scholarly journals TMS reveals inhibitory extrastriate cortico-cortical feedback modulation of V1 activity in humans

2019 ◽  
Vol 224 (9) ◽  
pp. 3399-3408 ◽  
Author(s):  
M. Maniglia ◽  
Y. Trotter ◽  
F. Aedo-Jury
Keyword(s):  
Direct Evidence ◽  
Building Blocks ◽  
Contextual Modulation ◽  
Lateral Masking ◽  
Retinotopic Mapping ◽  
Horizontal Connections ◽  
Visual Areas ◽  
Contrast Thresholds ◽  
Collinear Facilitation ◽  
First Time

Abstract The interaction between the primary visual cortex (V1) and extrastriate visual areas provides the first building blocks in our perception of the world. V2, in particular, seems to play a crucial role in shaping contextual modulation information through feedback projections to V1. However, whether this feedback is inhibitory or excitatory is still unclear. In order to test the nature of V2 feedback to V1, we used neuronavigation-guided offline inhibitory transcranial magnetic stimulation (TMS) on V2 before testing participants on collinear facilitation, a contrast detection task with lateral masking. This contextual modulation task is thought to rely on horizontal connections in V1 and possibly extrastriate feedback. Results showed that when inhibitory TMS was delivered over V2, contrast thresholds decreased for targets presented in the contralateral hemifield, consistent with the retinotopic mapping of this area, while having no effect for targets presented in the ipsilateral hemifield or after control (CZ) stimulation. These results suggest that feedback from V2 to V1 during contextual modulation is mostly inhibitory, corroborating recent observations in monkey electrophysiology and extending this mechanism to human visual system. Moreover, we provide for the first time direct evidence of the involvement of extrastriate visual areas in collinear facilitation.

Differential Contribution of Early Visual Areas to the Perceptual Process of Contour Processing

2004 ◽  
Vol 91 (4) ◽  
pp. 1716-1721 ◽  
Author(s):  
Mark M. Schira ◽  
Manfred Fahle ◽  
Tobias H. Donner ◽  
Antje Kraft ◽  
Stephan A. Brandt
Keyword(s):  
Discrimination Task ◽  
Visual Awareness ◽  
Blood Oxygenation ◽  
Signal Modulation ◽  
Contextual Modulation ◽  
Central Figure ◽  
Retinotopic Mapping ◽  
Visual Areas ◽  
Oxygenation Level

We investigated contour processing and figure–ground detection within human retinotopic areas using event-related functional magnetic resonance imaging (fMRI) in 6 healthy and naïve subjects. A figure (6° side length) was created by a 2nd-order texture contour. An independent and demanding foveal letter-discrimination task prevented subjects from noticing this more peripheral contour stimulus. The contour subdivided our stimulus into a figure and a ground. Using localizers and retinotopic mapping stimuli we were able to subdivide each early visual area into 3 eccentricity regions corresponding to 1) the central figure, 2) the area along the contour, and 3) the background. In these subregions we investigated the hemodynamic responses to our stimuli and compared responses with or without the contour defining the figure. No contour-related blood oxygenation level–dependent modulation in early visual areas V1, V3, VP, and MT+ was found. Significant signal modulation in the contour subregions of V2v, V2d, V3a, and LO occurred. This activation pattern was different from comparable studies, which might be attributable to the letter-discrimination task reducing confounding attentional modulation. In V3a, but not in any other retinotopic area, signal modulation corresponding to the central figure could be detected. Such contextual modulation will be discussed in light of the recurrent processing hypothesis and the role of visual awareness.

Probing the Substrate Promiscuity of Isopentenyl Phosphate Kinase as a Platform for Hemiterpene Analogue Production

2019 ◽  
Author(s):  
Sean Lund ◽  
Taylor Courtney ◽  
Gavin Williams
Keyword(s):  
Synthetic Biology ◽  
Building Blocks ◽  
Isoprenoid Biosynthesis ◽  
Thermoplasma Acidophilum ◽  
Substrate Promiscuity ◽  
Enzymatic Pathways ◽  
First Time ◽  
Rate Limiting ◽  
Alcohol Dependent ◽  
Isopentenyl Phosphate

Isoprenoids are a large class of natural products with wide-ranging applications. Synthetic biology approaches to the manufacture of isoprenoids and their new-to-nature derivatives are limited due to the provision in Nature of just two hemiterpene building blocks for isoprenoid biosynthesis. To address this limitation, artificial chemo-enzymatic pathways such as the alcohol-dependent hemiterpene pathway (ADH) serve to leverage consecutive kinases to convert exogenous alcohols to pyrophosphates that could be coupled to downstream isoprenoid biosynthesis. To be successful, each kinase in this pathway should be permissive of a broad range of substrates. For the first time, we have probed the promiscuity of the second enzyme in the ADH pathway, isopentenyl phosphate kinase from Thermoplasma acidophilum, towards a broad range of acceptor monophosphates. Subsequently, we evaluate the suitability of this enzyme to provide non-natural pyrophosphates and provide a critical first step in characterizing the rate limiting steps in the artificial ADH pathway.<br>

scholarly journals A Sustainable Improvement of ω-Bromoalkylphosphonates Synthesis to Access Novel KuQuinones

