/344/6184/626.full.pdf+html '></a></p>

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A toolbox of Cre-dependent optogenetic transgenic mice for light-induced activation and silencing

2012, Nat Neurosci. 15: 793-802

L. Madisen, T. Mao, H. Koch, JM. Zhuo, A. Berényi, S. Fujisawa, YW. Hsu, AJ. Garcia 3rd, X. Gu, S. Zanella, J. Kidney, H. Gu, Y. Mao, BM. Hooks, ES. Boyden, G. Buzsáki, JM. Ramirez, AR. Jones, K. Svoboda, X. Han, EE. Turner, H. Zeng

<p style='text-align: justify;'>Cell type–specific expression of optogenetic molecules allows temporally precise manipulation of targeted neuronal activity. Here we present a toolbox of four knock-in mouse lines engineered for strong, Cre-dependent expression of channelrhodopsins ChR2-tdTomato and ChR2-EYFP, halorhodopsin eNpHR3.0 and archaerhodopsin Arch-ER2. All four transgenes mediated Cre-dependent, robust activation or silencing of cortical pyramidal neurons in vitro and in vivo upon light stimulation, with ChR2-EYFP and Arch-ER2 demonstrating light sensitivity approaching that of in utero or virally transduced neurons. We further show specific photoactivation of parvalbumin-positive interneurons in behaving ChR2-EYFP reporter mice. The robust, consistent and inducible nature of our ChR2 mice represents a significant advance over previous lines, and the Arch-ER2 and eNpHR3.0 mice are to our knowledge the first demonstration of successful conditional transgenic optogenetic silencing. When combined with the hundreds of available Cre driver lines, this optimized toolbox of reporter mice will enable widespread investigations of neural circuit function with unprecedented reliability and accuracy.</p>

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Large-scale Recording of Neurons by Movable Silicon Probes in Behaving Rodents

2012, J Vis Exp. 61: e3568. doi: 10.3791/3568

M. Vandecasteele, S. Royer, M. Belluscio, A. Berényi, K. Diba, S. Fujisawa, A. Grosmark, D. Mao, K. Mizuseki, J. Patel, E. Stark, D. Sullivan, B. Watson, G. Buzsáki

<p style='text-align: justify;'>A major challenge in neuroscience is linking behavior to the collective activity of neural assemblies. Understanding of input-output relationships of neurons and circuits requires methods with the spatial selectivity and temporal resolution appropriate for mechanistic analysis of neural ensembles in the behaving animal, i.e. recording of representatively large samples of isolated single neurons. Ensemble monitoring of neuronal activity has progressed remarkably in the past decade in both small and large-brained animals, including human subjects1-11. Multiple-site recording with silicon-based devices are particularly effective because of their scalability, small volume and geometric design.</p>
<p>Here, we describe methods for recording multiple single neurons and local field potential in behaving rodents, using commercially available micro-machined silicon probes with custom-made accessory components. There are two basic options for interfacing silicon probes to preamplifiers: printed circuit boards and flexible cables. Probe supplying companies (http://www.neuronexustech.com/; http://www.sbmicrosystems.com/; http://www.acreo.se/) usually provide the bonding service and deliver probes bonded to printed circuit boards or flexible cables. Here, we describe the implantation of a 4-shank, 32-site probe attached to flexible polyimide cable, and mounted on a movable microdrive. Each step of the probe preparation, microdrive construction and surgery is illustrated so that the end user can easily replicate the process.</p>

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Direct projection from the visual associative cortex to the caudate nucleus in the feline brain

