Functional Organization and Development of Connectivity in L2/3 of Mouse Primary Visual Cortex PDF Download
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Author: Lee Cossell
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Languages : en
Pages : 0
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Author: Lee Cossell
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Languages : en
Pages : 0
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Author:
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Languages : en
Pages : 282
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Author: Marley Rossa
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Languages : en
Pages : 0
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A distinguishing feature of the mammalian cerebral cortex is its laminar architecture, each layer containing a unique composition of neuronal types with distinct morphologies, molecular markers, and electrophysiological properties. These neurons form precise, specific synaptic connections with one another to form complex microcircuits that underlie sensory information processing. By compartmentalizing computation into layers, the cortex can efficiently channel and transform information to represent and interact with the external world. Therefore, deciphering the precise input and output connectivity structure of different neuronal types in the context of their respective layers is necessary to fully appreciate their unique functional roles in the representation and manipulation of sensory information. This dissertation builds on the traditional idea of a canonical interlaminar circuit by characterizing fundamental intracortical connections between excitatory and inhibitory cell types. Chapter 1 explores the relative functional input distributions from 5 layer-specific excitatory subpopulations to 4 cell types in mouse primary visual cortex (V1). By optogenetically activating these excitatory subpopulations and recording from targeted excitatory and inhibitory subtypes across cortical layers 2/3-6, I elucidate a complex interlaminar network that provides a novel framework for visual information processing. In Chapter 2, I approach the interlaminar connectivity of mouse V1 from a transcriptomic perspective using our newly developed method Single Transcriptome Assisted Rabies Tracing (START). By combining rabies tracing using glycoprotein (G)-deleted rabies virus (RVdG) with snRNAseq, we identify, and transcriptomic ally characterize cells projecting to the same layer-specific subpopulations as in Chapter 1. We find that START generates results consistent with established circuit models validating the utility of START as a circuit tracing tool. More importantly, with the increased cell type granularity achieved with transcriptomic characterization of inputs, we were able to uncover specific subtypes of somatostatin and parvalbumin interneurons that provide input to excitatory cells across layers. Taken together, findings from Chapters 1 and 2 demonstrate layer and cell type specificity in cortical circuit structure, indicating that a cell's laminar position and synaptic connectivity are deeply intertwined with its functional role. Understanding cell type diversity in the context of circuit architecture forms the foundation of a novel framework for cortical information processing.
Author: Jami Lynn Milton
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Languages : en
Pages : 342
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Author: Marta Gajowa
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Languages : en
Pages : 0
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Feature selectivity of cortical neurons, one example of functional properties in the brain, is the ability of neurons to respond to particular stimulus attributes - e.g. the receptive field of a neuron in the primary visual cortex (V1) with respect to object movement direction. This thesis contributes to understanding how feature selectivity arises in mouse V1. It is divided into two parts, each based on distinct approaches to elucidate visual processing mechanisms, the first at a population level and the second at the single neuron level. First, on a population level, I have developed tools towards an eventual project that combines 2-photon optogenetics, 2-photon imaging and traditional whole-cell electrophysiology to map functional connectivity in V1. This map will provide a link between cell tuning (i.e. cell function) and network architecture, enabling quantitative and qualitative distinction between two extreme scenarios in which cells in mouse V1 are either randomly connected, or are associated in specialized subnetworks. Here I describe the technical validation of the method, with the main focus on finding the appropriate biological preparation and reagents. Second, based on whole-cell patch recordings of single mouse V1 neurons in vivo, I characterize the neuronal input-output (I/O) transfer function using current and conductance inputs, the latter intended to mimic the biophysical properties of synapses in a functional context. I employ a novel closed-loop in vivo protocol based on a combination of current, voltage and dynamic clamp recording modes. I first measure the basic I/O transfer function of a given neuron with current and conductance steps, under current and dynamic clamp, respectively. I then measure the visually evoked spiking output, under current clamp, and the synaptic conductance input, under voltage clamp, to that neuron. Finally, I reintroduce variations of the visually-evoked conductance input to the same cell under dynamic clamp. In that manner, I describe an I/O transfer function which allows a characterization of the mathematical operations performed by the neuron during functional processing. Furthermore, modifications of the relative scaling and the temporal characteristics of the excitatory and inhibitory components of the reintroduced synaptic input, enables dissection of each component's role in shaping the spiking output, as well as to infer overall differences between various physiological cell types (e.g. regular-adapting, presumably excitatory, versus fast-spiking, presumably inhibitory, neurons). Finally, examination of the transfer functions, in particular their dependence on temporal modifications, provides insights on the relationship between the neuronal code and the biophysical properties of neurons and their network.
