scholarly journals Functional reallocation of sensory processing resources caused by long-term neural adaptation to altered optics

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Antoine Barbot ◽  
Woon Ju Park ◽  
Cherlyn J Ng ◽  
Ru-Yuan Zhang ◽  
Krystel R Huxlin ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Sensory Processing ◽  
Visual Processing ◽  
Optical Quality ◽  
Optical Aberrations ◽  
Sensory Plasticity ◽  
Show Evidence ◽  
Processing Resources ◽  
Gains And Losses

The eye’s optics are a major determinant of visual perception. Elucidating how long-term exposure to optical defects affects visual processing is key to understanding the capacity for, and limits of, sensory plasticity. Here, we show evidence of functional reallocation of sensory processing resources following long-term exposure to poor optical quality. Using adaptive optics to bypass all optical defects, we assessed visual processing in neurotypically-developed adults with healthy eyes and with keratoconus – a corneal disease causing severe optical aberrations. Under fully-corrected optical conditions, keratoconus patients showed altered contrast sensitivity, with impaired sensitivity for fine spatial details and better-than-typical sensitivity for coarse spatial details. Both gains and losses in sensitivity were more pronounced in patients experiencing poorer optical quality in their daily life and mediated by changes in signal enhancement mechanisms. These findings show that adult neural processing adapts to better match the changes in sensory inputs caused by long-term exposure to altered optics.

scholarly journals Functional reorganization of sensory processing following long-term neural adaptation to optical defects

2020 ◽  
Author(s):  
Antoine Barbot ◽  
Woon-Ju Park ◽  
Ru-Yuan Zhang ◽  
Krystel R Huxlin ◽  
Duje Tadin ◽  
...  
Keyword(s):  
Sensory Processing ◽  
Visual Processing ◽  
Prolonged Exposure ◽  
Sensory Information ◽  
Optical Quality ◽  
Retinal Images ◽  
Optical Aberrations ◽  
Functional Reorganization

How we see is fundamentally limited by the eye’s optics, which determine retinal image quality and constrain neural processing. Elucidating how long-term exposure to optical defects alters visual processing is vital for understanding the human brain’s capacity for and limits of sensory plasticity. Using adaptive optics to bypass the eye’s optical aberrations, we assessed changes in visual processing in neurotypically-developed adults with keratoconus (KC)—a corneal disease causing severe optical aberrations during adulthood that cannot be fully corrected using conventional methods. As a result, KC patients are chronically exposed to degraded retinal images in their everyday life, making them an ideal model to understand how prolonged exposure to poor optical quality alters visual processing. Here, we show that when tested under similar fully-corrected optical conditions as neurotypical observers, KC patients exhibited altered contrast sensitivity, with impaired sensitivity for fine spatial details and better sensitivity for coarse spatial details. Both gains and losses in contrast sensitivity were more pronounced in patients with poorer habitual optical quality. Moreover, using an equivalent noise paradigm and a computational model of visual processing, we show that these alterations in visual processing are mediated by changes in signal enhancement of spatial frequency selective mechanisms. The present findings uncover fundamental properties of neural compensation mechanisms in response to long-term exposure to optical defects, which alter sensory processing and limit the benefits of improved optics. The outcome is a large-scale functional reorganization favoring the processing of sensory information less affected by the eye’s optics.Significance statementThe eye’s optics represent an intrinsic limit to human visual perception, determining the quality of retinal images. Neural adaptation optimizes the brain’s limited sensory processing capacity to the structure of the degraded retinal inputs, providing an exceptional quality of vision given these optical limitations. Here, we show that prolonged exposure to poor optical quality results in a functional reorganization of visual processing that favors sensory information less affected by the eye’s optics. The present study helps elucidate how optical factors shape the way the brain processes visual information. Notably, the resulting adaptive neural plasticity limits the immediate perceptual benefits of optical interventions, a factor that must be taken into consideration when treating the increasing human population affected by optical defects.

The Stability of the WHO Reference Thromboplastin NIBS & C 67/40

1979 ◽  
Vol 42 (04) ◽  
pp. 1135-1140 ◽  
Author(s):  
G I C Ingram
Keyword(s):  
Human Brain ◽  
Collaborative Study ◽  
Calibration Constant ◽  
Long Term Stability ◽  
Freeze Dried ◽  
Show Evidence ◽  
Human Material ◽  
Reference Preparation ◽  
The Stability

SummaryThe International Reference Preparation of human brain thromboplastin coded 67/40 has been thought to show evidence of instability. The evidence is discussed and is not thought to be strong; but it is suggested that it would be wise to replace 67/40 with a new preparation of human brain, both for this reason and because 67/40 is in a form (like Thrombotest) in which few workers seem to use human brain. A �plain� preparation would be more appropriate; and a freeze-dried sample of BCT is recommended as the successor preparation. The opportunity should be taken also to replace the corresponding ox and rabbit preparations. In the collaborative study which would be required it would then be desirable to test in parallel the three old and the three new preparations. The relative sensitivities of the old preparations could be compared with those found in earlier studies to obtain further evidence on the stability of 67/40; if stability were confirmed, the new preparations should be calibrated against it, but if not, the new human material should receive a calibration constant of 1.0 and the new ox and rabbit materials calibrated against that.The types of evidence available for monitoring the long-term stability of a thromboplastin are discussed.