2011, Neurosci Lett 503: 52-57

AJ. Nagy, A. Berényi, K. Gulya, M. Norita, G. Benedek, A. Nagy

<p style='text-align: justify;'>Recent morphological and physiological studies support the assumption that the extrageniculate ascending tectofugal pathways send visual projection to the caudate nucleus (CN) in amniotes. In the present study we investigate the anatomical connection between the visual associative cortex along the anterior ectosylvian sulcus (AES) and the CN in adult domestic cats. An anterograde tracer – fluoro-dextrane-amine – was injected into the AES cortex. The distribution of labeled axons was not uniform in the CN. The majority of labeled axons and terminal like puncta was found only in a limited area in the dorsal part of the CN between the coordinates anterior 12–15. Furthermore, a retrograde tracer – choleratoxin-B – was injected into the dorsal part of the CN between anterior 12 and 13. We detected a large number of labeled neurons in the fundus and the dorsal part of the AES between the coordinates anterior 12–14. Based upon our recent results we argue that there is a direct monosynaptic connection between the visual associative cortex along the AES and the CN. Beside the posterior thalamus, the AES cortex should also participate in the transmission of the tectal visual information to the CN. This pathway is likely to convey complex information containing both sensory and motor components toward the basal ganglia, which supports their integrative function in visuomotor actions such as motion and novelty detection and saccade generation.</p>

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Spectral receptive field properties of visually active neurons in the caudate nucleus

2010, Neurosci Lett 480: 148-153

A. Nagy, A. Berényi, M. Wypych, WJ. Waleszczyk, G. Benedek

<p style='text-align: justify;'>Recent studies stress the importance of the caudate nucleus in visual information processing. Although the processing of moving visual signals depends upon the capability of a system to integrate spatial and temporal information, no study has investigated the spectral receptive field organization of the caudate nucleus neurons yet. Therefore, we tested caudate neurons of the feline brain by extracellular single-cell recording applying drifting sinewave gratings of various spatial and temporal frequencies, and reconstructed their spectral receptive fields by plotting their responsiveness as a function of different combinations of spatial and temporal frequencies. The majority of the caudate cells (74%) exhibited peak tuning, which means that their spatio-temporal frequency response profile had a characteristic region of increased activity with a single maximum in the spatio-temporal frequency domain. In one-quarter of the recorded caudate neurons ridge tuning was found, where the region of increased activity, forming an elongated ridge of maximal sensitivity parallel or angled to the spatial or the temporal frequency axis, indicating temporal (16%), spatial (5%) or speed (5%) tuning, respectively. The velocity preference of the ridge tuned caudate nucleus neurons is significantly lower than that of the peak tuned neurons. The peak tuned neuron could encode high velocities, while the ridge tuned neurons were responsible for the detection of moderate and lower velocities. Based upon our results, we suggest that the wide variety of spatio-temporal frequency response profiles might represent different functional neuronal groups within the caudate nucleus that subserve different behaviors to meet various environmental requirements.</p>

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Direct synaptic connections between superior colliculus afferents and thalamo-insular projection neurons in the feline suprageniculate nucleus

2009, Neurosci Res. 66: 7-13

K. Hoshino, M. Horie, A. Nagy, A. Berényi, G. Benedek, M. Norita

<p style='text-align: justify;'>The suprageniculate nucleus (Sg) of the feline thalamus, which subserves largely unimodal sensory and orientation behavior, receives input from the deep layers of the superior colliculus (SC), and projects to the suprasylvian cortical areas, such as the anterior ectosylvian visual area and the insular visual area (IVA), which contain visually responsive neurons. Through a double tract-tracing procedure involving the injection of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) into the IVA and the injection of kainic acid into the SC, this study sought to determine the nature of the synaptic relationship between the SC afferents and the thalamo-cortical projection neurons. WGA-HRP injections labeled numerous neurons in the Sg, while kainic acid injections destroyed many tectothalamic terminals in the Sg. The distributions of the WGA-HRP-labeled neurons and the degenerated axon terminals overlapped in the dorsal part of the Sg. Electron microscopic observations demonstrated that the degenerated axon terminals made synaptic contacts with the dendrites of the WGA-HRP-labeled neurons in this overlapping region of the Sg. These results provide the first anatomical evidence that the Sg may play a role in the key relay of visual information from the SC to the IVA, within an identified extrageniculo-cortical pathway.</p>

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How moving visual stimuli modulate the activity of the substantia nigra pars reticulata

2009, Neuroscience 163 (4), 1316-1326.