Author: Nicholas David Olivas
Publisher:
ISBN: 9781303117213
Category :
Languages : en
Pages : 158
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The structure of neuronal circuitry in primary visual cortex (V1) is sculpted by the occurrence of three distinct events: spontaneous retinal waves in early postnatal life, visual experience following eye opening, and the critical period during adolescence. Following the critical period, visual responses measured in cortex remain stable - suggesting a permanent maturation of cortical circuits that last a lifetime. Primary visual cortex is comprised of 6 radially stacked layers that respond to visual input from lateral geniculate nucleus (LGN) and subsequently relays information to extrastriate areas to engage higher visual processes. Despite known fundamental principles cortical organization, missing is a detailed understanding of the connectivity between specific neuronal types across V1 layers and the changes in connectivity accompanying cortical maturation. In this dissertation, we provide new insight into the laminar organization and response properties of excitatory and inhibitory neurons in local V1 circuits following eye opening and during the critical period. The studies described here use innovative optical and genetic tools to selectively turn on and silence activity in specific groups of neurons in V1. Single cell patch clamp recordings combined with glutamate uncaging and laser scanning photostimulation (LSPS) enabled comprehensive mapping of the spatial distribution and strength of synaptic connectivity in precise V1 circuits during distinct phases of V1 development. In the introduction, we present a general overview of V1 anatomy and the dominant cell types facilitating visual processing in V1 circuits. Chapters 1-3 investigate V1 circuitry days after eye opening but prior to the onset of the critical period. In Chapter 1, we review recent technical development in our laboratory used to provide the first account of functional connectivity between interconnected layers in mouse V1. In Chapter 2, we demonstrate how discrete layers in V1 interact when simultaneously activated and reveal temporally sensitive increases in local inhibition contributed by Parvalbumin (PV) expressing inhibitory neurons which constrain the flow of excitatory information in local V1 circuits. Chapter 3 presents extensive mapping data of aggregate excitatory and inhibitory inputs made to individual pyramidal cells in layers 2/3, 4, 5a, 5b, and 6 in V1. Our results demonstrate that days following eye opening, the distribution of excitatory and inhibitory inputs to pyramidal cells is spatially coupled across layers. In Chapter 4, we provide the first account of cell type specific changes initiating ocular dominance plasticity in V1 during the critical period in awake mice in vivo and by using local circuit analyses in vitro. We show that brief 24 hour monocular deprivation during the critical period (cMD) results in a dramatic decrease of visually evoked responses in L2/3 PV cells and an increase in activity in L2/3 pyramidal cells in vivo. In vitro local circuit mapping revealed that these cell type specific changes to visual stimuli are caused by a weakening of L4 and L5a excitatory inputs onto L2/3 PV cells but not L2/3 pyramidal cells following brief monocular deprivation.
