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Network Properties Revealed during Multi-Scale Calcium Imaging of Seizure Activity in Zebrafish. eNeuro 2019; 6:eN-NWR-0041-19. [PMID: 30895220 PMCID: PMC6424556 DOI: 10.1523/eneuro.0041-19.2019] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 02/08/2019] [Indexed: 12/02/2022] Open
Abstract
Seizures are characterized by hypersynchronization of neuronal networks. Understanding these networks could provide a critical window for therapeutic control of recurrent seizure activity, i.e., epilepsy. However, imaging seizure networks has largely been limited to microcircuits in vitro or small “windows” in vivo. Here, we combine fast confocal imaging of genetically encoded calcium indicator (GCaMP)-expressing larval zebrafish with local field potential (LFP) recordings to study epileptiform events at whole-brain and single-neuron levels in vivo. Using an acute seizure model (pentylenetetrazole, PTZ), we reliably observed recurrent electrographic ictal-like events associated with generalized activation of all major brain regions and uncovered a well-preserved anterior-to-posterior seizure propagation pattern. We also examined brain-wide network synchronization and spatiotemporal patterns of neuronal activity in the optic tectum microcircuit. Brain-wide and single-neuronal level analysis of PTZ-exposed and 4-aminopyridine (4-AP)-exposed zebrafish revealed distinct network dynamics associated with seizure and non-seizure hyperexcitable states, respectively. Neuronal ensembles, comprised of coactive neurons, were also uncovered during interictal-like periods. Taken together, these results demonstrate that macro- and micro-network calcium motifs in zebrafish may provide a greater understanding of epilepsy.
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Jacob T, Lillis KP, Wang Z, Swiercz W, Rahmati N, Staley KJ. A Proposed Mechanism for Spontaneous Transitions between Interictal and Ictal Activity. J Neurosci 2019; 39:557-575. [PMID: 30446533 PMCID: PMC6335741 DOI: 10.1523/jneurosci.0719-17.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 10/23/2018] [Accepted: 10/31/2018] [Indexed: 11/21/2022] Open
Abstract
Epileptic networks are characterized by two outputs: brief interictal spikes and rarer, more prolonged seizures. Although either output state is readily modeled in silico and induced experimentally, the transition mechanisms are unknown, in part because no models exhibit both output states spontaneously. In silico small-world neural networks were built using single-compartment neurons whose physiological parameters were derived from dual whole-cell recordings of pyramidal cells in organotypic hippocampal slice cultures that were generating spontaneous seizure-like activity. In silico, neurons were connected by abundant local synapses and rare long-distance synapses. Activity-dependent synaptic depression and gradual recovery delimited synchronous activity. Full synaptic recovery engendered interictal population spikes that spread via long-distance synapses. When synaptic recovery was incomplete, postsynaptic neurons required coincident activation of multiple presynaptic terminals to reach firing threshold. Only local connections were sufficiently dense to spread activity under these conditions. This coalesced network activity into traveling waves whose velocity varied with synaptic recovery. Seizures were comprised of sustained traveling waves that were similar to those recorded during experimental and human neocortical seizures. Sustained traveling waves occurred only when wave velocity, network dimensions, and the rate of synaptic recovery enabled wave reentry into previously depressed areas at precisely ictogenic levels of synaptic recovery. Wide-field, cellular-resolution GCamP7b calcium imaging demonstrated similar initial patterns of activation in the hippocampus, although the anatomical distribution of traveling waves of synaptic activation was altered by the pattern of synaptic connectivity in the organotypic hippocampal cultures.SIGNIFICANCE STATEMENT When computerized distributed neural network models are required to generate both features of epileptic networks (i.e., spontaneous interictal population spikes and seizures), the network structure is substantially constrained. These constraints provide important new hypotheses regarding the nature of epileptic networks and mechanisms of seizure onset.