A Berényi, P Gombkötő, Á Farkas, Z Paróczy, Z Márkus, RG Averkin, G Benedek, A Nagy

<p style='text-align: justify;'>The orientation of spatial attention via saccades is modulated by a pathway from the substantia nigra pars reticularis (SNr) to the superior colliculus, which enhances the ability to respond to novel stimuli. However, the algorithm whereby the SNr translates visual input to saccade-related information is still unknown. We recorded extracellular single-unit responses of 343 SNr cells to visual stimuli in anesthetized cats. Depending on the size, velocity and direction of the visual stimulus, SNr neurons responded by either increasing or decreasing their firing rate. Using artificial neuronal networks, visual SNr neurons could be classified into distinct groups. Some of the units showed a clear preference for one specific combination of direction and velocity (simple neurons), while other SNr neurons were sensitive to the direction (direction-tuned neurons) or the velocity (velocitytuned neurons) of the movement. Furthermore, a subset of SNr neurons exhibited a narrow inhibitory/excitatory domain in the velocity/direction plane with an opposing surround (concentric neurons). According to our results, spatiotemporally represented visual information may determine the discharge pattern of the SNr. We suggest that the SNr utilizes spatiotemporal properties of the visual information to generate vector-based commands, which could modulate the activity of the superior colliculus and enhance or inhibit the reflexive initiation of complex and accurate saccades.</p>

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Spatial and temporal visual properties of the neurons in the intermediate layers of the superior colliculus

2009, Neurosci Lett 454: 76-80

Z. Márkus, A. Berényi, Z. Paróczy, M. Wypych, WJ. Waleszczyk, G. Benedek, A. Nagy

<p style='text-align: justify;'>Although the visual perception depends on the integration of spatial and temporal information, no knowledge is available concerning the responsiveness of neurons in the intermediate layers of the superior colliculus (SCi) to extended visual grating stimuli. Accordingly, we set out to investigate the responsiveness of these neurons in halothane-anesthetized cats to drifting sinewave gratings at various spatial and temporal frequencies. The SCi units responded optimally to gratings of low spatial frequencies (none of the analyzed SCi units exhibited maximal activity to spatial frequencies higher than 0.3 c/deg) and exhibited low spatial resolution and narrow spatial frequency tuning. On the other hand, the SCi neurons preferred high temporal frequencies and exhibited high temporal resolution. Thus, the SCi neurons seem to be good spatio–temporal filters of visual information in the low spatial and high temporal frequency domain. Based upon the above summarized results we suggest that the SCi units can detect large contours moving at high velocities well, but are unable to distinguish small details. This is in line with the generally held view that the SCi could possess visuomotor function, such as organizing the complex, sensory-guided oculomotor and skeletomotor responses during the self-motion of the animal.</p>

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Drifting grating stimulation reveals particular activation properties of visual neurons in the caudate nucleus

2008, Eur J Neurosci 27: 1801-1808

A. Nagy, Z. Paróczy, Z. Márkus, A. Berényi, M. Wypych, WJ. Waleszczyk, G. Benedek

<p style='text-align: justify;'>The role of the caudate nucleus (CN) in motor control has been widely studied. Less attention has been paid to the dynamics of visual feedback in motor actions, which is a relevant function of the basal ganglia during the control of eye and body movements. We therefore set out to analyse the visual information processing of neurons in the feline CN. Extracellular single-unit recordings were performed in the CN, where the neuronal responses to drifting gratings of various spatial and temporal frequencies were recorded. The responses of the CN neurons were modulated by the temporal frequency of the grating. The CN units responded optimally to gratings of low spatial frequencies and exhibited low spatial resolution and fine spatial frequency tuning. By contrast, the CN neurons preferred high temporal frequencies, and exhibited high temporal resolution and fine temporal frequency tuning. The spatial and temporal visual properties of the CN neurons enable them to act as spatiotemporal filters. These properties are similar to those observed in certain feline extrageniculate visual structures, i.e. in the superior colliculus, the suprageniculate nucleus and the anterior ectosylvian cortex, but differ strongly from those of the primary visual cortex and the lateral geniculate nucleus. Accordingly, our results suggest a functional relationship of the CN to the extrageniculate tecto-thalamo-cortical system. This system of the mammalian brain may be involved in motion detection, especially in velocity analysis of moving objects, facilitating the detection of changes during the animal’s movement.</p>

