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Shore AN, Li K, Safari M, Qunies AM, Spitznagel BD, Weaver CD, Emmitte K, Frankel W, Weston MC. Heterozygous expression of a Kcnt1 gain-of-function variant has differential effects on SST- and PV-expressing cortical GABAergic neurons. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.11.561953. [PMID: 37873369 PMCID: PMC10592778 DOI: 10.1101/2023.10.11.561953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
More than twenty recurrent missense gain-of-function (GOF) mutations have been identified in the sodium-activated potassium (K Na ) channel gene KCNT1 in patients with severe developmental and epileptic encephalopathies (DEEs), most of which are resistant to current therapies. Defining the neuron types most vulnerable to KCNT1 GOF will advance our understanding of disease mechanisms and provide refined targets for precision therapy efforts. Here, we assessed the effects of heterozygous expression of a Kcnt1 GOF variant (Y777H) on K Na currents and neuronal physiology among cortical glutamatergic and GABAergic neurons in mice, including those expressing vasoactive intestinal polypeptide (VIP), somatostatin (SST), and parvalbumin (PV), to identify and model the pathogenic mechanisms of autosomal dominant KCNT1 GOF variants in DEEs. Although the Kcnt1 -Y777H variant had no effects on glutamatergic or VIP neuron function, it increased subthreshold K Na currents in both SST and PV neurons but with opposite effects on neuronal output; SST neurons became hypoexcitable with a higher rheobase current and lower action potential (AP) firing frequency, whereas PV neurons became hyperexcitable with a lower rheobase current and higher AP firing frequency. Further neurophysiological and computational modeling experiments showed that the differential effects of the Y777H variant on SST and PV neurons are not likely due to inherent differences in these neuron types, but to an increased persistent sodium current in PV, but not SST, neurons. The Y777H variant also increased excitatory input onto, and chemical and electrical synaptic connectivity between, SST neurons. Together, these data suggest differential pathogenic mechanisms, both direct and compensatory, contribute to disease phenotypes, and provide a salient example of how a pathogenic ion channel variant can cause opposite functional effects in closely related neuron subtypes due to interactions with other ionic conductances.
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Potter C, Bassi C, Runyan CA. Simultaneous interneuron labeling reveals population-level interactions among parvalbumin, somatostatin, and pyramidal neurons in cortex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.01.09.523298. [PMID: 36711788 PMCID: PMC9882008 DOI: 10.1101/2023.01.09.523298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Cortical interneurons shape network activity in cell type-specific ways, and are also influenced by interactions with other cell types. These specific cell-type interactions are understudied, as transgenic labeling methods typically restrict labeling to one neuron type at a time. Although recent methods have enabled post-hoc identification of cell types, these are not available to many labs. Here, we present a method to distinguish between two red fluorophores in vivo, which allowed imaging of activity in somatostatin (SOM), parvalbumin (PV), and putative pyramidal neurons (PYR) in mouse association cortex. We compared population events of elevated activity and observed that the PYR network state corresponded to the ratio between mean SOM and PV neuron activity, demonstrating the importance of simultaneous labeling to explain dynamics. These results extend previous findings in sensory cortex, as activity became sparser and less correlated when the ratio between SOM and PV activity was high.
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Affiliation(s)
- Christian Potter
- Department of Neuroscience
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA
| | - Constanza Bassi
- Department of Neuroscience
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA
| | - Caroline A. Runyan
- Department of Neuroscience
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA
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3
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Aussel A, Fiebelkorn IC, Kastner S, Kopell NJ, Pittman-Polletta BR. Interacting rhythms enhance sensitivity of target detection in a fronto-parietal computational model of visual attention. eLife 2023; 12:e67684. [PMID: 36718998 PMCID: PMC10129332 DOI: 10.7554/elife.67684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 01/12/2023] [Indexed: 02/01/2023] Open
Abstract
Even during sustained attention, enhanced processing of attended stimuli waxes and wanes rhythmically, with periods of enhanced and relatively diminished visual processing (and subsequent target detection) alternating at 4 or 8 Hz in a sustained visual attention task. These alternating attentional states occur alongside alternating dynamical states, in which lateral intraparietal cortex (LIP), the frontal eye field (FEF), and the mediodorsal pulvinar (mdPul) exhibit different activity and functional connectivity at α, β, and γ frequencies-rhythms associated with visual processing, working memory, and motor suppression. To assess whether and how these multiple interacting rhythms contribute to periodicity in attention, we propose a detailed computational model of FEF and LIP. When driven by θ-rhythmic inputs simulating experimentally-observed mdPul activity, this model reproduced the rhythmic dynamics and behavioral consequences of observed attentional states, revealing that the frequencies and mechanisms of the observed rhythms allow for peak sensitivity in visual target detection while maintaining functional flexibility.
