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Ashtari M, Cook P, Lipin M, Yu Y, Ying GS, Maguire A, Bennett J, Gee J, Zhang H. Dynamic structural remodeling of the human visual system prompted by bilateral retinal gene therapy. CURRENT RESEARCH IN NEUROBIOLOGY 2023; 4:100089. [PMID: 37397812 PMCID: PMC10313860 DOI: 10.1016/j.crneur.2023.100089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 02/03/2023] [Accepted: 05/01/2023] [Indexed: 07/04/2023] Open
Abstract
The impact of changes in visual input on neuronal circuitry is complex and much of our knowledge on human brain plasticity of the visual systems comes from animal studies. Reinstating vision in a group of patients with low vision through retinal gene therapy creates a unique opportunity to dynamically study the underlying process responsible for brain plasticity. Historically, increases in the axonal myelination of the visual pathway has been the biomarker for brain plasticity. Here, we demonstrate that to reach the long-term effects of myelination increase, the human brain may undergo demyelination as part of a plasticity process. The maximum change in dendritic arborization of the primary visual cortex and the neurite density along the geniculostriate tracks occurred at three months (3MO) post intervention, in line with timing for the peak changes in postnatal synaptogenesis within the visual cortex reported in animal studies. The maximum change at 3MO for both the gray and white matter significantly correlated with patients' clinical responses to light stimulations called full field sensitivity threshold (FST). Our results shed a new light on the underlying process of brain plasticity by challenging the concept of increase myelination being the hallmark of brain plasticity and instead reinforcing the idea of signal speed optimization as a dynamic process for brain plasticity.
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Affiliation(s)
- Manzar Ashtari
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA, 19104, United States
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104, United States
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Philip Cook
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Mikhail Lipin
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Yinxi Yu
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Gui-Shuang Ying
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Albert Maguire
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA, 19104, United States
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Jean Bennett
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA, 19104, United States
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - James Gee
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, 19104, United States
| | - Hui Zhang
- Centre for Medical Image Computing, University College London, London, United Kingdom
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Kloosterboer E, Funke K. Repetitive transcranial magnetic stimulation recovers cortical map plasticity induced by sensory deprivation due to deafferentiation. J Physiol 2019; 597:4025-4051. [PMID: 31145483 PMCID: PMC6852264 DOI: 10.1113/jp277507] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 05/17/2019] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Partial sensory deprivation (deafferentation) by removing whiskers from the rat snout resulted in a reduced responsiveness of related cortical representations. Repetitive transcranial magnetic stimulation (three blocks of intermittent theta-burst) applied for 5 days in combination with sensory exploration restored the normal responsiveness level of the deafferented barrel cortex. However, intracortical inhibition (lateral and recurrent) appeared to be reduced after repetitive transcranial magnetic stimulation, probably as the cause of improved responsiveness. Repetitive transcranial magnetic stimulation also reduced the asymmetry of the lateral spread of sensory activity. ABSTRACT Repetitive transcranial magnetic stimulation (rTMS) modulates human cortical excitability. It has the potential to support recovery to normal cortical function when the excitation-inhibition balance is altered (e.g. after a stroke or loss of sensory input). We tested cortical map plasticity on the basis of sensory responses (local field potentials, LFPs) and expression of neuronal activity marker proteins within the barrel cortex of rats receiving either active or sham rTMS after selective unilateral deafferentation by whiskers plucking. Rats received daily rTMS [intermittent theta-burst (iTBS), active or sham] for 5 days before exploring an enriched environment. Our previous studies indicated a disinhibitory effect of iTBS on cortical activity. Therefore, we also expected disinhibitory effects if deafferentation causes depression of sensory responses. Deafferentation resulted in an acute general reduction of sensory responsiveness and enhanced expression of inhibitory activity markers (GAD67, parvalbumin) in the deafferented hemisphere. Active but not sham-iTBS-rTMS normalized these measures. The stronger caudal-to-frontal horizontal spread of activity across barrels was reduced after deafferentation but not restored after active iTBS, despite generally increased responses. Fitting the LFP data with a computational model of different strengths and types of excitatory and inhibitory connections further revealed an iTBS-induced reduction of lateral and recurrent inhibition as the most probable scenario. Whether the disinhibitory effect of iTBS for the restoration of normal cortical function in the acute phase of depression after deafferentiation is also beneficial in humans remains to be demonstrated. As recently discussed, disinhibition appears to be required to open a window for neuronal plasticity.