scholarly journals Transformed Canine and Murine Mesenchymal Stem Cells as a Model for Sarcoma with Complex Genomics

Cancers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 1126
Author(s):  
Natasja Franceschini ◽  
Bas Verbruggen ◽  
Marianna A. Tryfonidou ◽  
Alwine B. Kruisselbrink ◽  
Hans Baelde ◽  
...  
Keyword(s):  
Copy Number ◽  
Point Mutations ◽  
Comparative Approach ◽  
Cell Of Origin ◽  
Mesenchymal Tumors ◽  
Spontaneous Transformation ◽  
Exon 2 ◽  
Species Analysis ◽  
Gains And Losses

Sarcomas are rare mesenchymal tumors with a broad histological spectrum, but they can be divided into two groups based on molecular pathology: sarcomas with simple or complex genomics. Tumors with complex genomics can have aneuploidy and copy number gains and losses, which hampers the detection of early, initiating events in tumorigenesis. Often, no benign precursors are known, which is why good models are essential. The mesenchymal stem cell (MSC) is the presumed cell of origin of sarcoma. In this study, MSCs of murine and canine origin are used as a model to identify driver events for sarcomas with complex genomic alterations as they transform spontaneously after long-term culture. All transformed murine but not canine MSCs formed sarcomas after subcutaneous injection in mice. Using whole genome sequencing, spontaneously transformed murine and canine MSCs displayed a complex karyotype with aneuploidy, point mutations, structural variants, inter-chromosomal translocations, and copy number gains and losses. Cross-species analysis revealed that point mutations in Tp53/Trp53 are common in transformed murine and canine MSCs. Murine MSCs with a cre-recombinase induced deletion of exon 2-10 of Trp53 transformed earlier compared to wild-type murine MSCs, confirming the contribution of loss of p53 to spontaneous transformation. Our comparative approach using transformed murine and canine MSCs points to a crucial role for p53 loss in the formation of sarcomas with complex genomics.

scholarly journals CD34+ human marrow cells that express low levels of Kit protein are enriched for long-term marrow-engrafting cells

Blood ◽  
1996 ◽  
Vol 87 (10) ◽  
pp. 4136-4142 ◽  
Author(s):  
I Kawashima ◽  
ED Zanjani ◽  
G Almaida-Porada ◽  
AW Flake ◽  
H Zeng ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Cells ◽  
Marrow Cell ◽  
In Utero ◽  
Fetal Sheep ◽  
Hematopoietic Stem ◽  
Show Evidence ◽  
Marrow Cells

Using in utero transplantation into fetal sheep, we examined the capability of human bone marrow CD34+ cells fractionated based on Kit protein expression to provide long-term in vivo engraftment. Twelve hundred to 5,000 CD34+ Kit-, CD34+ Kit(low), and CD34+ Kit(high) cells were injected into a total of 14 preimmune fetal sheep recipients using the amniotic bubble technique. Six fetuses were killed in utero 1.5 months after bone marrow cell transplantation. Two fetuses receiving CD34+ Kit(low) cells showed signs of engraftment according to analysis of CD45+ cells in their bone marrow cells and karyotype studies of the colonies grown in methylcellulose culture. In contrast, two fetuses receiving CD34+ Kit(high) cells and two fetuses receiving CD34+ Kit- cells failed to show evidence of significant engraftment. Two fetuses were absorbed. A total of six fetuses receiving different cell populations were allowed to proceed to term, and the newborn sheep were serially examined for the presence of chimerism. Again, only the two sheep receiving CD34+ Kit(low) cells exhibited signs of engraftment upon serial examination. Earlier in studies of murine hematopoiesis, we have shown stage-specific changes in Kit expression by the progenitors. The studies of human cells reported here are in agreement with observations in mice, and indicate that human hematopoietic stem cells are enriched in the Kit(low) population.

A New Design of Large Stroke Micro-Deformable Mirror Actuated by Electrostatic Repulsive Force

2008 ◽  
Author(s):  
Fangrong Hu ◽  
Jun Yao ◽  
Chuankai Qiu ◽  
Dajia Wang
Keyword(s):  
Electric Field ◽  
Resonant Frequency ◽  
Adaptive Optics ◽  
Bottom Electrode ◽  
Sacrificial Layer ◽  
Electrostatic Force ◽  
Repulsive Force ◽  
Deformable Mirror ◽  
Optical Aberrations ◽  
Out Of Plane

In this paper, a MEMS mirror actuated by an electrostatic repulsive force has been proposed and analyzed. The mirror consists of four U-shape springs, a fixed bottom electrode and a movable top electrode, there are many comb fingers on the edges of both electrodes. When the voltage is applied to the top and bottom electrodes, an asymmetric electric field is generated to the top movable fingers and springs, thus a net electrostatic force is produced to move the top plate out of plane. This designed micro-mirror is different from conventional MDM based on electrostatic-attractive-force, which is restricted by one-third thickness of the sacrificial layer for the pull-in phenomenon. The characteristic of this MDM has been analyzed, the result shows that the resonant frequency of the first mode is 8 kHz, and the stroke reaches 10μm at 200V, a MDM with large strokes can be realized for the application of adaptive optics in optical aberrations correction.

