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Theyel BB, Stevenson RJ, Connors BW. Activity-Dependent Ectopic Spiking in Parvalbumin-Expressing Interneurons of the Neocortex. eNeuro 2024; 11:ENEURO.0314-23.2024. [PMID: 38637152 PMCID: PMC11069434 DOI: 10.1523/eneuro.0314-23.2024] [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: 08/23/2023] [Revised: 03/12/2024] [Accepted: 03/17/2024] [Indexed: 04/20/2024] Open
Abstract
Canonically, action potentials of most mammalian neurons initiate at the axon initial segment (AIS) and propagate bidirectionally: orthodromically along the distal axon and retrogradely into the soma and dendrites. Under some circumstances, action potentials may initiate ectopically, at sites distal to the AIS, and propagate antidromically along the axon. These "ectopic action potentials" (EAPs) have been observed in experimental models of seizures and chronic pain, and more rarely in nonpathological forebrain neurons. Here we report that a large majority of parvalbumin-expressing (PV+) interneurons in the upper layers of mouse neocortex, from both orbitofrontal and primary somatosensory areas, fire EAPs after sufficient activation of their somata. Somatostatin-expressing interneurons also fire EAPs, though less robustly. Ectopic firing in PV+ cells occurs in varying temporal patterns and can persist for several seconds. PV+ cells evoke strong synaptic inhibition in pyramidal neurons and interneurons and play critical roles in cortical function. Our results suggest that ectopic spiking of PV+ interneurons is common and may contribute to both normal and pathological network functions of the neocortex.
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Affiliation(s)
- Brian B Theyel
- Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, Rhode Island 02912
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
- Care New England Medical Group, Providence, Rhode Island 02906
| | - Rachel J Stevenson
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | - Barry W Connors
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
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Rózsa M, Tóth M, Oláh G, Baka J, Lákovics R, Barzó P, Tamás G. Temporal disparity of action potentials triggered in axon initial segments and distal axons in the neocortex. SCIENCE ADVANCES 2023; 9:eade4511. [PMID: 37824608 PMCID: PMC10569705 DOI: 10.1126/sciadv.ade4511] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 04/11/2023] [Indexed: 10/14/2023]
Abstract
Neural population activity determines the timing of synaptic inputs, which arrive to dendrites, cell bodies, and axon initial segments (AISs) of cortical neurons. Action potential initiation in the AIS (AIS-APs) is driven by input integration, and the phase preference of AIS-APs during network oscillations is characteristic to cell classes. Distal regions of cortical axons do not receive synaptic inputs, yet experimental induction protocols can trigger retroaxonal action potentials (RA-APs) in axons distal from the soma. We report spontaneously occurring RA-APs in human and rodent cortical interneurons that appear uncorrelated to inputs and population activity. Network-linked triggering of AIS-APs versus input-independent timing of RA-APs of the same interneurons results in disparate temporal contribution of a single cell to in vivo network operation through perisomatic and distal axonal firing.
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Affiliation(s)
- Márton Rózsa
- ELKH-SZTE Research Group for Cortical Microcircuits, University of Szeged, Szeged, Hungary
| | - Martin Tóth
- ELKH-SZTE Research Group for Cortical Microcircuits, University of Szeged, Szeged, Hungary
| | - Gáspár Oláh
- ELKH-SZTE Research Group for Cortical Microcircuits, University of Szeged, Szeged, Hungary
| | - Judith Baka
- ELKH-SZTE Research Group for Cortical Microcircuits, University of Szeged, Szeged, Hungary
| | - Rajmund Lákovics
- ELKH-SZTE Research Group for Cortical Microcircuits, University of Szeged, Szeged, Hungary
| | - Pál Barzó
- Department of Neurosurgery, University of Szeged, Szeged, Hungary
| | - Gábor Tamás
- ELKH-SZTE Research Group for Cortical Microcircuits, University of Szeged, Szeged, Hungary
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Chittajallu R, Auville K, Mahadevan V, Lai M, Hunt S, Calvigioni D, Pelkey KA, Zaghloul KA, McBain CJ. Activity-dependent tuning of intrinsic excitability in mouse and human neurogliaform cells. eLife 2020; 9:57571. [PMID: 32496194 PMCID: PMC7299336 DOI: 10.7554/elife.57571] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 06/02/2020] [Indexed: 12/15/2022] Open
Abstract
The ability to modulate the efficacy of synaptic communication between neurons constitutes an essential property critical for normal brain function. Animal models have proved invaluable in revealing a wealth of diverse cellular mechanisms underlying varied plasticity modes. However, to what extent these processes are mirrored in humans is largely uncharted thus questioning their relevance in human circuit function. In this study, we focus on neurogliaform cells, that possess specialized physiological features enabling them to impart a widespread inhibitory influence on neural activity. We demonstrate that this prominent neuronal subtype, embedded in both mouse and human neural circuits, undergo remarkably similar activity-dependent modulation manifesting as epochs of enhanced intrinsic excitability. In principle, these evolutionary conserved plasticity routes likely tune the extent of neurogliaform cell mediated inhibition thus constituting canonical circuit mechanisms underlying human cognitive processing and behavior.
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Affiliation(s)
- Ramesh Chittajallu
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Kurt Auville
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Vivek Mahadevan
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Mandy Lai
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Steven Hunt
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Daniela Calvigioni
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Kenneth A Pelkey
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Kareem A Zaghloul
- Surgical Neurology Branch, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Chris J McBain
- Laboratory of Cellular and Synaptic Physiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
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Neuronal expression of c-Fos after epicortical and intracortical electric stimulation of the primary visual cortex. J Chem Neuroanat 2016; 77:121-128. [PMID: 27364963 DOI: 10.1016/j.jchemneu.2016.06.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 06/25/2016] [Indexed: 11/20/2022]
Abstract
Electrical stimulation of the primary visual cortex (V1) is an experimental approach for visual prostheses. We here compared the response to intracortical and epicortical stimulation of the primary visual cortex by using c-Fos immunoreactivity as a marker for neuronal activation. The primary visual cortex of male Sprague Dawley rats was unilaterally stimulated for four hours using bipolar electrodes placed either intracortically in layer IV (n=26) or epicortically (n=20). Four different current intensities with a constant pulse width of 200μs and a constant frequency of 10Hz were used, for intracortical stimulation with an intensity of 0μA (sham-stimulation), 10μA, 20μA and 40μA, and for epicortical stimulation 0μA, 400μA, 600μA and 800μA. Subsequently all animals underwent c-Fos immunostaining and c-Fos expression was assessed in layer I-VI of the primary visual cortex within 200μm and 400μm distance to the stimulation site. C-Fos expression was higher after intracortical stimulation compared to epicortical stimulation, even though ten times lower current intensities were applied. Furthermore intracortical stimulation resulted in more focal neuronal activation than epicortical stimulation. C-Fos expression was highest after intracortical stimulation with 20μA compared to all other intensities. Epicortical stimulation showed a linear increase of c-Fos expression with the highest expression at 800μA. Sham stimulation showed similar expression of c-Fos in both hemispheres. The contralateral hemisphere was not affected by intracortical or epicortical stimulation of either intensities. In summary, intracortical stimulation resulted in more focal neuronal activation with less current than epicortical stimulation. This model may be used as a simple but reliable model to evaluate electrodes for microstimulation of the primary visual cortex before testing in more complex settings.
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