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Affiliation(s)
- Ellen Kloosterboer
- Department of Neurophysiology, Medical Faculty, Ruhr-University Bochum, Bochum, Germany
| | - Klaus Funke
- Department of Neurophysiology, Medical Faculty, Ruhr-University Bochum, Bochum, Germany
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Krieger P, de Kock CPJ, Frick A. Calcium Dynamics in Basal Dendrites of Layer 5A and 5B Pyramidal Neurons Is Tuned to the Cell-Type Specific Physiological Action Potential Discharge. Front Cell Neurosci 2017; 11:194. [PMID: 28744201 PMCID: PMC5504123 DOI: 10.3389/fncel.2017.00194] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 06/21/2017] [Indexed: 11/13/2022] Open
Abstract
Layer 5 (L5) is a major neocortical output layer containing L5A slender-tufted (L5A-st) and L5B thick-tufted (L5B-tt) pyramidal neurons. These neuron types differ in their in vivo firing patterns, connectivity and dendritic morphology amongst other features, reflecting their specific functional role within the neocortical circuits. Here, we asked whether the active properties of the basal dendrites that receive the great majority of synaptic inputs within L5 differ between these two pyramidal neuron classes. To quantify their active properties, we measured the efficacy with which action potential (AP) firing patterns backpropagate along the basal dendrites by measuring the accompanying calcium transients using two-photon laser scanning microscopy in rat somatosensory cortex slices. For these measurements we used both "artificial" three-AP patterns and more complex physiological AP patterns that were previously recorded in anesthetized rats in L5A-st and L5B-tt neurons in response to whisker stimulation. We show that AP patterns with relatively few APs (3APs) evoke a calcium response in L5B-tt, but not L5A-st, that is dependent on the temporal pattern of the three APs. With more complex in vivo recorded AP patterns, the average calcium response was similar in the proximal dendrites but with a decay along dendrites (measured up to 100 μm) of L5B-tt but not L5A-st neurons. Interestingly however, the whisker evoked AP patterns-although very different for the two cell types-evoke similar calcium responses. In conclusion, although the effectiveness with which different AP patterns evoke calcium transients vary between L5A-st and L5B-tt cell, the calcium influx appears to be tuned such that whisker-evoked calcium transients are within the same dynamic range for both cell types.
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Affiliation(s)
- Patrik Krieger
- Department of Cell Physiology, Max Planck Institute for Medical ResearchHeidelberg, Germany.,Department of Systems Neuroscience, Medical Faculty, Ruhr University BochumBochum, Germany
| | - Christiaan P J de Kock
- Department of Cell Physiology, Max Planck Institute for Medical ResearchHeidelberg, Germany.,Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research (CNCR), VU University AmsterdamAmsterdam, Netherlands
| | - Andreas Frick
- Department of Cell Physiology, Max Planck Institute for Medical ResearchHeidelberg, Germany.,INSERM, Neurocentre Magendie, U1215Bordeaux, France.,University of Bordeaux, Neurocentre Magendie, U1215Bordeaux, France
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Papaioannou S, Brigham L, Krieger P. Sensory deprivation during early development causes an increased exploratory behavior in a whisker-dependent decision task. Brain Behav 2013; 3:24-34. [PMID: 23408764 PMCID: PMC3568787 DOI: 10.1002/brb3.102] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 09/19/2012] [Accepted: 10/09/2012] [Indexed: 11/08/2022] Open
Abstract
Stimulation of sensory pathways is important for the normal development of cortical sensory areas, and impairments in the normal development can have long-lasting effect on animal's behavior. In particular, disturbances that occur early in development can cause permanent changes in brain structure and function. The behavioral effect of early sensory deprivation was studied in the mouse whisker system using a protocol to induce a 1-week sensory deprivation immediately after birth. Only two rows of whiskers were spared (C and D rows), and the rest were deprived, to create a situation where an unbalanced sensory input, rather than a complete loss of input, causes a reorganization of the sensory map. Sensory deprivation increased the barrel size ratio of the spared CD rows compared with the deprived AB rows; thus, the map reorganization is likely due, at least in part, to a rewiring of thalamocortical projections. The behavioral effect of such a map reorganization was investigated in the gap-crossing task, where the animals used a whisker that was spared during the sensory deprivation. Animals that had been sensory deprived performed equally well with the control animals in the gap-crossing task, but were more active in exploring the gap area and consequently made more approaches to the gap - approaches that on average were of shorter duration. A restricted sensory deprivation of only some whiskers, although it does not seem to affect the overall performance of the animals, does have an effect on their behavioral strategy on executing the gap-crossing task.
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Affiliation(s)
- Stylianos Papaioannou
- Department of Neuroscience, Karolinska Institutet, Stockholm Brain Institute Stockholm, Sweden
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Zhang Z, Sun QQ. The balance between excitation and inhibition and functional sensory processing in the somatosensory cortex. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2011; 97:305-33. [PMID: 21708316 DOI: 10.1016/b978-0-12-385198-7.00012-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The balance between excitation and inhibition (E/I balance) is tightly regulated in adult cortices to maintain proper nervous system function. Disturbed E/I balance is associated with numerous neuropsychological disorders, such as autism, epilepsy and schizophrenia. The present review will discuss aspects of Hebbian and homeostatic mechanisms regulating excitatory and inhibitory balance related to sensory processing in somatosensory cortex of rodents. Additionally, changes in the E/I balance during sensory manipulation will be discussed.
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Affiliation(s)
- Zhi Zhang
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
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