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Affiliation(s)
- Amélie Aussel
- Cognitive Rhythms Collaborative, Boston UniversityBostonUnited States
- Department of Mathematics and Statistics, Boston UniversityRochesterUnited States
| | - Ian C Fiebelkorn
- Department of Neuroscience and Del Monte Institute for Neuroscience, University of Rochester Medical Center, University of RochesterRochesterUnited States
- Princeton Neuroscience Institute, Princeton UniversityPrincetonUnited States
| | - Sabine Kastner
- Princeton Neuroscience Institute, Princeton UniversityPrincetonUnited States
- Department of Psychology, Princeton UniversityPrincetonUnited States
| | - Nancy J Kopell
- Cognitive Rhythms Collaborative, Boston UniversityBostonUnited States
- Department of Mathematics and Statistics, Boston UniversityRochesterUnited States
| | - Benjamin Rafael Pittman-Polletta
- Cognitive Rhythms Collaborative, Boston UniversityBostonUnited States
- Department of Mathematics and Statistics, Boston UniversityRochesterUnited States
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4
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Vaughn MJ, Haas JS. On the Diverse Functions of Electrical Synapses. Front Cell Neurosci 2022; 16:910015. [PMID: 35755782 PMCID: PMC9219736 DOI: 10.3389/fncel.2022.910015] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/25/2022] [Indexed: 11/13/2022] Open
Abstract
Electrical synapses are the neurophysiological product of gap junctional pores between neurons that allow bidirectional flow of current between neurons. They are expressed throughout the mammalian nervous system, including cortex, hippocampus, thalamus, retina, cerebellum, and inferior olive. Classically, the function of electrical synapses has been associated with synchrony, logically following that continuous conductance provided by gap junctions facilitates the reduction of voltage differences between coupled neurons. Indeed, electrical synapses promote synchrony at many anatomical and frequency ranges across the brain. However, a growing body of literature shows there is greater complexity to the computational function of electrical synapses. The paired membranes that embed electrical synapses act as low-pass filters, and as such, electrical synapses can preferentially transfer spike after hyperpolarizations, effectively providing spike-dependent inhibition. Other functions include driving asynchronous firing, improving signal to noise ratio, aiding in discrimination of dissimilar inputs, or dampening signals by shunting current. The diverse ways by which electrical synapses contribute to neuronal integration merits furthers study. Here we review how functions of electrical synapses vary across circuits and brain regions and depend critically on the context of the neurons and brain circuits involved. Computational modeling of electrical synapses embedded in multi-cellular models and experiments utilizing optical control and measurement of cellular activity will be essential in determining the specific roles performed by electrical synapses in varying contexts.
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Affiliation(s)
- Mitchell J Vaughn
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
| | - Julie S Haas
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
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5
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Cummings KA, Lacagnina AF, Clem RL. GABAergic microcircuitry of fear memory encoding. Neurobiol Learn Mem 2021; 184:107504. [PMID: 34425220 DOI: 10.1016/j.nlm.2021.107504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 08/12/2021] [Accepted: 08/15/2021] [Indexed: 12/30/2022]
Abstract
The paradigm of fear conditioning is largely responsible for our current understanding of how memories are encoded at the cellular level. Its most fundamental underlying mechanism is considered to be plasticity of synaptic connections between excitatory projection neurons (PNs). However, recent studies suggest that while PNs execute critical memory functions, their activity at key stages of learning and recall is extensively orchestrated by a diverse array of GABAergic interneurons (INs). Here we review the contributions of genetically-defined INs to processing of threat-related stimuli in fear conditioning, with a particular focus on how synaptic interactions within interconnected networks of INs modulates PN activity through both inhibition and disinhibition. Furthermore, we discuss accumulating evidence that GABAergic microcircuits are an important locus for synaptic plasticity during fear learning and therefore a viable substrate for long-term memory. These findings suggest that further investigation of INs could unlock unique conceptual insights into the organization and function of fear memory networks.
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Affiliation(s)
- Kirstie A Cummings
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States; Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States; Department of Neurobiology, University of Alabama Birmingham School of Medicine, Birmingham, AL 35294, United States
| | - Anthony F Lacagnina
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States; Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Roger L Clem
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States; Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States.
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6
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Huang P, Xiang X, Chen X, Li H. Somatostatin Neurons Govern Theta Oscillations Induced by Salient Visual Signals. Cell Rep 2020; 33:108415. [PMID: 33238116 DOI: 10.1016/j.celrep.2020.108415] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 09/14/2020] [Accepted: 10/29/2020] [Indexed: 01/21/2023] Open
Abstract
Salient visual stimuli enhance theta oscillations and spike-phase locking in the theta band in the primary visual cortex (V1) of mice; however, the detailed mechanisms remain unknown. GABAergic neurons play a vital role in regulating these oscillations. Here, we use optogenetic recordings to tag cell-type-specific neurons in V1 of head-fixed mice and demonstrate that salient visual stimuli facilitate somatostatin (SOM)-expressing neuron responses and firing with theta band oscillations but suppress activities of parvalbumin (PV)-expressing neurons. Furthermore, inactivation of SOM neurons attenuates the enhancement of theta oscillations induced by salient visual stimuli and rhythmic activation of SOM neurons enhances theta oscillations. These results reveal a potential cortical theta oscillation mechanism governed by SOM neurons.
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Affiliation(s)
- Pengcheng Huang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; MoE Key Laboratory for Biomedical Photonics, Collaborative Innovation Center for Biomedical Engineering, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Xinkuan Xiang
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; MoE Key Laboratory for Biomedical Photonics, Collaborative Innovation Center for Biomedical Engineering, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Xinfeng Chen
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; MoE Key Laboratory for Biomedical Photonics, Collaborative Innovation Center for Biomedical Engineering, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Haohong Li
- Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; MoE Key Laboratory for Biomedical Photonics, Collaborative Innovation Center for Biomedical Engineering, School of Engineering Sciences, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.
