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Search Results: 1 - 10 of 403478 matches for " Ralph M. Siegel "
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Choices: The Science of Bela Julesz
Ralph M. Siegel
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0020172
Choices: The Science of Bela Julesz
Ralph M Siegel
PLOS Biology , 2004, DOI: 10.1371/journal.pbio.0020172
A Functional Architecture of Optic Flow in the Inferior Parietal Lobule of the Behaving Monkey
Milena Raffi, Ralph M. Siegel
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000200
Abstract: The representation of navigational optic flow across the inferior parietal lobule was assessed using optical imaging of intrinsic signals in behaving monkeys. The exposed cortex, corresponding to the dorsal-most portion of areas 7a and dorsal prelunate (DP), was imaged in two hemispheres of two rhesus monkeys. The monkeys actively attended to changes in motion stimuli while fixating. Radial expansion and contraction, and rotation clockwise and counter-clockwise optic flow stimuli were presented concentric to the fixation point at two angles of gaze to assess the interrelationship between the eye position and optic flow signal. The cortical response depended upon the type of flow and was modulated by eye position. The optic flow selectivity was embedded in a patchy architecture within the gain field architecture. All four optic flow stimuli tested were represented in areas 7a and DP. The location of the patches varied across days. However the spatial periodicity of the patches remained constant across days at ~950 and 1100 μm for the two animals examined. These optical recordings agree with previous electrophysiological studies of area 7a, and provide new evidence for flow selectivity in DP and a fine scale description of its cortical topography. That the functional architectures for optic flow can change over time was unexpected. These and earlier results also from inferior parietal lobule support the inclusion of both static and dynamic functional architectures that define association cortical areas and ultimately support complex cognitive function.
Francis Crick's Legacy for Neuroscience: Between the α and the Ω
Ralph M. Siegel,Edward M. Callaway
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0020419
Francis Crick's Legacy for Neuroscience: Between the α and the Ω
Ralph M Siegel ,Edward M Callaway
PLOS Biology , 2004, DOI: 10.1371/journal.pbio.0020419
Two-Photon Imaging of Calcium in Virally Transfected Striate Cortical Neurons of Behaving Monkey
Barbara Heider,Jason L. Nathanson,Ehud Y. Isacoff,Edward M. Callaway,Ralph M. Siegel
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013829
Abstract: Two-photon scanning microscopy has advanced our understanding of neural signaling in non-mammalian species and mammals. Various developments are needed to perform two-photon scanning microscopy over prolonged periods in non-human primates performing a behavioral task. In striate cortex in two macaque monkeys, cortical neurons were transfected with a genetically encoded fluorescent calcium sensor, memTNXL, using AAV1 as a viral vector. By constructing an extremely rigid and stable apparatus holding both the two-photon scanning microscope and the monkey's head, single neurons were imaged at high magnification for prolonged periods with minimal motion artifacts for up to ten months. Structural images of single neurons were obtained at high magnification. Changes in calcium during visual stimulation were measured as the monkeys performed a fixation task. Overall, functional responses and orientation tuning curves were obtained in 18.8% of the 234 labeled and imaged neurons. This demonstrated that the two-photon scanning microscopy can be successfully obtained in behaving primates.
Attachment and Academic Classroom Behavior: Self-Efficacy and Procrastination as Moderators on the Influence of Attachment on Academic Success  [PDF]
Robert M. Kurland, Harold I. Siegel
Psychology (PSYCH) , 2016, DOI: 10.4236/psych.2016.78107
Abstract: Attachment, self-efficacy, and procrastination were measured in 161 college students enrolled in an Introductory Psychology class. Class grades and overall academic records were also obtained. Students who had higher levels of attachment anxiety had lower final grades in the class, higher levels of procrastination, and lower self-efficacy. Students with higher levels of attachment avoidance had lower grades within the class and a lower overall Grade Point Average (GPA). Regression analysis showed that self-efficacy moderated the relationship between attachment and class grade as well as overall GPA. Procrastination also moderated the relationship between both attachment anxiety and GPA and attachment avoidance and GPA.
Functional Implications of Sleep Development
Jerome M. Siegel
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0030178
Functional Implications of Sleep Development
Jerome M Siegel
PLOS Biology , 2005, DOI: 10.1371/journal.pbio.0030178
Excitation of non-radial stellar oscillations by gravitational waves: a first model
D. M. Siegel,M. Roth
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17240.x
Abstract: The excitation of solar and solar-like g modes in non-relativistic stars by arbitrary external gravitational wave fields is studied starting from the full field equations of general relativity. We develop a formalism that yields the mean-square amplitudes and surface velocities of global normal modes excited in such a way. The isotropic elastic sphere model of a star is adopted to demonstrate this formalism and for calculative simplicity. It is shown that gravitational waves solely couple to quadrupolar spheroidal eigenmodes and that normal modes are only sensitive to the spherical component of the gravitational waves having the same azimuthal order. The mean-square amplitudes in case of stationary external gravitational waves are given by a simple expression, a product of a factor depending on the resonant properties of the star and the power spectral density of the gravitational waves' spherical accelerations. Both mean-square amplitudes and surface velocities show a characteristic R^8-dependence (effective R^2-dependence) on the radius of the star. This finding increases the relevance of this excitation mechanism in case of stars larger than the Sun.
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