Efficient Recruitment of Layer 2/3 Interneurons by Layer 4 Input in Single Columns of Rat Somatosensory Cortex

Helmstaedter, Moritz; Staiger, Jochen F.; Sakmann, Bert; Feldmeyer, Dirk

doi:10.1523/jneurosci.5701-07.2008

Cited by 107 publications

(120 citation statements)

References 66 publications

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“…inhibitory (FS and low-threshold spiking inhibitory cell) connections (65) in cortical layer 4 (L4) of rodent barrel cortex; 0.45 (n = 146) in auditory cortex (66) and 0.59 (n = 79) in visual and somatosensory cortices (29) for excitatory to inhibitory (FS) projections in rodent L2/3; 0.43 (n = 26) for pyramidal to Martinotti connections in L5 of rat somatosensory cortex (67); 0.21 (n = 22) for pyramidal to inhibitory connections in L2/3 of rat somatosensory, motor, and visual cortices (68); 0.88 (n = 36) for excitatory to inhibitory (FS) connections in L2/3 of mouse V1 (69); and 0.76 (n = 28) for L4 spiny stellate to L2/3 inhibitory cell connections in rat barrel cortex (70). The last two of these projections deviate significantly from the predictions of the model, indicating that either these projections are not directly involved in efficient associative memory storage or the model assumptions must be revised to extend the theory on these classes of postsynaptic inhibitory cells.…”

Section: Discussionmentioning

confidence: 99%

Efficient associative memory storage in cortical circuits of inhibitory and excitatory neurons

Chapeton

Fares

LaSota

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Many features of synaptic connectivity are ubiquitous among cortical systems. Cortical networks are dominated by excitatory neurons and synapses, are sparsely connected, and function with stereotypically distributed connection weights. We show that these basic structural and functional features of synaptic connectivity arise readily from the requirement of efficient associative memory storage. Our theory makes two fundamental predictions. First, we predict that, despite a large number of neuron classes, functional connections between potentially connected cells must be realized with <50% probability if the presynaptic cell is excitatory and >50% probability if the presynaptic cell is inhibitory. Second, we establish a unique relation between probability of connection and coefficient of variation in connection weights. These predictions are consistent with a dataset of 74 published experiments reporting connection probabilities and distributions of postsynaptic potential amplitudes in various cortical systems. What is more, our theory explains the shapes of the distributions obtained in these experiments.learning and memory | cortical connectivity | synaptic weight | perceptron | critical capacity F undamental functions of the brain, such as learning and memory storage, are mediated by many mechanisms of excitatory (1-4) and inhibitory (5-9) synaptic plasticity. Working together with the genetically encoded developmental mechanisms of circuit formation, synaptic plasticity shapes neural circuits by creating, modifying, and eliminating individual synaptic connections in an experience-dependent manner. It is, therefore, reasonable to hypothesize that many stereotypic features of adult synaptic connectivity, whether established through evolution or the developmental learning process, have arisen to facilitate memory storage.In this study, we focus on three such features of cortical connectivity. Cortical connectivity is predominantly excitatory; it is mediated by two major classes of neurons-excitatory glutamatergic and inhibitory GABAergic cells. Chemical synapses made by the axons of inhibitory cells in the adult brain are believed to be all inhibitory, whereas those synapses made by the axons of excitatory neurons are believed to be all excitatory (10). The resulting connectivity is largely excitatory, with only about 15-20% of inhibitory neurons and inhibitory synapses (11). The second stereotypic feature of cortical connectivity is sparseness. Networks in the cortex are thought to be organized into relatively small units ranging from hundreds to tens of thousands of neurons in size. Such units may include mini columns (12, 13), structural columns (14, 15), and a variety of functional columns (16,17). Analysis of neuron morphology (14,(18)(19)(20)(21) has shown that cells within such units have the potential of being connected by structural synaptic plasticity (22-24). However, despite this potential, synaptic connectivity within the units is sparse. For example, nearby excitatory neurons in the neocortex are sy...

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Section: Discussionmentioning

confidence: 99%

Efficient associative memory storage in cortical circuits of inhibitory and excitatory neurons

Chapeton

Fares

LaSota

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…To build detailed mechanistic models of cortical function (50), single cells representative of distinct anatomically and functionally defined groups of excitatory and inhibitory neurons have to be placed throughout the layers of a cortical column at sufficient spatial precision and in the correct quantity. The data on the number of inhibitory neurons within the layers of a barrel column reported here, together with data on innervation probabilities and axonal projection patterns (10,58,59), will serve as a basis for reconstructing the inhibitory synaptic circuits within and between cortical columns.…”