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CaMKIIα-Positive Interneurons Identified via a microRNA-Based Viral Gene Targeting Strategy. J Neurosci 2020; 40:9576-9588. [PMID: 33158963 DOI: 10.1523/jneurosci.2570-19.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 01/08/2023] Open
Abstract
Single-cell analysis is revealing increasing diversity in gene expression profiles among brain cells. Traditional promotor-based viral gene expression techniques, however, cannot capture the growing variety among single cells. We demonstrate a novel viral gene expression strategy to target cells with specific miRNA expression using miRNA-guided neuron tags (mAGNET). We designed mAGNET viral vectors containing a CaMKIIα promoter and microRNA-128 (miR-128) binding sites, and labeled CaMKIIα+ cells with naturally low expression of miR-128 (Lm128C cells) in male and female mice. Although CaMKIIα has traditionally been considered as an excitatory neuron marker, our single-cell sequencing results reveal that Lm128C cells are CaMKIIα+ inhibitory neurons of parvalbumin or somatostatin subtypes. Further evaluation of the physiological properties of Lm128C cell in brain slices showed that Lm128C cells exhibit elevated membrane excitability, with biophysical properties closely resembling those of fast-spiking interneurons, consistent with previous transcriptomic findings of miR-128 in regulating gene networks that govern membrane excitability. To further demonstrate the utility of this new viral expression strategy, we expressed GCaMP6f in Lm128C cells in the superficial layers of the motor cortex and performed in vivo calcium imaging in mice during locomotion. We found that Lm128C cells exhibit elevated calcium event rates and greater intrapopulation correlation than the overall CaMKIIα+ cells during movement. In summary, the miRNA-based viral gene targeting strategy described here allows us to label a sparse population of CaMKIIα+ interneurons for functional studies, providing new capabilities to investigate the relationship between gene expression and physiological properties in the brain.SIGNIFICANCE STATEMENT We report the discovery of a class of CaMKIIα+ cortical interneurons, labeled via a novel miRNA-based viral gene targeting strategy, combinatorial to traditional promoter-based strategies. The fact that we found a small, yet distinct, population of cortical inhibitory neurons that express CaMKIIα demonstrates that CaMKIIα is not as specific for excitatory neurons as commonly believed. As single-cell sequencing tools are providing increasing insights into the gene expression diversity of neurons, including miRNA profile data, we expect that the miRNA-based gene targeting strategy presented here can help delineate many neuron populations whose physiological properties can be readily related to the miRNA gene regulatory networks.
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8
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Hoehne A, McFadden MH, DiGregorio DA. Feed-forward recruitment of electrical synapses enhances synchronous spiking in the mouse cerebellar cortex. eLife 2020; 9:57344. [PMID: 32990593 PMCID: PMC7524550 DOI: 10.7554/elife.57344] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Accepted: 09/09/2020] [Indexed: 01/21/2023] Open
Abstract
In the cerebellar cortex, molecular layer interneurons use chemical and electrical synapses to form subnetworks that fine-tune the spiking output of the cerebellum. Although electrical synapses can entrain activity within neuronal assemblies, their role in feed-forward circuits is less well explored. By combining whole-cell patch-clamp and 2-photon laser scanning microscopy of basket cells (BCs), we found that classical excitatory postsynaptic currents (EPSCs) are followed by GABAA receptor-independent outward currents, reflecting the hyperpolarization component of spikelets (a synapse-evoked action potential passively propagating from electrically coupled neighbors). FF recruitment of the spikelet-mediated inhibition curtails the integration time window of concomitant excitatory postsynaptic potentials (EPSPs) and dampens their temporal integration. In contrast with GABAergic-mediated feed-forward inhibition, the depolarizing component of spikelets transiently increases the peak amplitude of EPSPs, and thus postsynaptic spiking probability. Therefore, spikelet transmission can propagate within the BC network to generate synchronous inhibition of Purkinje cells, which can entrain cerebellar output for driving temporally precise behaviors.
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Affiliation(s)
- Andreas Hoehne
- Laboratory of Synapse and Circuit Dynamics, Institut Pasteur, Paris Cedex, France.,Sorbonne University, ED3C, Paris, France
| | - Maureen H McFadden
- Laboratory of Synapse and Circuit Dynamics, Institut Pasteur, Paris Cedex, France
| | - David A DiGregorio
- Laboratory of Synapse and Circuit Dynamics, Institut Pasteur, Paris Cedex, France
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9
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Kawaguchi Y, Otsuka T, Morishima M, Ushimaru M, Kubota Y. Control of excitatory hierarchical circuits by parvalbumin-FS basket cells in layer 5 of the frontal cortex: insights for cortical oscillations. J Neurophysiol 2019; 121:2222-2236. [PMID: 30995139 PMCID: PMC6620693 DOI: 10.1152/jn.00778.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cortex contains multiple neuron types with specific connectivity and functions. Recent progress has provided a better understanding of the interactions of these neuron types as well as their output organization particularly for the frontal cortex, with implications for the circuit mechanisms underlying cortical oscillations that have cognitive functions. Layer 5 pyramidal cells (PCs) in the frontal cortex comprise two major subtypes: crossed-corticostriatal (CCS) and corticopontine (CPn) cells. Functionally, CCS and CPn cells exhibit similar phase-dependent firing during gamma waves but participate in two distinct subnetworks that are linked unidirectionally from CCS to CPn cells. GABAergic parvalbumin-expressing fast-spiking (PV-FS) cells, necessary for gamma oscillation, innervate PCs, with stronger and global inhibition to somata and weaker and localized inhibitions to dendritic shafts/spines. While PV-FS cells form reciprocal connections with both CCS and CPn cells, the excitation from CPn to PV-FS cells exhibits short-term synaptic dynamics conducive for oscillation induction. The electrical coupling between PV-FS cells facilitates spike synchronization among PV-FS cells receiving common excitatory inputs from local PCs and inhibits other PV-FS cells via electrically communicated spike afterhyperpolarizations. These connectivity characteristics can promote synchronous firing in the local networks of CPn cells and firing of some CCS cells by anode-break excitation. Thus subsets of L5 CCS and CPn cells within different levels of connection hierarchy exhibit coordinated activity via their common connections with PV-FS cells, and the resulting PC output drives diverse neuronal targets in cortical layer 1 and the striatum with specific temporal precision, expanding the computational power of the cortical network.
