scholarly journals Visual Spatial Characterization of Macaque V1 Neurons

2001 ◽  
Vol 85 (5) ◽  
pp. 1873-1887 ◽  
Author(s):  
Michael P. Sceniak ◽  
Michael J. Hawken ◽  
Robert Shapley
Keyword(s):  
Spatial Organization ◽  
Spatial Summation ◽  
Surround Suppression ◽  
Visual Responses ◽  
V1 Neurons ◽  
Spatial Characterization ◽  
Difference Of Gaussians ◽  
Visual Spatial ◽  
Dog Model

This study characterizes the spatial organization of excitation and inhibition that influences the visual responses of neurons in macaque monkey's primary visual cortex (V1). To understand the spatial extent of excitatory and inhibitory influences on V1 neurons, we performed area-summation experiments with suprathreshold contrast stimulation. The extent of spatial summation and the magnitude of surround suppression were estimated quantitatively by analyzing the spatial summation experiments with a difference of Gaussians (DOG) model. The average extent of spatial summation is approximately the same across layers except for layer 6 cells, which tend to sum more extensively than cells in the other layers. On average, the extent of length and width summation is approximately equal. Across the population, surround suppression is greatest in layer 4B and weakest in layer 6. Estimates of summation and suppression are compared for the DOG (subtractive) model and a normalization (divisive) model. The two models yield quantitatively similar estimates of the extent of excitation and inhibition. However, the normalization (divisive) model predicts weaker surround strength than the DOG model.

scholarly journals Visual Spatial Summation in Macaque Geniculocortical Afferents

2006 ◽  
Vol 96 (6) ◽  
pp. 3474-3484 ◽  
Author(s):  
Michael P. Sceniak ◽  
Soumya Chatterjee ◽  
Edward M. Callaway
Keyword(s):  
Spatial Summation ◽  
Afferent Input ◽  
Visual Signals ◽  
Spatial Extent ◽  
Visual Response ◽  
Surround Suppression ◽  
Spatial Spread ◽  
Cortical Input ◽  
Visual Spatial ◽  
Spread Of Excitation

The spatial summation properties of visual signals were analyzed for geniculocortical afferents in the primary visual cortex (V1) of anesthetized paralyzed macaque monkeys. Afferent input responses were recorded extracellularly during cortical inactivation through superfusion of the cortex with muscimol, allowing investigation of lateral geniculate nucleus of the thalamus (LGN) cell properties in the absence of cortical feedback. Responses from afferent inputs were classified as magno-, parvo-, or koniocellular based on anatomical organization within the cortex, established through histological reconstructions, and visual response wavelength sensitivity. More than 80% of afferents showed strong surround suppression [suppression index (SI) >0.5] and 14% showed negligible surround suppression (SI < 0.2). Afferent responses with weak and strong surround suppression were found throughout cortical input layers 4C and 4A. High-contrast estimates of the spatial extent of the classical surround were similar to the nonclassical surround. The classical and nonclassical surrounds were, on average, 1.5-fold larger than the excitatory center. Unlike neurons within V1, the spatial extent of excitatory summation for geniculocortical afferents was contrast invariant. Nonclassical surround suppression showed slight contrast dependency with estimates larger (20%) at lower contrasts and stronger at higher contrasts (13%). Surround suppression is inherent in cortical input responses and likely derives from lateral inhibition in either the LGN or retina. Although surround suppression within afferent responses increases slightly with contrast, the spatial spread of excitation remains fixed with contrast. This argues for distinct mechanisms of action for contrast-dependent modulation in cortical and subcortical responses.

scholarly journals ECOA-5. Integrative 3D spatial characterization of genomic and epigenomic intratumoral heterogeneity in glioblastoma

2021 ◽  
Vol 3 (Supplement_2) ◽  
pp. ii2-ii2
Author(s):  
Radhika Mathur ◽  
Qixuan Wang ◽  
Patrick Schupp ◽  
Stephanie Hilz ◽  
Chibo Hong ◽  
...  
Keyword(s):  
Rna Sequencing ◽  
Spatial Organization ◽  
Three Dimensional ◽  
Spatial Location ◽  
Cell Types ◽  
Intratumoral Heterogeneity ◽  
Tumor Evolution ◽  
Open Chromatin ◽  
Spatial Characterization

Abstract Treatment failure in glioblastoma is often attributed to intratumoral heterogeneity (ITH), which fosters tumor evolution and selection of therapy-resistant clones. While genomic alterations are known contributors to ITH, emerging studies highlight functional roles for epigenomic ITH which integrates differentiation status, stochastic events, and microenvironmental inputs. Here, we have established a novel platform for integrative characterization of genomic and epigenomic ITH of glioblastoma in three-dimensional (3-D) space. In collaboration with neurosurgeons and biomedical imaging experts, we utilize 3-D surgical neuro-navigation to safely acquire ~10 tumor samples per patient representing maximal anatomical diversity. We conduct whole-exome sequencing, RNA sequencing, and assay for transposase-accessible chromatin using sequencing (ATAC-Seq) on each sample. The spatial location of each sample is mapped by its 3-D coordinates, allowing 360-degree visualization of genomic and epigenomic ITH for each patient. We demonstrate this approach on 8 patients with primary IDH-WT glioblastoma (83 spatially mapped samples), providing unprecedented insight into their spatial organization at the genomic and epigenomic levels. We link genetically defined tumor subclones to patterns of open chromatin and gene regulation, revealing underlying transcription factor binding at active promoters and enhancers. We also identify ITH in whole-genome doubling and focal oncogene amplification events in multiple patients, which we then link with epigenomic ITH. Further, to study microenvironmental inputs and their contribution to epigenomic ITH, we conduct deconvolution of RNA sequencing and ATAC-Seq data by analyzing feature co-variation. We resolve the 3-D spatial organization of immune, neural, and other nontumor cell types present in glioblastoma, characterizing their functional states and interactions with tumor cells. This work provides the most comprehensive spatial characterization of genomic and epigenomic ITH to date in glioblastoma. As a resource for further investigation, we have developed an interactive data sharing platform – The 3D Glioma Atlas – that enables 360-degree visualization of both genomic and epigenomic ITH.

