Patterns of Local Connectivity in the Neocortex

1993 ◽  
Vol 5 (5) ◽  
pp. 665-680 ◽  
Author(s):  
Andrew Nicoll ◽  
Colin Blakemore
Keyword(s):  
Visual Cortex ◽  
Pyramidal Neurons ◽  
Extreme Values ◽  
Pyramidal Cells ◽  
Excitatory Synapses ◽  
Synaptic Connections ◽  
Local Connectivity ◽  
Connection Probability ◽  
Layer 2 ◽  
Deep Layers

Dual intracellular recording of nearby pairs of pyramidal cells in slices of rat visual cortex has shown that there are significant differences in functional connectivity between the superficial and deep layers (Mason et al. 1991; Nicoll and Blakemore 1993). For pairs of cells no farther than 300 μm apart, synaptic connections between layer 2/3 pyramidal neurons were individually weaker (median peak amplitude, A, of single-fiber excitatory postsynaptic potentials, EPSPs, = 0.4 mV) but more frequent (connection probability, p = 0.087) than those between layer 5 pyramidal neurons (mean A = 0.8 mV, p < 0.015). Taken in combination with plausible estimates of the density of pyramidal cells, the total numbers of synapses on them and the number of synapses formed on their intracortical axons, the present analysis of the above data suggests that roughly 70% of the excitatory synapses on any layer 2/3 pyramid, but fewer than 1% of those on a layer 5 pyramidal neuron, are derived from neighboring pyramidal neurons in its near vicinity. Even assuming very extreme values for some parameters, chosen to erode this difference, the calculated proportion of "local synapses" for layer 5 pyramids was always markedly lower than for layer 2/3 pyramidal neurons. These results imply that local excitatory connections are much more likely to provide significant "intracortical amplification" of afferent signals in layer 2/3 than in layer 5 of rat visual cortex.

Silent Synapses in the Immature Visual Cortex: Layer-Specific Developmental Regulation

2004 ◽  
Vol 91 (2) ◽  
pp. 1097-1101 ◽  
Author(s):  
Simon Rumpel ◽  
Gunnar Kattenstroth ◽  
Kurt Gottmann
Keyword(s):  
Visual Cortex ◽  
Pyramidal Neurons ◽  
Developmental Regulation ◽  
Pyramidal Cells ◽  
Cortical Plate ◽  
Glutamatergic Synapses ◽  
Silent Synapses ◽  
Deep Layers ◽  
Further Development ◽  
Layer Vi

Central glutamatergic synapses are thought to initially form as immature, so-called silent synapses showing exclusively N-methyl-d-aspartate receptor-mediated synaptic transmission. Postsynaptic insertion of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors during further development leads to a conversion into functional, mature synapses. Here, we tested the hypothesis that, according to the “inside first–outside last” pattern of neocortical layer formation and synaptogenesis, pyramidal cells in the superficial layers might show a higher fraction of silent synapses compared with pyramidal cells in the deep layers. We performed an electrophysiological analysis of glutamatergic synapses in acute rat visual cortex slices during postnatal development. In layer VI pyramidal neurons the incidence of silent synapses was high during the first postnatal week and strongly declined during further development. Surprisingly, in superficial cortical plate pyramidal neurons (immature layers II/III), the fraction of silent synapses was initially very low and increased up to the second postnatal week. Thereafter, a similar decline as found in layer VI pyramidal neurons was observed. Thus the developmental regulation of silent synapses was clearly different in pyramidal neurons from different neocortical layers. The almost complete absence of silent synapses at early stages in layer II/III pyramidal neurons indicates that an initially formed subset of synapses is constitutively functional. This might be important to enable spontaneous activity and latter activity-dependent maturation of synapses.

