Justin C Crowley

Justin C Crowley
Carnegie Mellon University | CMU · Department of Biomedical Engineering

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40
Publications
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1,952
Citations
Citations since 2016
0 Research Items
449 Citations
2016201720182019202020212022020406080
2016201720182019202020212022020406080
2016201720182019202020212022020406080
2016201720182019202020212022020406080

Publications

Publications (40)
Article
Full-text available
Hemodynamic responses are commonly used to map brain activity; however, their spatial limits have remained unclear because of the lack of a well-defined and malleable spatial stimulus. To examine the properties of neural activity and hemodynamic responses, multiunit activity, local field potential, cerebral blood volume (CBV)-sensitive optical imag...
Data
Inter-map coupling strength dependent pinwheel positions. OD map, superimposed pinwheel positions (points) for different inter-map coupling strengths, . Numbers label pinwheels within the unit cell (dashed lines). Blue (green, red) points: pinwheel positions for rPWC (distorted rPWC, hPWC) solutions. A , using stationary amplitudes from Fig. (S4)(a...
Data
Map interactions with detuned wavelength and OD hexagons. . A , B , C , D , E , F . From left to right: initial condition, , , . Parameters: , mesh. Initial condition identical in all simulations. (TIF)
Data
Full-text available
Amplitude equations for the OP dynamics in case of the high order inter-map coupling energies and . (PDF)
Data
Stationary amplitudes with coupling energy , A Solid (dashed) lines: Stable (unstable) solutions. Blue: rPWC, green: distorted rPWC, red: hPWC. Black lines: stripe-like solutions. B Potential, Eq. (16), of OP stripes (black), OP rhombs (blue), and hPWC solutions (red). Arrows indicate corresponding lines in the phase diagram, Fig. (S5). (TIF)
Data
Rhombic pinwheel crystals. A OP map with superimposed OD borders (gray), 90% ipsilateral eye dominance (black), and 90% contralateral eye dominance (white), . B Selectivity , white: high selectivity, black: low selectivity. (TIF)
Data
Derivation of higher order amplitude equations and the analysis of optima for the higher order gradient-type and product-type inter-map coupling energies. (PDF)
Data
Map interactions in higher feature dimensions. A,B Map layout by interactions between three columnar systems (). All maps are mutually coupled. Superimposed on the OP map there are the borders of two real fields (black, white). A B . C,D Interactions with four columnar systems (). C . D . Superimposed on the OP map there are the borders the of thr...
Data
Full-text available
Stability matrices for the low order inter-map coupling energies. (PDF)
Data
Stationary amplitudes with coupling energy . Solid (dashed) lines: stable (unstable) solutions. A,B OD stripes, (blue), (green), (red). C,D OD hexagons, (blue), (red). A,C Transition from OP stripe solutions, B,D Transition from OP rhombic solutions. E Potential, Eq. (16), of OP stripes and OP rhombs interacting with OD stripes. F Potential, Eq. (1...
Data
A Phase diagram with coupling energy , . Vertical black lines: stability range of OD stripes, hexagons, and constant solutions. Magenta (orange) line: Stability border of orientation scotoma stripes. Green solid line: Stability border of rhombic solutions. Red solid line: Stability border of PWC solutions, red dashed line: , B Course of Eq. (27), d...
Data
Bias dependent pinwheel crystals, Eq. (27) A , B , C , D . OP map, superimposed are the OD borders (gray), 90% ipsilateral eye dominance (black), and 90% contralateral eye dominance (white), . Dashed lines mark the unit cell of the regular pattern. E,F Distribution of orientation preference. G Intersection angles between iso-orientation lines and O...
Data
Phase diagram with coupling energy , for . Vertical lines: stability range of OD hexagons, green line: transition from rPWC to distorted rPWC, red line: stability border of hPWC, blue line: stability border of distorted rPWC. Above orange line: hPWC corresponds to ground state of energy. (TIF)
Data
Map interactions with detuned wavelengths and OD stripes. C–F OD stripes interacting with OP columns where . G OD stripes interacting with OP columns where . A,B Illustration of active modes in Fourier space with , . C,D , , E–G , , C,E , D,F . G From left to right: initial condition, , , . Parameters: mesh. (TIF)