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Affiliation(s)
- Yasuo Kawaguchi
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
| | - Takeshi Otsuka
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
| | - Mieko Morishima
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
| | - Mika Ushimaru
- Department of Experimental Therapeutics, Institute for Advancement of Clinical and Translational Science, Kyoto University Hospital , Kyoto , Japan
| | - Yoshiyuki Kubota
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
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10
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Morishima M, Kobayashi K, Kato S, Kobayashi K, Kawaguchi Y. Segregated Excitatory-Inhibitory Recurrent Subnetworks in Layer 5 of the Rat Frontal Cortex. Cereb Cortex 2018; 27:5846-5857. [PMID: 29045559 PMCID: PMC5905586 DOI: 10.1093/cercor/bhx276] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
A prominent feature of neocortical pyramidal cells (PCs) is their numerous projections to diverse brain areas. In layer 5 (L5) of the rat frontal cortex, there are 2 major subtypes of PCs that differ in their long-range axonal projections, corticopontine (CPn) cells and crossed corticostriatal (CCS) cells. The outputs of these L5 PCs can be regulated by feedback inhibition from neighboring cortical GABAergic cells. Two major subtypes of GABAergic cells are parvalbumin (PV)-positive and somatostatin (SOM)-positive cells. PV cells have a fast-spiking (FS) firing pattern, while SOM cells have a low threshold spike (LTS) and regular spiking. In this study, we found that the 2 PC subtypes in L5 selectively make recurrent connections with LTS cells. The connection patterns correlated with the morphological and physiological diversity of LTS cells. LTS cells with high input resistance (Ri) exhibited more compact dendrites and more rebound spikes than LTS cells with low Ri, which had vertically elongated dendrites. LTS subgroups differently inhibited the PC subtypes, although FS cells made nonselective connections with both projection subtypes. These results demonstrate a novel recurrent network of inhibitory and projection-specific excitatory neurons within the neocortex.
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Affiliation(s)
- Mieko Morishima
- Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), Okazaki 444-8787, Japan
| | - Kenta Kobayashi
- Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), Okazaki 444-8787, Japan.,Section of Viral Vector Development, Center for Genetic Analysis of Behavior, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Shigeki Kato
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University, Fukushima 960-1295, Japan
| | - Kazuto Kobayashi
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University, Fukushima 960-1295, Japan
| | - Yasuo Kawaguchi
- Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8787, Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), Okazaki 444-8787, Japan
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Hakim R, Shamardani K, Adesnik H. A neural circuit for gamma-band coherence across the retinotopic map in mouse visual cortex. eLife 2018; 7:28569. [PMID: 29480803 PMCID: PMC5826269 DOI: 10.7554/elife.28569] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 02/15/2018] [Indexed: 11/13/2022] Open
Abstract
Cortical gamma oscillations have been implicated in a variety of cognitive, behavioral, and circuit-level phenomena. However, the circuit mechanisms of gamma-band generation and synchronization across cortical space remain uncertain. Using optogenetic patterned illumination in acute brain slices of mouse visual cortex, we define a circuit composed of layer 2/3 (L2/3) pyramidal cells and somatostatin (SOM) interneurons that phase-locks ensembles across the retinotopic map. The network oscillations generated here emerge from non-periodic stimuli, and are stimulus size-dependent, coherent across cortical space, narrow band (30 Hz), and depend on SOM neuron but not parvalbumin (PV) neuron activity; similar to visually induced gamma oscillations observed in vivo. Gamma oscillations generated in separate cortical locations exhibited high coherence as far apart as 850 μm, and lateral gamma entrainment depended on SOM neuron activity. These data identify a circuit that is sufficient to mediate long-range gamma-band coherence in the primary visual cortex.
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Affiliation(s)
- Richard Hakim
- Department of Molecular and Cell Biology, University of California, Berkeley, United States.,Helen Wills Neuroscience Institute, University of California, Berkeley, United States
| | - Kiarash Shamardani
- Department of Molecular and Cell Biology, University of California, Berkeley, United States.,Helen Wills Neuroscience Institute, University of California, Berkeley, United States
| | - Hillel Adesnik
- Department of Molecular and Cell Biology, University of California, Berkeley, United States.,Helen Wills Neuroscience Institute, University of California, Berkeley, United States
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12
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Abstract
Neocortical neurons tend to be coactive in groups called ensembles. However, sometimes, individual neurons also spike alone, independent of the ensemble. What processes regulate the transition between individual and cooperative action? Inspired by classical work in biochemistry, we apply the concept of neuronal cooperativity to explore this question. With a focus on neocortical inhibitory interneurons, we offer a working definition of neuronal cooperativity, review its recorded incidences and proposed mechanisms, and describe experimental approaches that will demonstrate and further describe this action. We suggest that cooperativity of "neuron teams" is manifested in vivo through their coactivity, as well as via the action of individual "soloist neurons" in the low end of the sigmoidal cooperativity curve. Finally, we explore the evidence for and implications of individual and team action of neurons.