Organics ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 107-117
Author(s):  
Mattia Forchetta ◽  
Valeria Conte ◽  
Giulia Fiorani ◽  
Pierluca Galloni ◽  
Federica Sabuzi
Keyword(s):  
Metal Oxides ◽  
Phosphonic Acid ◽  
Organic Molecules ◽  
Building Blocks ◽  
Reaction Conditions ◽  
Phosphonic Acids ◽  
Sustainable Improvement ◽  
Phosphonate Esters ◽  
First Time ◽  
Complex Organic

Owing to the attractiveness of organic phosphonic acids and esters in the pharmacological field and in the functionalization of conductive metal-oxides, the research of effective synthetic protocols is pivotal. Among the others, ω-bromoalkylphosphonates are gaining particular attention because they are useful building blocks for the tailored functionalization of complex organic molecules. Hence, in this work, the optimization of Michaelis–Arbuzov reaction conditions for ω-bromoalkylphosphonates has been performed, to improve process sustainability while maintaining good yields. Synthesized ω-bromoalkylphosphonates have been successfully adopted for the synthesis of new KuQuinone phosphonate esters and, by hydrolysis, phosphonic acid KuQuinone derivatives have been obtained for the first time. Considering the high affinity with metal-oxides, KuQuinones bearing phosphonic acid terminal groups are promising candidates for biomedical and photo(electro)chemical applications.

scholarly journals Bacterial cellulose spheroids as building blocks for 3D and patterned living materials and for regeneration

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Joaquin Caro-Astorga ◽  
Kenneth T. Walker ◽  
Natalia Herrera ◽  
Koon-Yang Lee ◽  
Tom Ellis
Keyword(s):  
Bacterial Cellulose ◽  
Building Blocks ◽  
Genetically Engineered ◽  
High Yield ◽  
Synthetic Materials ◽  
Chemical Inputs ◽  
First Time ◽  
3D Shapes ◽  
Promising Avenue ◽  
Living Materials

AbstractEngineered living materials (ELMs) based on bacterial cellulose (BC) offer a promising avenue for cheap-to-produce materials that can be programmed with genetically encoded functionalities. Here we explore how ELMs can be fabricated in a modular fashion from millimetre-scale biofilm spheroids grown from shaking cultures of Komagataeibacter rhaeticus. Here we define a reproducible protocol to produce BC spheroids with the high yield bacterial cellulose producer K. rhaeticus and demonstrate for the first time their potential for their use as building blocks to grow ELMs in 3D shapes. Using genetically engineered K. rhaeticus, we produce functionalized BC spheroids and use these to make and grow patterned BC-based ELMs that signal within a material and can sense and report on chemical inputs. We also investigate the use of BC spheroids as a method to regenerate damaged BC materials and as a way to fuse together smaller material sections of cellulose and synthetic materials into a larger piece. This work improves our understanding of BC spheroid formation and showcases their great potential for fabricating, patterning and repairing ELMs based on the promising biomaterial of bacterial cellulose.

Design, synthesis and evaluation of structurally diverse ortho-acylphenol-diindolylmethane hybrids as anticancer agents

2022 ◽  
Author(s):  
Zhi-Gang Yin ◽  
Xiong-Wei Liu ◽  
Hui-Juan Wang ◽  
Min Zhang ◽  
Xiong-Li Liu ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Anticancer Agents ◽  
Nucleophilic Addition ◽  
Ring Opening ◽  
Building Blocks ◽  
Efficient Synthesis ◽  
Design Synthesis ◽  
Pyrone Ring ◽  
Ring Opening Reaction ◽  
First Time

A highly efficient synthesis of structurally diverse ortho-acylphenol–diindolylmethane hybrids 3 using carboxylic acid-activated chromones as versatile synthetic building blocks is reported here for the first time, through 1,4-nucleophilic addition and followed by a decarboxylation and pyrone ring opening reaction process.

scholarly journals Straightforward Preparation of Supramolecular Janus Nanorods by Hydrogen Bonding of End-Functionalized Polymers

2020 ◽  
Author(s):  
Shuaiyuan Han ◽  
Sandrine Pensec ◽  
Cédric Lorthioir ◽  
Jacques Jestin ◽  
Jean-Michel Guigner ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Functional Materials ◽  
Phase Segregation ◽  
Building Blocks ◽  
Functionalized Polymers ◽  
Nanometer Range ◽  
One Dimensional ◽  
Oil In Water ◽  
First Time