Three-Dimensional Mapping of Unitary Synaptic Connections by Two-Photon Macro Photolysis of Caged Glutamate

2008 ◽  
Vol 99 (3) ◽  
pp. 1535-1544 ◽  
Author(s):  
Masanori Matsuzaki ◽  
Graham C. R. Ellis-Davies ◽  
Haruo Kasai
Keyword(s):  
Visual Cortex ◽  
Single Cell ◽  
Pyramidal Neurons ◽  
Three Dimensional ◽  
Core Region ◽  
Synaptic Connectivity ◽  
Synaptic Connections ◽  
Two Photon ◽  
Layer 2 ◽  
Caged Glutamate

To understand the precise microarchitecture of the cortical circuitry, it is crucial to know the distribution of synaptic connections and their synaptic strengths at the level of a single cell, rather than a group of cells. Here, we describe a new application of two-photon photolysis of caged glutamate that enabled us to induce an action potential in only a small number (about five) of pyramidal neurons by increasing the volume of two-photon excitation by reducing the effective numerical aperture of the objective. We performed whole cell patch-clamp recordings from layer 2/3 pyramidal neurons in the rat visual cortex and stimulated many neurons in a large three-dimensional space (∼600 × 600 × 100 μm) including neurons in layers 2/3 and 4 using this new technique. We mapped the density and amplitude of unitary excitatory postsynaptic currents and found that the basic microarchitecture of excitatory synaptic connections consists of two regions: a columnar, dense core region with a radius of 150 μm and an outer, sparse region. The dense core region includes the majority of strong synaptic connections in layer 2/3. Our results reveal the columnar organization of synaptic connectivity in the rat visual cortex, where functional columns have not been clearly demonstrated. Thus this technique will be a uniquely powerful tool for quantifying synaptic connectivity and manipulating neural activity at the single-cell level.

Silent synapses persist into adulthood in layer 2/3 pyramidal neurons of visual cortex in dark-reared mice

2013 ◽  
Vol 109 (8) ◽  
pp. 2064-2076 ◽  
Author(s):  
Rie Funahashi ◽  
Takuro Maruyama ◽  
Yumiko Yoshimura ◽  
Yukio Komatsu
Keyword(s):  
Visual Cortex ◽  
Ampa Receptors ◽  
Pyramidal Neurons ◽  
Receptor Activation ◽  
Excitatory Synapses ◽  
Brain Functions ◽  
Silent Synapses ◽  
Visual Inputs ◽  
Layer 2 ◽  
Dark Rearing

Immature excitatory synapses often have NMDA receptors but not AMPA receptors in central neurons, including visual cortical pyramidal neurons. These synapses, called silent synapses, are converted to functional synapses with AMPA receptors by NMDA receptor activation during early development. It is likely that this process underlies the activity-dependent refinement of neuronal circuits and brain functions. In the present study, we investigated postnatal development of excitatory synapses, focusing on the role of visual inputs in the conversion of silent to functional synapses in mouse visual cortex. We analyzed presumably unitary excitatory postsynaptic currents (EPSCs) between a pair of layer 2/3 pyramidal neurons, using minimal stimulation with a patch pipette attached to the soma of one of the pair. The proportion of silent synapses was estimated by the difference in the failure rate between AMPA- and NMDA-EPSCs. In normal development, silent synapses were present abundantly before eye opening, decreased considerably by the critical period of ocular dominance plasticity, and almost absent in adulthood. This decline in silent synapses was prevented by dark rearing. The amplitude of presumably unitary AMPA-EPSCs increased with age, but this increase was suppressed by dark rearing. The quantal amplitude of AMPA-EPSCs and paired-pulse ratio of NMDA-EPSCs both remained unchanged during development, independent of visual experience. These results indicate that visual inputs are required for the conversion of silent to functional synapses and this conversion largely contributes to developmental increases in the amplitude of presumably unitary AMPA-EPSCs.

scholarly journals A Quantitative Description of Short-Term Plasticity at Excitatory Synapses in Layer 2/3 of Rat Primary Visual Cortex

1997 ◽  
Vol 17 (20) ◽  
pp. 7926-7940 ◽  
Author(s):  
Juan A. Varela ◽  
Kamal Sen ◽  
Jay Gibson ◽  
Joshua Fost ◽  
L. F. Abbott ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Quantitative Description ◽  
Excitatory Synapses ◽  
Short Term ◽  
Short Term Plasticity ◽  
Layer 2

scholarly journals Asymmetric Temporal Integration of Layer 4 and Layer 2/3 Inputs in Visual Cortex