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Affiliation(s)
- Theju Jacob
- Massachusetts General Hospital, Boston, Massachusetts 02114
- Harvard Medical School, Boston, MA 02115
| | - Kyle P Lillis
- Massachusetts General Hospital, Boston, Massachusetts 02114
- Harvard Medical School, Boston, MA 02115
| | - Zemin Wang
- Brigham and Women's Hospital, Boston, MA 02115, and
- Harvard Medical School, Boston, MA 02115
| | - Waldemar Swiercz
- Massachusetts General Hospital, Boston, Massachusetts 02114
- Harvard Medical School, Boston, MA 02115
| | - Negah Rahmati
- Massachusetts General Hospital, Boston, Massachusetts 02114
- Harvard Medical School, Boston, MA 02115
| | - Kevin J Staley
- Massachusetts General Hospital, Boston, Massachusetts 02114,
- Harvard Medical School, Boston, MA 02115
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Kulkarni R, Vandenberghe M, Thunemann M, James F, Andreassen OA, Djurovic S, Devor A, Miller EW. In Vivo Two-Photon Voltage Imaging with Sulfonated Rhodamine Dyes. ACS CENTRAL SCIENCE 2018; 4:1371-1378. [PMID: 30410975 PMCID: PMC6202643 DOI: 10.1021/acscentsci.8b00422] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Indexed: 05/24/2023]
Abstract
Optical methods that rely on fluorescence for mapping changes in neuronal membrane potential in the brains of awake animals provide a powerful way to interrogate the activity of neurons that underlie neural computations ranging from sensation and perception to learning and memory. To achieve this goal, fluorescent indicators should be bright, highly sensitive to small changes in membrane potential, nontoxic, and excitable with infrared light. We report a new class of fluorescent, voltage-sensitive dyes: sulfonated rhodamine voltage reporters (sRhoVR), synthetic fluorophores with high voltage sensitivity, excellent two-photon performance, and compatibility in intact mouse brains. sRhoVR dyes are based on a tetramethyl rhodamine fluorophore coupled to a phenylenevinylene molecular wire/diethyl aniline voltage-sensitive domain. When applied to cells, sRhoVR dyes localize to the plasma membrane and respond to membrane depolarization with a fluorescence increase. The best of the new dyes, sRhoVR 1, displays a 44% ΔF/F increase in fluorescence per 100 mV change, emits at 570 nm, and possesses excellent two-photon absorption of approximately 200 GM at 840 nm. sRhoVR 1 can detect action potentials in cultured rat hippocampal neurons under both single- and two-photon illumination with sufficient speed and sensitivity to report on action potentials in single trials, without perturbing underlying physiology or membrane properties. The combination of speed, sensitivity, and brightness under two-photon illumination makes sRhoVR 1 a promising candidate for in vivo imaging in intact brains. We show sRhoVR powerfully complements electrode-based modes of neuronal activity recording in the mouse brain by recording neuronal transmembrane potentials from the neuropil of layer 2/3 of the mouse barrel cortex in concert with extracellularly recorded local field potentials (LFPs). sRhoVR imaging reveals robust depolarization in response to whisker stimulation; concurrent electrode recordings reveal negative deflections in the LFP recording, consistent with the canonical thalamocortical response. Importantly, sRhoVR 1 can be applied in mice with chronic optical windows, presaging its utility in dissecting and resolving voltage dynamics using two-photon functional imaging in awake, behaving animals.
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Affiliation(s)
- Rishikesh
U. Kulkarni
- Department
of Chemistry, Department of Molecular and Cell Biology, and Helen Wills Neuroscience
Institute, University of California, Berkeley, California 94720, United States
| | - Matthieu Vandenberghe
- Department of Neurosciences and Department of Radiology, University of California, San
Diego, California 92093, United States
- NORMENT − KG Jebsen
Centre for Psychosis Research, Division
of Mental Health and Addiction, Oslo University Hospital
and University of Oslo and Department of Medical Genetics, Oslo University
Hospital, 0407 Oslo, Norway
| | - Martin Thunemann
- Department of Neurosciences and Department of Radiology, University of California, San
Diego, California 92093, United States
| | - Feroz James
- Department
of Chemistry, Department of Molecular and Cell Biology, and Helen Wills Neuroscience
Institute, University of California, Berkeley, California 94720, United States
| | - Ole A. Andreassen
- NORMENT − KG Jebsen
Centre for Psychosis Research, Division
of Mental Health and Addiction, Oslo University Hospital
and University of Oslo and Department of Medical Genetics, Oslo University
Hospital, 0407 Oslo, Norway
| | - Srdjan Djurovic
- NORMENT − KG Jebsen
Centre for Psychosis Research, Division
of Mental Health and Addiction, Oslo University Hospital
and University of Oslo and Department of Medical Genetics, Oslo University
Hospital, 0407 Oslo, Norway
| | - Anna Devor
- Department of Neurosciences and Department of Radiology, University of California, San
Diego, California 92093, United States
- Martinos
Center for Biomedical Imaging, Massachusetts