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Affiliation(s)
- Mahesh M Karnani
- 1 Francis Crick Institute, London, UK.,2 King's College London IoPPN, London, UK
| | - Jesse Jackson
- 3 Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
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13
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Wang S, Borst A, Zaslavsky N, Tishby N, Segev I. Efficient encoding of motion is mediated by gap junctions in the fly visual system. PLoS Comput Biol 2017; 13:e1005846. [PMID: 29206224 PMCID: PMC5730180 DOI: 10.1371/journal.pcbi.1005846] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 12/14/2017] [Accepted: 10/16/2017] [Indexed: 01/10/2023] Open
Abstract
Understanding the computational implications of specific synaptic connectivity patterns is a fundamental goal in neuroscience. In particular, the computational role of ubiquitous electrical synapses operating via gap junctions remains elusive. In the fly visual system, the cells in the vertical-system network, which play a key role in visual processing, primarily connect to each other via axonal gap junctions. This network therefore provides a unique opportunity to explore the functional role of gap junctions in sensory information processing. Our information theoretical analysis of a realistic VS network model shows that within 10 ms following the onset of the visual input, the presence of axonal gap junctions enables the VS system to efficiently encode the axis of rotation, θ, of the fly’s ego motion. This encoding efficiency, measured in bits, is near-optimal with respect to the physical limits of performance determined by the statistical structure of the visual input itself. The VS network is known to be connected to downstream pathways via a subset of triplets of the vertical system cells; we found that because of the axonal gap junctions, the efficiency of this subpopulation in encoding θ is superior to that of the whole vertical system network and is robust to a wide range of signal to noise ratios. We further demonstrate that this efficient encoding of motion by this subpopulation is necessary for the fly's visually guided behavior, such as banked turns in evasive maneuvers. Because gap junctions are formed among the axons of the vertical system cells, they only impact the system’s readout, while maintaining the dendritic input intact, suggesting that the computational principles implemented by neural circuitries may be much richer than previously appreciated based on point neuron models. Our study provides new insights as to how specific network connectivity leads to efficient encoding of sensory stimuli. Understanding sensory stimuli from the environment and deciding how best to respond to it behaviorally is essential for survival. What makes organisms efficient in encoding these sensory stimuli? This study provides a novel view on this unresolved issue using the visual system of the fly. We show that a specific synaptic connectivity manifested via gap junctions (GJs) among axons in the Vertical System (VS) network leads to particularly high encoding efficiency of the axis of rotation of the fly’s ego motion. Due to these GJs, triplets of VS neurons (the VS5-6-7 triplet), which connect to a downstream motor system, encode motion stimuli at an efficiency close to the physical limit; this efficient encoding is necessary for evasive maneuvers that are critical for the fly to escape predators. We then suggest why GJs in the VS network enable such high encoding efficiency.
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Affiliation(s)
- Siwei Wang
- Department of Neurobiology, Hebrew University Jerusalem, Jerusalem, Israel
- * E-mail:
| | - Alexander Borst
- Max Planck Institute of Neurobiology, Martinstried, Munich, Germany
| | - Noga Zaslavsky
- The Edmond and Lily Safra Center for Brain Sciences, Hebrew University Jerusalem, Jerusalem, Israel
| | - Naftali Tishby
- The Edmond and Lily Safra Center for Brain Sciences, Hebrew University Jerusalem, Jerusalem, Israel
- Department of Computer Science, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Idan Segev
- Department of Neurobiology, Hebrew University Jerusalem, Jerusalem, Israel
- Max Planck Institute of Neurobiology, Martinstried, Munich, Germany
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14
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Coulon P, Landisman CE. The Potential Role of Gap Junctional Plasticity in the Regulation of State. Neuron 2017; 93:1275-1295. [PMID: 28334604 DOI: 10.1016/j.neuron.2017.02.041] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 01/20/2017] [Accepted: 02/22/2017] [Indexed: 11/19/2022]
Abstract
Electrical synapses are the functional correlate of gap junctions and allow transmission of small molecules and electrical current between coupled neurons. Instead of static pores, electrical synapses are actually plastic, similar to chemical synapses. In the thalamocortical system, gap junctions couple inhibitory neurons that are similar in their biochemical profile, morphology, and electrophysiological properties. We postulate that electrical synaptic plasticity among inhibitory neurons directly interacts with the switching between different firing patterns in a state-dependent and type-dependent manner. In neuronal networks, electrical synapses may function as a modifiable resonance feedback system that enables stable oscillations. Furthermore, the plasticity of electrical synapses may play an important role in regulation of state, synchrony, and rhythmogenesis in the mammalian thalamocortical system, similar to chemical synaptic plasticity. Based on their plasticity, rich diversity, and specificity, electrical synapses are thus likely to participate in the control of consciousness and attention.
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Affiliation(s)
- Philippe Coulon
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA 98101, USA.
| | - Carole E Landisman
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA 98101, USA.
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15
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Hatch RJ, Mendis GDC, Kaila K, Reid CA, Petrou S. Gap Junctions Link Regular-Spiking and Fast-Spiking Interneurons in Layer 5 Somatosensory Cortex. Front Cell Neurosci 2017; 11:204. [PMID: 28769764 PMCID: PMC5511827 DOI: 10.3389/fncel.2017.00204] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 06/28/2017] [Indexed: 11/24/2022] Open
Abstract
Gap junctions form electrical synapses that modulate neuronal activity by synchronizing action potential (AP) firing of cortical interneurons (INs). Gap junctions are thought to form predominantly within cortical INs of the same functional class and are therefore considered to act within discrete neuronal populations. Here, we challenge that view and show that the probability of electrical coupling is the same within and between regular-spiking (RS) and fast-spiking (FS) cortical INs in 16–21 days old mice. Firing properties of these two populations were distinct from other INs types including neurogliaform and low-threshold spiking (LTS) cells. We also demonstrate that pre-junctional APs can depolarize post-junctional neurons and increase the probability of firing. Our findings of frequent gap junction coupling between functionally distinct IN subtypes suggest that cortical IN networks are much more extensive and heterogeneous than previously thought. This may have implications on mechanisms ranging from cognitive functions to modulation of pathological states in epilepsy and other neurological disorders.