Author: Pasko Rakic
Publisher: Academic Press
ISBN: 0128236736
Category : Psychology
Languages : en
Pages : 560
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Synapse Development and Maturation, the latest release in the Comprehensive Developmental Neuroscience series, presents the latest information on the genetic, molecular and cellular mechanisms of neural development. The book provides a much-needed update that underscores the latest research in this rapidly evolving field, with new section editors discussing the technological advances that are enabling the pursuit of new research on brain development. This volume focuses on the synaptogenesis and developmental sequences in the maturation of intrinsic and synapse-driven patterns. Features leading experts in various subfields as section editors and article authors Presents articles that have been peer reviewed to ensure accuracy, thoroughness and scholarship Includes coverage of mechanisms which regulate synapse formation and maintenance during development Covers neural activity, from cell-intrinsic maturation, to early correlated patterns of activity
Author: Adrian K. Andelin
Publisher:
ISBN:
Category :
Languages : en
Pages : 158
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Despite the fact that the visual system has been the most well-studied of all sensory systems, many questions remain in regard to its structure and function in both human and animal models. While a basic blueprint of the visual system exists across all animal species that sets in place the basic structure prior to the onset of visual experience, it has been well established that this system becomes fine-tuned through experience early in life. Using a variety of techniques and animal models, this dissertation addresses some questions regarding the functional organization and the effect of visual deprivation on the visual cortex of several animal models. Rodents offer several advantages for studying various aspects of the development, organization and plasticity of the visual system. An important model for studies of visual cortex plasticity is the system of ocular dominance columns (ODC, aggregates of cells with the same eye preference), which have been extensively studied in many carnivores and primates, but have been thought not to exist in rodents. Our lab recently reported the existence of ODCs in pigmented, Long Evans rats (Laing et al. 2015), but previous reports in albino rats (Diao et al., 1983) point to differences in the binocularity of certain regions of primary visual cortex (V1) and in the role that callosal connections may have in these differences. To explain these strain differences, we hypothesized that albino rats, unlike Long Evans rats, do not have ODCs, and that callosal connections in V1 of albino rats are not patchy, as they are in Long Evans rats. In the first chapter of this dissertation, we present anatomical and electrophysiological experiments supporting our prediction that input from both eyes intermix in the binocular region of V1 in albino rats, without segregating into ODCs, and that callosal connections in albino rats are homogeneously distributed in V1. In the second chapter, we explore the effect of loss of vision during early development on the surface area of V1. Using histological methods as well as MRI techniques, we examined how the reduction in mature brain surface area varies with age when blindness occurs in rats, ferrets and humans. To compare data across species, we translated the post-conception ages of each species to a common neurodevelopmental event-time scale. We predicted that the critical period for the effect of blindness on the area of V1 ends at a common developmental event-time across species. Our results support our prediction, and also show that the critical period for the effect of blindness on V1 surface area ends well before the visual cortex reaches its normal, mature size. Much of the research on the organization and function of visual cortex is presently carried out in mice. While a present advantage of mice is the possibility of using genetic tools, a disadvantage is the small size of their brain and visual cortex. In the third chapter, we use multiple anatomical tracers to explore the number, arrangement and internal topographic organization of extrastriate visual areas in the rabbit, whose brain is about 60 times larger than the mouse brain. Our results show that the visual cortical plan in rabbits closely resembles the plan in mice and rats, suggesting that the rodent plan may be more general, encompassing Lagomorphs and possibly other orders. Our study also underscores the usefulness of the rabbit as an alternative model to rats and mice for projects benefiting from a larger brain.