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Double sliding-window technique: a new method to calculate the neuronal response onset latency

2007, Brain Res 1178: 141-148

A. Berenyi, G. Benedek, A. Nagy

<p style='text-align: justify;'>Neuronal response onset latency provides important data on the information processing within the central nervous system. In order to enhance the quality of the onset latency estimation, we have developed a ‘double sliding-window’ technique, which combines the advantages of mathematical methods with the reliability of standard statistical processes. This method is based on repetitive series of statistical probes between two virtual time windows. The layout of the significance curve reveals the starting points of changes in neuronal activity in the form of break-points between linear segments. A second-order difference function is applied to determine the position of maximum slope change, which corresponds to the onset of the response. In comparison with Poisson spike-train analysis, the cumulative sum technique and the method of Falzett et al., this ‘double sliding-window, technique seems to be a more accurate automated procedure to calculate the response onset latency of a broad range of neuronal response characteristics.</p>

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Spectral receptive field properties of neurons in the feline superior colliculus

2007, Exp Brain Res 181: 87-98

Waleszczyk WJ., A. Nagy, M. Wypych, A. Berényi, Z. Paróczy, G. Eördegh, A. Ghazaryan, G. Benedek

<p style='text-align: justify;'>The spatio-temporal frequency response profiles of 73 neurons located in the superWcial, retino-recipient layers of the feline superior colliculus (SC) were investigated. The majority of the SC cells responded optimally to very low spatial frequencies with a mean of 0.1 cycles/degree (c/deg). The spatial resolution was also low with a mean of 0.31 c/deg. The spatial frequency tuning functions were either low-pass or band-pass with a mean spatial frequency bandwidth of 1.84 octaves. The cells responded optimally to a range of temporal frequencies between 0.74 cycles/s (c/s) and 26.41 c/s with a mean of 6.84 c/s. The majority (68%) of the SC cells showed band-pass temporal frequency tuning with a mean temporal frequency bandwidth of 2.4 octaves, while smaller proportions of the SC units displayed high-pass (19%), low-pass (8%) or broad-band (5%) temporal tuning. Most of the SC units exhibited simple spectral tuning with a single maximum in the spatio-temporal frequency domain, while some neurons were tuned for spatial or temporal frequencies or speed tuned. Further, we found cells excited by gratings moving at high temporal and low spatial frequencies and cells whose activity was suppressed by high velocity movement. The spatio-temporal fillter properties of the SC neurons show close similarities to those of their retinal Y and W inputs as well as those of their inputs from the cortical visual motion detector areas, suggesting their common role in motion analysis and related behavioral actions.</p>

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Processing of spatial visual information along the pathway between the suprageniculate nucleus and the anterior ectosylvian cortex

2005, Brain Res Bull 67: 281-289

G. Eördegh, A. Nagy, A. Berényi, G. Benedek

<p style='text-align: justify;'>This study describes the visual information coding ability of single neurons in the suprageniculate nucleus (Sg), and provides new data concerning the visual information flow in the suprageniculate/anterior ectosylvian pathways of the feline brain. The visual receptive fields of the Sg neurons have an internal structure rather similar to that described earlier in the anterior ectosylvian visual area (AEV). The majority of the Sg units can provide information via their discharge rate at the site of the visual stimulus within their large receptive fields. This suggests that they may serve as panoramic localizers. The sites of maximum responsivity of the Sg neurons are distributed over the whole investigated part of the visual field. There is no significant difference between the distributions of spatial location of maximum sensitivity of the AEV and the Sg neurons. The mean visual response latency of the Sg units was found to be significantly shorter than the mean latency of the AEV neurons, but there was no difference between the shortest latency values of the thalamic and the cortical single-units. This suggests that the visual information flows predominantly from the Sg to the AEV, though the cortico-thalamic route is also active. The Sg seems to represent a thalamic nucleus rather similar in function to both the first-order relays and the higher-order thalamic nuclei. These results, together with the fact that the superior colliculus provides the common ascending source of information to the suprageniculate/anterior ectosylvian pathway, suggest a unique function of the AEV and the Sg in sensorimotor integration.</p>

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