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Affiliation(s)
- Robert J Hatch
- The Florey Institute of Neuroscience and Mental Health, The University of MelbourneMelbourne, VIC, Australia
| | - G Dulini C Mendis
- Department of Mechanical Engineering, The University of MelbourneMelbourne, VIC, Australia
| | - Kai Kaila
- Department of Biosciences and Neuroscience Center (HiLife), The University of HelsinkiHelsinki, Finland
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health, The University of MelbourneMelbourne, VIC, Australia
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, The University of MelbourneMelbourne, VIC, Australia.,Department of Medicine (RMH), The University of MelbourneMelbourne, VIC, Australia.,ARC Centre of Excellence for Integrated Brain Function, The University of MelbourneMelbourne, VIC, Australia
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16
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Connors BW. Synchrony and so much more: Diverse roles for electrical synapses in neural circuits. Dev Neurobiol 2017; 77:610-624. [PMID: 28245529 DOI: 10.1002/dneu.22493] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/05/2017] [Accepted: 02/14/2017] [Indexed: 11/09/2022]
Abstract
Electrical synapses are neuronal gap junctions that are ubiquitous across brain regions and species. The biophysical properties of most electrical synapses are relatively simple-transcellular channels allow nearly ohmic, bidirectional flow of ionic current. Yet these connections can play remarkably diverse roles in different neural circuit contexts. Recent findings illustrate how electrical synapses may excite or inhibit, synchronize or desynchronize, augment or diminish rhythms, phase-shift, detect coincidences, enhance signals relative to noise, adapt, and interact with nonlinear membrane and transmitter-release mechanisms. Most of these functions are likely to be widespread in central nervous systems. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 610-624, 2017.
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Affiliation(s)
- Barry W Connors
- Department of Neuroscience, Brown University, Providence, Rhode Island
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17
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Phillips EA, Hasenstaub AR. Asymmetric effects of activating and inactivating cortical interneurons. eLife 2016; 5. [PMID: 27719761 PMCID: PMC5123863 DOI: 10.7554/elife.18383] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 10/09/2016] [Indexed: 11/16/2022] Open
Abstract
Bidirectional manipulations – activation and inactivation – are widely used to identify the functions supported by specific cortical interneuron types. Implicit in much of this work is the notion that tonic activation and inactivation will both produce valid, internally consistent insights into interneurons’ computational roles. Here, using single-unit recordings in auditory cortex of awake mice, we show that this may not generally hold true. Optogenetically manipulating somatostatin-positive (Sst+) or parvalbumin-positive (Pvalb+) interneurons while recording tone-responses showed that Sst+ inactivation increased response gain, while Pvalb+ inactivation weakened tuning and decreased information transfer, implying that these neurons support delineable computational functions. But activating Sst+ and Pvalb+ interneurons revealed no such differences. We used a simple network model to understand this asymmetry, and showed how relatively small changes in key parameters, such as spontaneous activity or strength of the light manipulation, determined whether activation and inactivation would produce consistent or paradoxical conclusions regarding interneurons’ computational functions. DOI:http://dx.doi.org/10.7554/eLife.18383.001 The brain processes information through the activity of many different types of neurons. A common assumption is that we can work out the role of each type of neuron by increasing or decreasing its activity experimentally and observing the consequences. Imagine, for example, that increasing the activity of a group of neurons boosts the formation of memories, whereas decreasing their activity has the opposite effect. Can we conclude that the natural role of those neurons is to support memory formation? This question has become increasingly pertinent in recent years, as advances in molecular genetic techniques such as optogenetics have made it easier to experimentally manipulate the activity of neurons. However, the ease with which these experiments can be done masks how difficult it can be to interpret the results. To test the assumption that dialing a neuron’s activity up or down provides a straightforward readout of its role in the brain, Phillips and Hasenstaub used optogenetics to inactivate two types of neurons in an area of the mouse brain responsible for processing sound. Inactivating each cell type produced different outcomes. The standard way of interpreting these results is to conclude that the neurons must therefore have different, separable roles. However, using optogenetics to increase the activity of the neurons revealed no such differences in the neurons’ roles. Using a computer model, Phillips and Hasenstaub showed that relatively small changes in factors such as the spontaneous activity of the neurons can affect the outcome of the experiments. Under certain circumstances, the two types of neurons respond in the same way to activation and inactivation; under other circumstances, they respond differently. The results presented by Phillips and Hasenstaub remind us that the conclusions we draw about a neuron’s role can be sensitive to how the cell was manipulated. Future studies should address how other aspects of experimental manipulations, such as their timing or pattern, affect the apparent behavior of neurons. DOI:http://dx.doi.org/10.7554/eLife.18383.002
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Affiliation(s)
- Elizabeth Ak Phillips
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, United States.,Center for Integrative Neuroscience, University of California San Francisco, San Francisco, United States.,Coleman Memorial Laboratory, University of California, San Francisco, San Francisco, United States.,Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, United States
| | - Andrea R Hasenstaub
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, United States.,Center for Integrative Neuroscience, University of California San Francisco, San Francisco, United States.,Coleman Memorial Laboratory, University of California, San Francisco, San Francisco, United States.,Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, United States
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18
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Yao XH, Wang M, He XN, He F, Zhang SQ, Lu W, Qiu ZL, Yu YC. Electrical coupling regulates layer 1 interneuron microcircuit formation in the neocortex. Nat Commun 2016; 7:12229. [PMID: 27510304 PMCID: PMC4987578 DOI: 10.1038/ncomms12229] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 06/15/2016] [Indexed: 02/06/2023] Open
Abstract
The coexistence of electrical and chemical synapses among interneurons is essential for interneuron function in the neocortex. However, it remains largely unclear whether electrical coupling between interneurons influences chemical synapse formation and microcircuit assembly during development. Here, we show that electrical and GABAergic chemical connections robustly develop between interneurons in neocortical layer 1 over a similar time course. Electrical coupling promotes action potential generation and synchronous firing between layer 1 interneurons. Furthermore, electrically coupled interneurons exhibit strong GABA-A receptor-mediated synchronous synaptic activity. Disruption of electrical coupling leads to a loss of bidirectional, but not unidirectional, GABAergic connections. Moreover, a reduction in electrical coupling induces an increase in excitatory synaptic inputs to layer 1 interneurons. Together, these findings strongly suggest that electrical coupling between neocortical interneurons plays a critical role in regulating chemical synapse development and precise formation of circuits.