scholarly journals Long-term adaptation to ocular aberrations alters visual processing of spatial frequency information

2016 ◽  
Vol 16 (12) ◽  
pp. 554
Author(s):  
Antoine Barbot ◽  
Krystel Huxlin ◽  
Duje Tadin ◽  
Geunyoung Yoon
Keyword(s):  
Spatial Frequency ◽  
Visual Processing ◽  
Frequency Information ◽  
Ocular Aberrations

scholarly journals What has happened and what has not happened due to the coronavirus disease pandemic: a systemic perspective on policy change

2022 ◽  
Author(s):  
Christoph Knill ◽  
Yves Steinebach
Keyword(s):  
Policy Change ◽  
Comprehensive Analysis ◽  
Policy Agenda ◽  
Economic Crises ◽  
Policy Area ◽  
Catching Up ◽  
Policy Transformations ◽  
Gains And Losses ◽  
Academic Debate

Abstract The societal and policy transformations associated with the coronavirus disease pandemic are currently subject of intense academic debate. In this paper, we contribute to this debate by adopting a systemic perspective on policy change, shedding light on the hidden and indirect crisis effects. Based on a comprehensive analysis of policy agenda developments in Germany, we find that the pandemic led to profound shifts in political attention across policy areas. We demonstrate that these agenda gains and losses per policy area vary by the extent to which the respective areas can be presented as relevant in managing the coronavirus disease crisis and its repercussions. Moreover, relying on the analysis of past four economic crises, we also find that there is limited potential for catching up dynamics after the crisis is over. Policy areas that lost agenda share during crisis are unlikely to make up for these losses by strong attention gains once the crisis is over. Crises have hence substantial, long-term and so far, neglected effects on policymaking in modern democracies.

Layered Compound Semiconductor GaSe and GaTe Crystals for THz Applications

2006 ◽  
Vol 969 ◽  
Author(s):  
Krishna C. Mandal ◽  
Sung H. Kang ◽  
Michael K. Choi
Keyword(s):  
Wide Band ◽  
Optical Quality ◽  
Layered Compound ◽  
Bridgman Technique ◽  
Wide Band Gap ◽  
Long Term Stability ◽  
Vertical Bridgman ◽  
Thz Applications ◽  
Good Optical Quality

AbstractThe single crystal growth of layered semiconductors GaSe and GaTe by vertical Bridgman technique using zone refined selenium (Se), tellurium (Te) and high purity (HP) gallium (Ga) have been described. The grown crystals (2.5 cm diameter and ∼10 cm long) have demonstrated efficient broadband tunable THz emission and as sensitive THz detectors. The crystals have shown promising characteristics with good optical quality, high dark resistivity, wide band gap (GaSe-2.01 eV and GaTe-1.66 eV at 300 K), good anisotropic (parallel, p & perpendicular, pa) electrical properties (σ∥ vs σ⊥ and μ∥ vs σ⊥) and long term stability. Different steps involved in processing GaSe and GaTe crystals as THz sources and sensors are described.

Glutamate in the pathophysiology of schizophrenia

2020 ◽  
pp. 287-296
Author(s):  
Daniel C. Javitt
Keyword(s):  
Visual System ◽  
Visual Processing ◽  
Negative Symptoms ◽  
Glutamate Release ◽  
Critical Role ◽  
Brain Regions ◽  
Long Term Memory ◽  
Subcortical Structures ◽  
Impaired Metabolism

Glutamate theories of schizophrenia were first proposed over 30 years ago and since that time have become increasingly accepted. Theories are supported by the ability of N-methyl-D-aspartate receptor (NMDAR) antagonists such as phencyclidine (PCP) or ketamine to induce symptoms that closely resemble those of schizophrenia. Moreover, NMDAR antagonists uniquely reproduce the level of negative symptoms and cognitive deficits observed in schizophrenia, suggesting that such models may be particularly appropriate to poor outcome forms of the disorder. As opposed to dopamine, which is most prominent within frontostriatal brain regions, glutamate neurons are present throughout cortex and subcortical structures. Thus, NMDAR theories predict widespread disturbances across cortical and thalamic pathways, including sensory brain regions. In auditory cortex, NMDAR play a critical role in the generation of mismatch negativity (MMN), which may therefore serve as a translational marker of NMDAR dysfunction across species. In the visual system, NMDAR play a critical role in function of the magnocellular visual system. Deficits in both auditory and visual processing contribute to social and communication deficits, which, in turn, lead to poor functional outcome. By contrast, NMDAR dysfunction within the frontohippocampal system may contribute to well described deficits in working memory, executive processing and long-term memory formation. Deficits in NMDAR function may be driven by disturbances in presynaptic glutamate release, impaired metabolism of NMDAR modulators such as glycine or D-serine, or intrinsic abnormalities in NMDAR themselves.

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