Janus cylinders are one-dimensional colloids that have two faces with different compositions and functionalities and are useful as building blocks for advanced functional materials. Such anisotropic objects are difficult to prepare with nanometric dimensions. Here we describe a robust and versatile strategy to form micrometer long Janus nanorods with diameters in the 10-nanometer range, by self-assembly in water of end-functionalized polymers. For the first time, the Janus topology is not a result of the phase segregation of incompatible polymer arms, but is driven by the interactions between unsymmetrical and complementary hydrogen bonded stickers. It is therefore independent of the actual polymers used and works even for compatible polymers. To illustrate their applicative potential, we show that these Janus nanorods can efficiently stabilize oil-in-water emulsions.

scholarly journals Multi-static spatial and angular studies of polar mesospheric summer echoes combining MAARSY and KAIRA

2018 ◽  
Author(s):  
Jorge L. Chau ◽  
Derek McKay ◽  
Juha P. Vierinen ◽  
Cesar La Hoz ◽  
Thomas Ulich ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Middle Atmosphere ◽  
Lower Sensitivity ◽  
Wind Fields ◽  
Receiver Array ◽  
Schmidt Numbers ◽  
Summer Echoes ◽  
Imaging Receiver ◽  
Highly Correlated ◽  
First Time

Abstract. Polar mesospheric summer echoes (PMSEs) have been long associated with Noctilucent clouds (NLCs). For large ice particles sizes and relatively high ice densities, PMSE and NLCs have been shown to be highly correlated at 3-m Bragg wavelengths and are known to be good tracers of the atmospheric wind dynamics. Combining the Middle Atmosphere ALOMAR Radar System (MAARSY) and the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA), i.e., monostatic and bistatic observations, we show for the first time direct evidence of limited-volume PMSE structures drifting more than 90 km almost unchanged. These structures are shown to have widths of 5–15 km and are separated by 20–60 kms, consistent with structures due to atmospheric waves previously observed in NLCs from the ground and from space. Given the lower sensitivity of KAIRA, the observed features are attributed to echoes from regions with high Schmidt numbers that provide a large radar cross-section. The bistatic geometry allows us to determine an upper value for the angular sensitivity of PMSE echoes at meter scales. We find no evidence for strong aspect sensitivity for PMSE echoes, which is consistent with recent observations using radar imaging approaches. Our results indicate that multi-static all-sky interferometric radar observations of PMSE could be a powerful tool for studying mesospheric wind-fields within large geographic areas.

scholarly journals Direct evidence of charge separation in a metal–organic framework: efficient and selective photocatalytic oxidative coupling of amines via charge and energy transfer

2018 ◽  
Vol 9 (12) ◽  
pp. 3152-3158 ◽  
Author(s):  
Caiyun Xu ◽  
Hang Liu ◽  
Dandan Li ◽  
Ji-Hu Su ◽  
Hai-Long Jiang
Keyword(s):  
Energy Transfer ◽  
Charge Separation ◽  
Oxidative Coupling ◽  
Direct Evidence ◽  
Metal Organic Framework ◽  
Metal Organic ◽  
First Time ◽  
Organic Framework

For the first time, the photoexcited charge separation in a metal–organic framework has been evidenced with clear ESR signals, based on efficient and selective photocatalytic oxidative coupling of amines.

scholarly journals A fast and versatile cross-linking strategy via o-phthalaldehyde condensation for mechanically strengthened and functional hydrogels

2020 ◽  
Author(s):  
Zhen Zhang ◽  
Chaoliang He ◽  
Yan Rong ◽  
Hui Ren ◽  
Tianran Wang ◽  
...  
Keyword(s):  
Condensation Reaction ◽  
Building Blocks ◽  
Order Rate Constant ◽  
Cross Linking ◽  
Click Reactions ◽  
Oxime Formation ◽  
Cross Links ◽  
Poly Ethylene ◽  
Molecule Model ◽  
First Time

Abstract Fast and catalyst-free cross-linking strategy is of great significance for construction of covalently cross-linked hydrogels. Here, we report the condensation reaction between o-phthalaldehyde (OPA) and N-nucleophiles (primary amine, hydrazide and aminooxy) for hydrogel formation for the first time. When four-arm poly(ethylene glycol) (4aPEG) capped with OPA was mixed with various N-nucleophile-terminated 4aPEG as building blocks, hydrogels were formed with superfast gelation rate, higher mechanical strength and markedly lower critical gelation concentrations, compared to benzaldehyde-based counterparts. Small molecule model reactions indicate the key to these cross-links is the fast formation of heterocycle phthalimidine product or isoindole (bis)hemiaminal intermediates, depending on the N-nucleophiles. The second-order rate constant for the formation of phthalimidine linkage (4.3 M−1 s−1) is over 3000 times and 200 times higher than those for acylhydrazone and oxime formation from benzaldehyde, respectively, and comparable to many cycloaddition click reactions. Based on the versatile OPA chemistry, various hydrogels can be readily prepared from naturally derived polysaccharides, proteins or synthetic polymers without complicated chemical modification. Moreover, biofunctionality is facilely imparted to the hydrogels by introducing amine-bearing peptides via the reaction between OPA and amino group.

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