Section: Molecular Markers Of Ins In a Corticalmentioning

confidence: 99%

“…13, [16][17][18]]. However, because of the lack of clearly distinguishing anatomical features under most experimental conditions, L2 and L3 were treated as one layer (L2/3) in most physiological studies (e.g., 8,10,11,[42][43][44][45]. Recently, evidence for functional differences in electrical activity between L2 and L3 has accumulated from different cortical areas, such as somatosensory barrel cortex (2,46,47) and visual cortex (48).…”

Section: Molecular Markers Of Ins In a Corticalmentioning

confidence: 99%

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Inhibitory interneurons in a cortical column form hot zones of inhibition in layers 2 and 5A

Meyer

Schwarz

Wimmer

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

208

170

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Although physiological data on microcircuits involving a few inhibitory neurons in the mammalian cerebral cortex are available, data on the quantitative relation between inhibition and excitation in cortical circuits involving thousands of neurons are largely missing. Because the distribution of neurons is very inhomogeneous in the cerebral cortex, it is critical to map all neurons in a given volume rather than to rely on sparse sampling methods. Here, we report the comprehensive mapping of interneurons (INs) in cortical columns of rat somatosensory cortex, immunolabeled for neuron-specific nuclear protein and glutamate decarboxylase. We found that a column contains ∼2,200 INs (11.5% of ∼19,000 neurons), almost a factor of 2 less than previously estimated. The density of GABAergic neurons was inhomogeneous between layers, with peaks in the upper third of L2/3 and in L5A. IN density therefore defines a distinct layer 2 in the sensory neocortex. In addition, immunohistochemical markers of IN subtypes were layer-specific. The "hot zones" of inhibition in L2 and L5A match the reported low stimulus-evoked spiking rates of excitatory neurons in these layers, suggesting that these inhibitory hot zones substantially suppress activity in the neocortex.F or a quantitative understanding of the interaction between excitatory and inhibitory synaptic transmission in the neocortex, it is crucial to obtain data on the absolute numbers and the relative distribution of excitatory and inhibitory (mostly GABAergic) neurons [interneurons (INs)] in a cortical column. Only on the basis of such prevalence numbers is it possible to interpret data on single-cell physiology (1-8) and synaptic connections of pairs of neurons (9-12) at the circuit level. The distribution of cortical neurons and INs has therefore been the objective of several studies over the past decades (13-15). Statistical sampling methods were used because mapping tens of thousands of neurons was not feasible. Although the nominal error bounds of such methods are in the range of 10-20%, the reported absolute numbers differed strongly among studies, especially for sparse neuron populations, such as INs and their subtypes. The ratio of INs reported for the somatosensory cortex varied between 15% and 25%, thus by almost a factor of 2 (13,16,17). Data on possible differences in IN density between layers in a cortical column were contradictory (13,15,16,18,19).To resolve these substantial discrepancies, we undertook the complete mapping of INs in entire cortical columns using the cytoarchitectonic barrels in L4 as a reference frame for the thalamocortical innervation volume (20) in postnatal day (P) 25-36 rat vibrissal cortex. Our data show that the overall prevalence of inhibitory neurons was previously overestimated by almost a factor of 2. We find a unique substructure of the distribution of INs in a cortical column that can explain the layer-specific differences in the excitability in neocortex. The distribution of INs defines layer 2 as a distinct neocortical layer.

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“…Patkány szomatoszenzoros kérgi piramissejtek 1-4 szinapszist létesítettek kosársejteken és más interneuronokon (Tamas et al, 2002;Wang et al, 2002). Patkány szomatoszenzoros és szomatomotoros kérgi területein végzett további vizsgálatok is hasonlóan alacsony szinapszis számokról számoltak be glutamáterg sejtek és interneuronok közötti kapcsolatokban (Deuchars and Thomson, 1995;Helmstaedter et al, 2008). A fenti tanulmányokban vizsgált piramissejt-interneuron kapcsolatok EPSP amplitúdói mindössze 0,5 mV -3 mV körüliek voltak, szemben az általunk hasonló szinapszis számok mellett tapasztalt 6,6 mV -11,2 mV-os EPSP-k amplitúdóival, ami azt mutatja, hogy az egyedi szinapszisok szintjén érdemes keresni a humánban tapasztalt megerősödött szinaptikus transzmisszió okát.…”

Section: Egy Sejt áLtal Aktivált Poliszinaptikus Hálózatok a Humány Aunclassified

Humán agykérgi neuronhálózatok működése és szerotonerg szabályozása

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Efficient Recruitment of Layer 2/3 Interneurons by Layer 4 Input in Single Columns of Rat Somatosensory Cortex

Cited by 107 publications

References 66 publications

Efficient associative memory storage in cortical circuits of inhibitory and excitatory neurons

Efficient associative memory storage in cortical circuits of inhibitory and excitatory neurons

Inhibitory interneurons in a cortical column form hot zones of inhibition in layers 2 and 5A

Humán agykérgi neuronhálózatok működése és szerotonerg szabályozása

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