scholarly journals Surround Suppression in Primate V1

2001 ◽  
Vol 86 (4) ◽  
pp. 2011-2028 ◽  
Author(s):  
H. E. Jones ◽  
K. L. Grieve ◽  
W. Wang ◽  
A. M. Sillito
Keyword(s):  
Spatial Organization ◽  
Moving Objects ◽  
Three Dimensional ◽  
Spatial Summation ◽  
Visual Space ◽  
Detailed Examination ◽  
Dimensional Structure ◽  
Reverse Direction ◽  
Surround Suppression ◽  
Motion Contrast

We investigated the spatial organization of surround suppression in primate primary visual cortex (V1). We utilized drifting stimuli, configured to extend either from within the classical receptive field (CRF) to surrounding visual space, or from surrounding visual space into the CRF or subdivided to generate direction contrast, to make a detailed examination of the strength, spatial organization, direction dependence, mechanisms, and laminar distribution of surround suppression. Most cells (99/105, 94%) through all cortical layers, exhibited suppression (mean reduction 67%) to uniform stimuli exceeding the CRF, and 43% exhibited a more than 70% reduction. Testing with an annulus revealed two different patterns of surround influence. Some cells (37% of cells), classical surround suppression (CSS) cells exhibited responses to an annulus encroaching on the CRF that were less than the plateau in the spatial summation curve. The majority (63%), center-gated surround suppression (CGSS) cells, showed responses to annuli that equaled or exceeded the plateau in the spatial summation curve. Analysis suggested the CSS mechanism was implemented in all cells while the CGSS mechanism was implemented in varying strength across the sample with the extreme reflected in cells that gave larger responses to annuli than to a center stimulus. Reversing the direction of motion of the portion of the stimulus surrounding the CRF revealed four different patterns of effect: no reduction in the degree of suppression (22% of cells), a reduction in surround suppression (41%), a facilitation of the response above the level to the inner stimulus alone (37%), and a facilitation of the response above that to the inner stimulus alone that also exceeded the values associated with an optimal inner stimulus. The facilitatory effects were only seen for reverse direction interfaces between the central and surrounding stimulus at diameters equal to or more than the CRF size. The zones driving the suppressive influences and the direction contrast facilitation were often spatially heterogeneous and for a number of cells bore strong comparison with the class of behavior reported for surround mechanisms in MT. This suggests a potential role, for example, in extracting information about motion contrast in the representation of the three dimensional structure of moving objects.

scholarly journals Fast camera spatial characterization of photonic polarization entanglement

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Christopher Ianzano ◽  
Peter Svihra ◽  
Mael Flament ◽  
Andrew Hardy ◽  
Guodong Cui ◽  
...  
Keyword(s):  
Spatial Characterization

scholarly journals Visualization and Temporal/Spatial Characterization of Cardiac Radiofrequency Ablation Lesions Using Magnetic Resonance Imaging

Circulation ◽  
2000 ◽  
Vol 102 (6) ◽  
pp. 698-705 ◽  
Author(s):  
Albert C. Lardo ◽  
Elliot R. McVeigh ◽  
Pitayadet Jumrussirikul ◽  
Ronald D. Berger ◽  
Hugh Calkins ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Radiofrequency Ablation ◽  
Magnetic Resonance ◽  
Resonance Imaging ◽  
Spatial Characterization

The Membrane Skeleton of Pseudomicrothorax

1991 ◽  
Vol 100 (4) ◽  
pp. 707-715 ◽  
Author(s):  
IRM HUTTENLAUCH ◽  
ROBERT K. PECK
Keyword(s):  
Spatial Organization ◽  
Membrane Skeleton ◽  
Basal Bodies ◽  
Structural Elements ◽  
Or Groups ◽  
Positive Immunoreactivity ◽  
Cortical Membranes ◽  
Cytoskeletal Elements

The membrane skeleton, or epiplasm, is part of the structurally complex ciliate cortex. It is thought to have skeletal functions concerning the spatial organization of cortical elements such as the basal bodies. Here we report the biochemical and immunological characterization of some components of the purified epiplasm of Pseudomicrothorax dubius. The epiplasm proteins consist of two quantitatively major groups of proteins, one of 76–80x103Mr, the other of 11–13x103Mr, which appear to be the principal structural elements of the epiplasm, and a series of minor components of 62–18x103Mr. Based upon lectin labeling and glycosidase treatment, some of the latter have been identified as glycoproteins. Using affinity-purified antibodies specific for individual glycoproteins or groups of glycoproteins, we were able to localize them in situ by immunoelectron microscopical methods. This in situ localization demonstrates that the glycosylated epitopes, unlike the glycoresidues of membrane proteins, are distributed throughout the entire epiplasmic layer rather than being restricted to regions adjacent to the cortical membranes. Thus, these proteins represent glycosylated, cytoskeletal elements. At least one of these glycoproteins (Mr 62x103) shows positive immunoreactivity with a monoclonal antibody (Pruss anti-IFA) recognizing most intermediate filament (IF) proteins, indicating that IF proteins might be present in protozoan cytoskeletons.

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