Author: Jing Ning
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Languages : en
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"Laminar structure is a distinctive feature of cerebral cortex which comprises 6 layers, in which each layer is characterized by distinct cellular organization, specific inputs and projection targets. Anatomical circuitry across laminae has been well-studied, and previous studies have shown laminar-dependence of neural responses, suggesting that sensory information is processed in a laminar-dependent manner. However, the functional circuitry across laminae related to the underlying mechanism of laminar processing remains largely unexplored. This project is to explore functional connectivity measured with spiking activity across laminae, and test the hypothesis that functional connections triggered by first-order stimuli and second-order stimuli share great similarity. Here, by using a series of functional connectivity methods, we investigate association and causal relationship across laminae in primary visual cortex. While responding to visual stimuli, neurons across cortical depth in A17 of the anesthetized and paralyzed cats were recorded with a 32-channel linear array probes (NeuroNexus). Current source density (CSD) analysis was applied to low frequency components of sinewave grating responses, to approximately localize recording sites into 3 layers: (supra-granular (SG), granular (G), and infra-granular (IG)) (Nicholson & Freeman, 1975; Mitzdorf & Singer, 1978). Multiunit activity (MUA) was extracted from recorded neuronal responses for each channel, as times of level-crossings at 3 standard deviations of the bandpass digitally filtered (300 Hz - 3.0 kHz) signal. We implemented a series of functional connectivity methods in Matlab, including mutual information, Pearson correlation, Granger causality (GC) and conditional Granger causality to measure neural interactions between cortical layers with multiunit spiking activityMUA (MUA) data. Analysis of conditional Granger causality could remove variance explained by other variables when estimating pairwise functional connectivity. Here we used a nonparametric version of Granger causality analysis, designed to handle spiking responses (Y. Chen, Bressler, & Ding, 2006; Dhamala, Rangarajan, & Ding, 2008; Hirabayashi, Takeuchi, Tamura, & Miyashita, 2013; R. Chen, Wang, Liang, & Li, 2017a). For validation, we tested these methods on simulated spiking data from a small network of leaky integrate-and-fire models. Then we analyzed datasets triggered by both luminance-modulated (LM) static gratings and contrast-modulated (CM) static gratings and compared the patterns of functional connectivity. These methods showed patterns of functional connectivity across laminae, exhibiting a similar relation to the laminar structure measured by CSD. The causal influences between cortical layers, as measured by GC and conditional GC, are predominantly in the direction from the G layer to SG layers, from the SG and G layers to the IG layerAnalysis of GC and conditional GC indicated directionality of connections. The results of these two methods also suggests that inter-laminar connections were greatly strengthened by responses within intra-laminar connections. In conclusion, these three functional connectivity measures, including mutual information, Pearson correlation and Granger causality, suggest how neurons in the primary visual cortex process sensory inputs in a laminar-dependent manner. Functional connectivity triggered by first-order stimuli and second-order stimuli shares great similarity in pattern of directional biases, consistent with shared processing mechanisms for these two kinds of stimuli, though with some differences in strength of connections"--
Author: Alessandro Roberto Galloni
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Languages : en
Pages : 0
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A central question in neuroscience is how expectations shape sensory processing. In the cerebral cortex, feedforward connections convey sensory information, while feedback connections are thought to be crucial for directing attention, signaling contextual information, and enabling perceptual inference. Thick-tufted layer 5 (ttL5) pyramidal neurons play an important role in integrating sensory, internal, and motor information. They have large complex morphologies that receive thousands of synaptic inputs from across the brain, and express a diverse set of active conductances which support highly nonlinear dendritic computations. Their axons also form the largest output pathway from the cerebral cortex, making them ideally positioned to integrate and summarise cortical computations to drive behaviour. In this thesis, I perform whole-cell patch clamp recordings to characterize the intrinsic properties of a population of ttL5 neurons in the medial secondary visual cortex (V2m) of mice, genetically labelled in the Glt25d2-Cre line. These neurons are found to form a homogeneous population with integrative properties that are broadly consistent with several known features of ttL5 neurons. The inputs to Glt25d2-Cre neurons in V2m are found to originate in several brain regions, associated with both sensory and internal representations. Using optogenetics and spatially patterned optical stimulation, I map the spatial distributions of synapses from these regions on the dendritic trees of the ttL5 neurons. These inputs target distinct dendritic domains in a pattern that argues against classical notions of hierarchical connectivity. By electrically stimulating the largest input populations, I show that these pathways display synaptic facilitation and sum linearly across a wide range of temporal intervals. Furthermore, I find that Ca(2+)-mediated supralinearities, such as backpropagation-activated spike bursts, which have been extensively described in primary visual and somatosensory cortex, are absent in V2m neurons. Finally, through a combination of electrophysiological recordings, morphological reconstructions, and computational modelling, I show that dendritic excitability in ttL5 neurons is modulated by apical trunk length. In summary, I thoroughly describe the properties of a new ttL5-specific mouse line and provide new evidence that ttL5 neuron properties and canonical notions of hierarchical connectivity are not universally applicable throughout the cortex.
