The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
David Ress - One of the best experts on this subject based on the ideXlab platform.
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Polar Angle representation of saccadic eye movements in human superior colliculus
NeuroImage, 2017Co-Authors: Ricky R Savjani, Sucharit Katyal, Elizabeth J Halfen, David RessAbstract:Abstract The superior colliculus (SC) is a layered midbrain structure involved in directing both head and eye movements and coordinating visual attention. Although a retinotopic organization for the mediation of saccadic eye-movements has been shown in monkey SC, in human SC the topography of saccades has not been confirmed. Here, a novel experimental paradigm was performed by five participants (one female) while high-resolution (1.2-mm) functional magnetic resonance imaging was used to measure activity evoked by saccadic eye movements within human SC. Results provide three critical observations about the topography of the SC: (1) saccades along the superior-inferior visual axis are mapped across the medial-lateral anatomy of the SC; (2) the saccadic eye-movement representation is in register with the retinotopic organization of visual stimulation; and (3) activity evoked by saccades occurs deeper within SC than that evoked by visual stimulation. These approaches lay the foundation for studying the organization of human subcortical – and enhanced cortical mapping – of eye-movement mechanisms.
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Polar Angle representation of saccadic eye movements in human superior colliculus
bioRxiv, 2017Co-Authors: Ricky R Savjani, Elizabeth J Halfen, David RessAbstract:The superior colliculus (SC) is a layered midbrain structure involved in directing eye movements and coordinating visual attention. Electrical stimulation and neuronal recordings in the intermediate layers of monkey SC have shown a retinotopic organization for the mediation of saccadic eye-movements. However, in human SC the topography of saccades is unknown. Here, a novel experimental paradigm and high-resolution (1.2-mm) functional magnetic resonance imaging methods were used to measure activity evoked by saccadic eye movements within SC. Results provide three critical observations about the topography of the human SC: (1) saccades along the superior-inferior visual axis are mapped across the medial-lateral anatomy of the SC; (2) the saccadic eye-movement representation is in register with the retinotopic organization of visual stimulation; and (3) activity evoked by saccades occurs deeper within SC than that evoked by visual stimulation. These approaches lay the foundation for studying the organization of human subcortical eye-movement mechanisms.
Ricky R Savjani - One of the best experts on this subject based on the ideXlab platform.
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Polar Angle representation of saccadic eye movements in human superior colliculus
NeuroImage, 2017Co-Authors: Ricky R Savjani, Sucharit Katyal, Elizabeth J Halfen, David RessAbstract:Abstract The superior colliculus (SC) is a layered midbrain structure involved in directing both head and eye movements and coordinating visual attention. Although a retinotopic organization for the mediation of saccadic eye-movements has been shown in monkey SC, in human SC the topography of saccades has not been confirmed. Here, a novel experimental paradigm was performed by five participants (one female) while high-resolution (1.2-mm) functional magnetic resonance imaging was used to measure activity evoked by saccadic eye movements within human SC. Results provide three critical observations about the topography of the SC: (1) saccades along the superior-inferior visual axis are mapped across the medial-lateral anatomy of the SC; (2) the saccadic eye-movement representation is in register with the retinotopic organization of visual stimulation; and (3) activity evoked by saccades occurs deeper within SC than that evoked by visual stimulation. These approaches lay the foundation for studying the organization of human subcortical – and enhanced cortical mapping – of eye-movement mechanisms.
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Polar Angle representation of saccadic eye movements in human superior colliculus
bioRxiv, 2017Co-Authors: Ricky R Savjani, Elizabeth J Halfen, David RessAbstract:The superior colliculus (SC) is a layered midbrain structure involved in directing eye movements and coordinating visual attention. Electrical stimulation and neuronal recordings in the intermediate layers of monkey SC have shown a retinotopic organization for the mediation of saccadic eye-movements. However, in human SC the topography of saccades is unknown. Here, a novel experimental paradigm and high-resolution (1.2-mm) functional magnetic resonance imaging methods were used to measure activity evoked by saccadic eye movements within SC. Results provide three critical observations about the topography of the human SC: (1) saccades along the superior-inferior visual axis are mapped across the medial-lateral anatomy of the SC; (2) the saccadic eye-movement representation is in register with the retinotopic organization of visual stimulation; and (3) activity evoked by saccades occurs deeper within SC than that evoked by visual stimulation. These approaches lay the foundation for studying the organization of human subcortical eye-movement mechanisms.
Ben M Harvey - One of the best experts on this subject based on the ideXlab platform.