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Affiliation(s)
- Xing-Hua Yao
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Min Wang
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Xiang-Nan He
- Centre for Computational Systems Biology and the School of Mathematical Sciences, Fudan University, Shanghai 200433, China
| | - Fei He
- Stem Cell Translational Research Center, Tongji Hospital, Tongji University School of Medicine, Shanghai 200092, China
| | - Shu-Qing Zhang
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Wenlian Lu
- Centre for Computational Systems Biology and the School of Mathematical Sciences, Fudan University, Shanghai 200433, China
| | - Zi-Long Qiu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and University of Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
| | - Yong-Chun Yu
- Institute of Neurobiology, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
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19
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Neske GT, Connors BW. Synchronized gamma-frequency inhibition in neocortex depends on excitatory-inhibitory interactions but not electrical synapses. J Neurophysiol 2016; 116:351-68. [PMID: 27121576 PMCID: PMC4969394 DOI: 10.1152/jn.00071.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 04/23/2016] [Indexed: 11/22/2022] Open
Abstract
Synaptic inhibition plays a crucial role in the precise timing of spiking activity in the cerebral cortex. Synchronized, rhythmic inhibitory activity in the gamma (30-80 Hz) range is thought to be especially important for the active, information-processing neocortex, but the circuit mechanisms that give rise to synchronized inhibition are uncertain. In particular, the relative contributions of reciprocal inhibitory connections, excitatory-inhibitory interactions, and electrical synapses to precise spike synchrony among inhibitory interneurons are not well understood. Here we describe experiments on mouse barrel cortex in vitro as it spontaneously generates slow (<1 Hz) oscillations (Up and Down states). During Up states, inhibitory postsynaptic currents (IPSCs) are generated at gamma frequencies and are more synchronized than excitatory postsynaptic currents (EPSCs) among neighboring pyramidal cells. Furthermore, spikes in homotypic pairs of interneurons are more synchronized than in pairs of pyramidal cells. Comparing connexin36 knockout and wild-type animals, we found that electrical synapses make a minimal contribution to synchronized inhibition during Up states. Estimations of the delays between EPSCs and IPSCs in single pyramidal cells showed that excitation often preceded inhibition by a few milliseconds. Finally, tonic optogenetic activation of different interneuron subtypes in the absence of excitation led to only weak synchrony of IPSCs in pairs of pyramidal neurons. Our results suggest that phasic excitatory inputs are indispensable for synchronized spiking in inhibitory interneurons during Up states and that electrical synapses play a minimal role.
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Affiliation(s)
- Garrett T Neske
- Department of Neuroscience, Brown University, Providence, Rhode Island
| | - Barry W Connors
- Department of Neuroscience, Brown University, Providence, Rhode Island
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20
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Liguz-Lecznar M, Urban-Ciecko J, Kossut M. Somatostatin and Somatostatin-Containing Neurons in Shaping Neuronal Activity and Plasticity. Front Neural Circuits 2016; 10:48. [PMID: 27445703 PMCID: PMC4927943 DOI: 10.3389/fncir.2016.00048] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 06/20/2016] [Indexed: 01/27/2023] Open
Abstract
Since its discovery over four decades ago, somatostatin (SOM) receives growing scientific and clinical interest. Being localized in the nervous system in a subset of interneurons somatostatin acts as a neurotransmitter or neuromodulator and its role in the fine-tuning of neuronal activity and involvement in synaptic plasticity and memory formation are widely recognized in the recent literature. Combining transgenic animals with electrophysiological, anatomical and molecular methods allowed to characterize several subpopulations of somatostatin-containing interneurons possessing specific anatomical and physiological features engaged in controlling the output of cortical excitatory neurons. Special characteristic and connectivity of somatostatin-containing neurons set them up as significant players in shaping activity and plasticity of the nervous system. However, somatostatin is not just a marker of particular interneuronal subpopulation. Somatostatin itself acts pre- and postsynaptically, modulating excitability and neuronal responses. In the present review, we combine the knowledge regarding somatostatin and somatostatin-containing interneurons, trying to incorporate it into the current view concerning the role of the somatostatinergic system in cortical plasticity.
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Affiliation(s)
- Monika Liguz-Lecznar
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology Warsaw, Poland
| | - Joanna Urban-Ciecko
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental BiologyWarsaw, Poland; Department of Biological Sciences and Center for the Neural Basis of Cognition, Carnegie Mellon UniversityPittsburgh, PA, USA
| | - Malgorzata Kossut
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental BiologyWarsaw, Poland; Department of Psychology, University of Social Sciences and Humanities (SWPS)Warsaw, Poland
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21
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Amsalem O, Van Geit W, Muller E, Markram H, Segev I. From Neuron Biophysics to Orientation Selectivity in Electrically Coupled Networks of Neocortical L2/3 Large Basket Cells. Cereb Cortex 2016; 26:3655-3668. [PMID: 27288316 PMCID: PMC4961030 DOI: 10.1093/cercor/bhw166] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In the neocortex, inhibitory interneurons of the same subtype are electrically coupled with each other via dendritic gap junctions (GJs). The impact of multiple GJs on the biophysical properties of interneurons and thus on their input processing is unclear. The present experimentally based theoretical study examined GJs in L2/3 large basket cells (L2/3 LBCs) with 3 goals in mind: (1) To evaluate the errors due to GJs in estimating the cable properties of individual L2/3 LBCs and suggest ways to correct these errors when modeling these cells and the networks they form; (2) to bracket the GJ conductance value (0.05-0.25 nS) and membrane resistivity (10 000-40 000 Ω cm(2)) of L2/3 LBCs; these estimates are tightly constrained by in vitro input resistance (131 ± 18.5 MΩ) and the coupling coefficient (1-3.5%) of these cells; and (3) to explore the functional implications of GJs, and show that GJs: (i) dynamically modulate the effective time window for synaptic integration; (ii) improve the axon's capability to encode rapid changes in synaptic inputs; and (iii) reduce the orientation selectivity, linearity index, and phase difference of L2/3 LBCs. Our study provides new insights into the role of GJs and calls for caution when using in vitro measurements for modeling electrically coupled neuronal networks.