General Hospital, Charlestown, Massachusetts 02129, United States
| | - Evan W. Miller
- Department
of Chemistry, Department of Molecular and Cell Biology, and Helen Wills Neuroscience
Institute, University of California, Berkeley, California 94720, United States
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Rossi LF, Kullmann DM, Wykes RC. The Enlightened Brain: Novel Imaging Methods Focus on Epileptic Networks at Multiple Scales. Front Cell Neurosci 2018; 12:82. [PMID: 29632475 PMCID: PMC5879108 DOI: 10.3389/fncel.2018.00082] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/08/2018] [Indexed: 11/24/2022] Open
Abstract
Epilepsy research is rapidly adopting novel fluorescence optical imaging methods to tackle unresolved questions on the cellular and circuit mechanisms of seizure generation and evolution. State of the art two-photon microscopy and wide-field fluorescence imaging can record the activity in epileptic networks at multiple scales, from neuronal microcircuits to brain-wide networks. These approaches exploit transgenic and viral technologies to target genetically encoded calcium and voltage sensitive indicators to subclasses of neurons, and achieve genetic specificity, spatial resolution and scalability that can complement electrophysiological recordings from awake animal models of epilepsy. Two-photon microscopy is well suited to study single neuron dynamics during interictal and ictal events, and highlight the differences between the activity of excitatory and inhibitory neuronal classes in the focus and propagation zone. In contrast, wide-field fluorescence imaging provides mesoscopic recordings from the entire cortical surface, necessary to investigate seizure propagation pathways, and how the unfolding of epileptic events depends on the topology of brain-wide functional connectivity. Answering these questions will inform pre-clinical studies attempting to suppress seizures with gene therapy, optogenetic or chemogenetic strategies. Dissecting which network nodes outside the seizure onset zone are important for seizure generation, propagation and termination can be used to optimize current and future evaluation methods to identify an optimal surgical strategy.
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Affiliation(s)
- L Federico Rossi
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
| | - Robert C Wykes
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
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Déjà Vu: Same Pattern of Neuron Activation From Seizure to Seizure, Only the Timing Changes. Epilepsy Curr 2018; 18:131-132. [PMID: 29643754 DOI: 10.5698/1535-7597.18.2.131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Li L, Kriukova K, Engel J, Bragin A. Seizure development in the acute intrahippocampal epileptic focus. Sci Rep 2018; 8:1423. [PMID: 29362494 PMCID: PMC5780458 DOI: 10.1038/s41598-018-19675-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 01/05/2018] [Indexed: 01/29/2023] Open
Abstract
Currently, an epileptic seizure is considered to involve a temporary network that exists for a finite period of time. Formation of this network evolves through spread of epileptiform activity from a seizure onset zone (SOZ). Propagation of seizures evoked by kainic acid injection in hippocampus to different brain areas was analyzed at macro- and micro-intervals. The mean latency of seizure occurrence in different brain areas varied between 0.5 sec and 85 sec (mean 14.9 ± 14.5 (SD)), and it increased after each consecutive seizure in areas located contralateral to the area of injection, but not in the ipsilateral sites. We have shown that only 41% of epileptic individual events in target brain areas were driven by epileptic events generated in the SOZ once the seizure began. Fifty-nine percent of epileptiform events in target areas occurred one millisecond before or after events in the SOZ. These data illustrate that during seizure maintenance, only some individual epileptiform events in areas outside of SOZ could be consistently triggered by the SOZ; and the majority must be triggered by a driver located outside the SOZ or brain areas involved in ictal activity could be coupled to each other via an unknown mechanism such as stochastic resonance.
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Affiliation(s)
- Lin Li
- Department of Neurology, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA
| | - Kseniia Kriukova
- Department of Neurology, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA
- I.M. Sechenov First Moscow State Medical University, Moscow, Russia
| | - Jerome Engel
- Department of Neurology, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA.
- Department of Neurobiology, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA.
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA.
- Brain Research Institute, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA.
| | - Anatol Bragin
- Department of Neurology, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA.
- Brain Research Institute, David Geffen School of Medicine at University of California Los Angeles, 710 Westwood Plaza, Los Angeles, CA, 90095, USA.
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