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radial asymmetries in population receptive field size and cortical magnification factor in early visual cortex
NeuroImage, 2018Co-Authors: Maria De Fatima Silva, Serge O Dumoulin, Jan W Brascamp, Sonia Ferreira, Miguel Castelobranco, Ben M HarveyAbstract:Abstract Human visual cortex does not represent the whole visual field with the same detail. Changes in receptive field size, population receptive field (pRF) size and cortical magnification factor (CMF) with eccentricity are well established, and associated with changes in visual acuity with eccentricity. Visual acuity also changes across Polar Angle. However, it remains unclear how RF size, pRF size and CMF change across Polar Angle. Here, we examine differences in pRF size and CMF across Polar Angle in V1, V2 and V3 using pRF modeling of human fMRI data. In these visual field maps, we find smaller pRFs and larger CMFs in horizontal (left and right) than vertical (upper and lower) visual field quadrants. Differences increase with eccentricity, approximately in proportion to average pRF size and CMF. Similarly, we find larger CMFs in the lower than upper quadrant, and again differences increase with eccentricity. However, pRF size differences between lower and upper quadrants change direction with eccentricity. Finally, we find slightly smaller pRFs in the left than right quadrants of V2 and V3, though this difference is very small, and we find no differences in V1 and no differences in CMF. Moreover, differences in pRF size and CMF vary gradually with Polar Angle and are not limited to the meridians or visual field map discontinuities. PRF size and CMF differences do not consistently follow patterns of cortical curvature, despite the link between cortical curvature and Polar Angle in V1. Thus, the early human visual cortex has a radially asymmetric representation of the visual field. These asymmetries may underlie consistent reports of asymmetries in perceptual abilities.
Hai Lu - One of the best experts on this subject based on the ideXlab platform.
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azimuthal illumination enabled ultra high Polar Angle sensitivity by a bloch surface wave resonance refractive index sensor
Journal of Physics D, 2020Co-Authors: Xiubao Kang, Hai LuAbstract:The scheme of a Polar Angle space refractive index (RI) sensor based on grating-coupled Bloch surface wave (BSW) resonance excited by azimuthal illuminations is studied. It is shown that, for any Polar Angle, one can always find a case of BSW resonance with the tangential wave vector of the BSW mode perpendicular to that of the incident electromagnetic wave. When the sensor is designed to work around this BSW resonance, ultra-high Polar Angle sensitivity can be expected. The numerical simulated Polar Angle sensitivity reaches as large as 1786 degrees per RI unit (Deg/RIU), which is almost one order higher than that found in the literature.
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Guided Bloch surface wave resonance by near normal and near in-plane illuminations: the hyper azimuthal sensitivity.
Optics Express, 2018Co-Authors: Xiubao Kang, Hai Lu, Zhi-guo WangAbstract:Refractive index sensors based on the interrogation of guided Bloch surface wave resonance (GBR) in the azimuthal Angle domain are studied both theoretically and numerically. The azimuthal sensitivity of the sensors is shown to be inversely proportional to the sines of both the azimuthal Angle and the Polar Angle of the detecting electromagnetic signals. Extremely large azimuthal sensitivity is then achieved when the GBR sensor is designed to work near a small azimuthal Angle and the Polar Angle is also fixed to a small one (For the azimuthal Angle domain near φ = 5° and a fixed Polar Angle of θ = 5°, the azimuthal sensitivity gets larger than 5000 degrees per refractive index unit (Deg/RIU)).
Nabil N. Abd Allah - One of the best experts on this subject based on the ideXlab platform.
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Dependence of black fragment azimuthal and projected angular distributions on Polar Angle in silicon-emulsion collisions at 4.5A GeV/c
Physical Review C, 2004Co-Authors: Nabil N. Abd Allah, Brajesh K. SinghAbstract:The experimental results of dependence of black fragment azimuth sfd and projected Angle scd distributions on Polar Angle u in silicon-emulsion collisions at 4.5 A GeV/c (the Dubna momentum) are reported. There are two regions of enhancement around f = ± 90° for different u ranges. These enhancements are due to directed sv1d and elliptic sv2d flows. The v1 and v2 dependence of values on u shows that the directed flow is weak and the elliptic flow is strong in these collisions. A multisource ideal gas model is used to describe the experimental results of dependence. The Monte Carlo calculated results are approximately in agreement with the experimental data.
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dependence of black fragment azimuthal and projected angular distributions on Polar Angle in silicon emulsion collisions at 4 5a gev c
Physical Review C, 2004Co-Authors: Nabil N. Abd Allah, Brajesh K. SinghAbstract:The experimental results of dependence of black fragment azimuth sfd and projected Angle scd distributions on Polar Angle u in silicon-emulsion collisions at 4.5 A GeV/c (the Dubna momentum) are reported. There are two regions of enhancement around f = ± 90° for different u ranges. These enhancements are due to directed sv1d and elliptic sv2d flows. The v1 and v2 dependence of values on u shows that the directed flow is weak and the elliptic flow is strong in these collisions. A multisource ideal gas model is used to describe the experimental results of dependence. The Monte Carlo calculated results are approximately in agreement with the experimental data.