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Affiliation(s)
| | - Werner Van Geit
- Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL) Biotech Campus, 1202 Geneva, Switzerland
| | - Eilif Muller
- Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL) Biotech Campus, 1202 Geneva, Switzerland
| | - Henry Markram
- Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL) Biotech Campus, 1202 Geneva, Switzerland
| | - Idan Segev
- Department of Neurobiology.,Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, 9190401 Jerusalem, Israel
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22
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Abstract
Somatostatin-expressing GABAergic neurons constitute a major class of inhibitory neurons in the mammalian cortex and are characterized by dense wiring into the local network and high basal firing activity that persists in the absence of synaptic input. This firing provides both GABA type A receptor (GABAAR)- and GABABR-mediated inhibition that operates at fast and slow timescales. The activity of somatostatin-expressing neurons is regulated by brain state, during learning and in rewarded behaviour. Here, we review recent advances in our understanding of how this class of cells can control network activity, with specific reference to how this is constrained by their anatomical and electrophysiological properties.
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23
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Inan M, Zhao M, Manuszak M, Karakaya C, Rajadhyaksha AM, Pickel VM, Schwartz TH, Goldstein PA, Manfredi G. Energy deficit in parvalbumin neurons leads to circuit dysfunction, impaired sensory gating and social disability. Neurobiol Dis 2016; 93:35-46. [PMID: 27105708 DOI: 10.1016/j.nbd.2016.04.004] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 04/13/2016] [Accepted: 04/15/2016] [Indexed: 12/17/2022] Open
Abstract
Parvalbumin-expressing, fast spiking interneurons have high-energy demands, which make them particularly susceptible to energy impairment. Recent evidence suggests a link between mitochondrial dysfunction in fast spiking cortical interneurons and neuropsychiatric disorders. However, the effect of mitochondrial dysfunction restricted to parvalbumin interneurons has not been directly addressed in vivo. To investigate the consequences of mitochondrial dysfunction in parvalbumin interneurons in vivo, we generated conditional knockout mice with a progressive decline in oxidative phosphorylation by deleting cox10 gene selectively in parvalbumin neurons (PV-Cox10 CKO). Cox10 ablation results in defective assembly of cytochrome oxidase, the terminal enzyme of the electron transfer chain, and leads to mitochondrial bioenergetic dysfunction. PV-Cox10 CKO mice showed a progressive loss of cytochrome oxidase in cortical parvalbumin interneurons. Cytochrome oxidase protein levels were significantly reduced starting at postnatal day 60, and this was not associated with a change in parvalbumin interneuron density. Analyses of intrinsic electrophysiological properties in layer 5 primary somatosensory cortex revealed that parvalbumin interneurons could not sustain their typical high frequency firing, and their overall excitability was enhanced. An increase in both excitatory and inhibitory input onto parvalbumin interneurons was observed in PV-Cox10 CKO mice, resulting in a disinhibited network with an imbalance of excitation/inhibition. Investigation of network oscillations in PV-Cox10 CKO mice, using local field potential recordings in anesthetized mice, revealed significantly increased gamma and theta frequency oscillation power in both medial prefrontal cortex and hippocampus. PV-Cox10 CKO mice did not exhibit muscle strength or gross motor activity deficits in the time frame of the experiments, but displayed impaired sensory gating and sociability. Taken together, these data reveal that mitochondrial dysfunction in parvalbumin interneurons can alter their intrinsic physiology and network connectivity, resulting in behavioral alterations similar to those observed in neuropsychiatric disorders, such as schizophrenia and autism.
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Affiliation(s)
- Melis Inan
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States
| | - Mingrui Zhao
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States; Department of Neurological Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Monica Manuszak
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States
| | - Cansu Karakaya
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States
| | - Anjali M Rajadhyaksha
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States; Department of Pediatric Neurology, Weill Cornell Medical College, New York, NY, United States; Department of Anesthesiology, Weill Cornell Medical College, New York, NY, United States
| | - Virginia M Pickel
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States
| | - Theodore H Schwartz
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States; Department of Neurological Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Peter A Goldstein
- Department of Anesthesiology, Weill Cornell Medical College, New York, NY, United States; Department of Medicine, Weill Cornell Medical College, New York, NY, United States.
| | - Giovanni Manfredi
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY, United States.
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24
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Wiesman AI. Homotypic synaptic coupling and the cellular bases of gamma oscillatory activity. J Neurophysiol 2016. [PMID: 26224777 DOI: 10.1152/jn.00689.2015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the importance of gamma oscillatory activity in brain function is well established, the exact contributions of neuron and synapse type remains unclear. In their study, Hu and Agmon (J Neurophysiol 114: 624-637, 2015) show that precision as well as firing rate dependence of gamma synchrony rely primarily on cellular coupling type (chemical, electrical, or dual), rather than properties intrinsic to cell type. These findings are discussed with a focus on current ramifications and the implications for future research.
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Affiliation(s)
- Alex I Wiesman
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska
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