2011 ◽  
Vol 105 (1) ◽  
pp. 347-355 ◽  
Author(s):  
Giao B. Hang ◽  
Yang Dan
Keyword(s):  
Visual Cortex ◽  
Visual Processing ◽  
Pyramidal Neurons ◽  
Temporal Integration ◽  
Cortical Inhibition ◽  
Multiple Sources ◽  
Layer 2 ◽  
Layer 4 ◽  
The Difference

Neocortical neurons in vivo receive concurrent synaptic inputs from multiple sources, including feedforward, horizontal, and feedback pathways. Layer 2/3 of the visual cortex receives feedforward input from layer 4 and horizontal input from layer 2/3. Firing of the pyramidal neurons, which carries the output to higher cortical areas, depends critically on the interaction of these pathways. Here we examined synaptic integration of inputs from layer 4 and layer 2/3 in rat visual cortical slices. We found that the integration is sublinear and temporally asymmetric, with larger responses if layer 2/3 input preceded layer 4 input. The sublinearity depended on inhibition, and the asymmetry was largely attributable to the difference between the two inhibitory inputs. Interestingly, the asymmetric integration was specific to pyramidal neurons, and it strongly affected their spiking output. Thus via cortical inhibition, the temporal order of activation of layer 2/3 and layer 4 pathways can exert powerful control of cortical output during visual processing.

scholarly journals Developmental Regulation of Basket Interneuron Synapses and Behavior through NCAM in Mouse Prefrontal Cortex

2020 ◽  
Vol 30 (8) ◽  
pp. 4689-4707
Author(s):  
Chelsea S Sullivan ◽  
Vishwa Mohan ◽  
Paul B Manis ◽  
Sheryl S Moy ◽  
Young Truong ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Pyramidal Neurons ◽  
Developmental Regulation ◽  
Brain Slices ◽  
Pyramidal Cells ◽  
Electrophysiological Recording ◽  
Network Function ◽  
Growth Cone Collapse ◽  
Layer 2 ◽  
And Behavior

Abstract Parvalbumin (PV)-expressing basket interneurons in the prefrontal cortex (PFC) regulate pyramidal cell firing, synchrony, and network oscillations. Yet, it is unclear how their perisomatic inputs to pyramidal neurons are integrated into neural circuitry and adjusted postnatally. Neural cell adhesion molecule NCAM is expressed in a variety of cells in the PFC and cooperates with EphrinA/EphAs to regulate inhibitory synapse density. Here, analysis of a novel parvalbumin (PV)-Cre: NCAM F/F mouse mutant revealed that NCAM functions presynaptically in PV+ basket interneurons to regulate postnatal elimination of perisomatic synapses. Mutant mice exhibited an increased density of PV+ perisomatic puncta in PFC layer 2/3, while live imaging in mutant brain slices revealed fewer puncta that were dynamically eliminated. Furthermore, EphrinA5-induced growth cone collapse in PV+ interneurons in culture depended on NCAM expression. Electrophysiological recording from layer 2/3 pyramidal cells in mutant PFC slices showed a slower rise time of inhibitory synaptic currents. PV-Cre: NCAM F/F mice exhibited impairments in working memory and social behavior that may be impacted by altered PFC circuitry. These findings suggest that the density of perisomatic synapses of PV+ basket interneurons is regulated postnatally by NCAM, likely through EphrinA-dependent elimination, which is important for appropriate PFC network function and behavior.

scholarly journals Visual Deprivation Decreases Somatic GAD65 Puncta Number on Layer 2/3 Pyramidal Neurons in Mouse Visual Cortex

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Alicja Kreczko ◽  
Anubhuthi Goel ◽  
Lihua Song ◽  
Hey-Kyoung Lee
Keyword(s):  
Visual Cortex ◽  
Visual Experience ◽  
Pyramidal Neurons ◽  
Immunohistochemical Method ◽  
Inhibitory Synapses ◽  
Acid Decarboxylase ◽  
3D Analysis ◽  
Individual Layer ◽  
Inhibitory Circuitry ◽  
Layer 2

Proper functioning of the visual system depends on maturation of both excitatory and inhibitory synapses within the visual cortex. Considering that perisomatic inhibition is one of the key factors that control the critical period in visual cortex, it is pertinent to understand its regulation by visual experience. To do this, we developed an immunohistochemical method that allows three-dimensional (3D) analysis of the glutamic acid decarboxylase (GAD) 65-positive inhibitory terminals in the visual cortex. Using this method on transgenic mice expressing yellow fluorescence protein (YFP) in a subset of neurons, we found that the number of somatic GAD65-puncta on individual layer 2/3 pyramidal neurons is reduced when mice are dark-reared from birth and reverted to normal levels by re-exposure to light. There was no change in GAD65-puncta volume or intensity. These results support the reorganization of inhibitory circuitry within layer 2/3 of visual cortex in response to changes in visual experience.

Relationship between input connectivity, morphology and orientation tuning of layer 2/3 pyramidal cells in mouse visual cortex

2020 ◽  
Author(s):  
Simon Weiler ◽  
Drago Guggiana Nilo ◽  
Tobias Bonhoeffer ◽  
Mark Hübener ◽  
Tobias Rose ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Synaptic Input ◽  
Pyramidal Cells ◽  
Excitatory Input ◽  
Orientation Tuning ◽  
Inhibitory Input ◽  
Layer 2 ◽  
Dendritic Complexity ◽  
Inhibitory Synaptic Input

AbstractNeocortical pyramidal cells (PCs) display functional specializations defined by their excitatory and inhibitory circuit connectivity. For layer 2/3 (L2/3) PCs, little is known about the detailed relationship between their neuronal response properties, dendritic structure and their underlying circuit connectivity at the level of single cells. Here, we ask whether L2/3 PCs in mouse primary visual cortex (V1) differ in their functional intra- and interlaminar connectivity patterns, and how this relates to differences in visual response properties. Using a combined approach, we first characterized the orientation and direction tuning of individual L2/3 PCs with in vivo 2-photon calcium imaging. Subsequently, we performed excitatory and inhibitory synaptic input mapping of the same L2/3 PCs in brain slices using laser scanning photostimulation (LSPS).Our data from this structure-connectivity-function analysis show that the sources of excitatory and inhibitory synaptic input are different in their laminar origin and horizontal location with respect to cell position: On average, L2/3 PCs receive more inhibition than excitation from within L2/3, whereas excitation dominates input from L4 and L5. Horizontally, inhibitory input originates from locations closer to the horizontal position of the soma, while excitatory input arises from more distant locations in L4 and L5. In L2/3, the excitatory and inhibitory inputs spatially overlap on average. Importantly, at the level of individual neurons, PCs receive inputs from presynaptic cells located spatially offset, vertically and horizontally, relative to the soma. These input offsets show a systematic correlation with the preferred orientation of the postsynaptic L2/3 PC in vivo. Unexpectedly, this correlation is higher for inhibitory input offsets within L2/3 than for excitatory input offsets. When relating the dendritic complexity of L2/3 PCs to their orientation tuning, we find that sharply tuned cells have a less complex apical tree compared to broadly tuned cells. These results indicate that the spatial input offsets of the functional input connectivity are linked to orientation preference, while the orientation selectivity of L2/3 PCs is more related to the dendritic complexity.

Layer-specific involvement of endocannabinoid signaling in muscarinic-induced long-term depression in layer 2/3 pyramidal neurons of rat visual cortex

2019 ◽  
Vol 1712 ◽  
pp. 124-131 ◽  
Author(s):  
Kayoung Joo ◽  
Kwang-Hyun Cho ◽  
Sung-Hee Youn ◽  
Hyun-Jong Jang ◽  
Duck-Joo Rhie
Keyword(s):  
Visual Cortex ◽  
Pyramidal Neurons ◽  
Long Term Depression ◽  
Layer 2
Sign in / Sign up

Export Citation Format

Share Document