Data
Contra-center pinwheel crystals. A,B OP map, superimposed are the OD borders (gray), 90% ipsilateral eye dominance (black), and 90% contralateral eye dominance (white), . A , B . C Distribution of orientation preference. D OP map with superimposed OD map for three different values () of the OD bias. E Selectivity , white: high selectivity, black: l...
Data
Pinwheel nearest neighbor statistics and count variance with detuned wavelengths and OD stripes. (blue), (red), (green), (orange), (brown), (cyan). A–F Mean nearest neighbor pinwheel distance of arbitray A,B, equal C,D, and opposite charge E,F. G–J Standard deviation SD of pinwheel density. Shown are the fit parameters for . Dashed lines: . Paramet...
Data
Pinwheel nearest neighbor statistics and count variance with detuned wavelength and OD hexagons. 38/41 (blue), 34/41 (red), 26/41 (green), 24/41 (orange), 22/41 (violet), 20/41 (brown), 22/22 (cyan). A–F Mean nearest neighbor distance of arbitray A,B, equal C,D, and opposite charge E,F. G–J Standard deviation SD of pinwheel density. Shown are the f...
Data
Pinwheel nearest neighbor statistics and count variance in higher feature dimensions. Blue: , red: , green: , orange: . A–F Distance to the next pinwheel of arbitrary A,B, equal C,D, and opposite E,F topological charge. G–J Standard deviation SD of pinwheel density. Shown are the fit parameters for . Dashed lines: . Parameters as in Fig. 13. (TIF)
Article
Full-text available
In the primary visual cortex of primates and carnivores, functional architecture can be characterized by maps of various stimulus features such as orientation preference (OP), ocular dominance (OD), and spatial frequency. It is a long-standing question in theoretical neuroscience whether the observed maps should be interpreted as optima of a specif...
Article
Full-text available
It is an attractive hypothesis that the spatial structure of visual cortical architecture can be explained by the coordinated optimization of multiple visual cortical maps representing orientation preference (OP), ocular dominance (OD), spatial frequency, or direction preference. In part (I) of this study we defined a class of analytically tractabl...
Article
With the proliferation of both in vivo and in vitro microscopy techniques in the neurosciences, increased attention has been placed on the development of image analysis techniques. As experiments can produce large numbers of high bit depth images, automated processing methods have become necessary for handling these data sets. Thresholding, whereby...
Article
Drosophila ventral furrow formation has frequently been used as a model to study developmentally-regulated cell-shape changes. However, a technique to follow all cellular changes during this process within a single living embryo has been lacking. We describe a novel technique, called "end-on imaging", to collect time-lapse images of transversely mo...
Conference Paper
Full-text available
We propose a novel method for axonal bouton modeling and automated detection in populations of labeled neurons, as well as bouton distribution analysis for the study of neural circuit organization and plasticity. Since axonal boutons are the presynaptic specializations of neural synapses, their locations can be used to determine the organization of...
Article
Full-text available
To better understand the evolution of spatial and color vision, the number and spatial distributions of cones, rods, and optic nerve axon numbers were assessed in seven New World primates (Cebus apella, Saimiri ustius, Saguinus midas niger, Alouatta caraya, Aotus azarae, Calllithrix jacchus, and Callicebus moloch). The spatial distribution and numb...
Article
The visual system encodes and deciphers information using parallel, anatomically segregated, processing streams. To reveal patterns of gene expression in the visual thalamus correlated with physiological processing streams, we designed a custom ferret cDNA microarray. By isolating specific subregions and layers of the thalamus, we identified a set...
Article
Full-text available
Previous neurophysiological studies have reported that neurons in posterior cingulate cortex (PCC) respond after eye movements, and that these responses may vary with ambient illumination. In monkeys, PCC neurons also respond after the illumination of large visual patterns but not after the illumination of small visual targets on either reflexive s...
Article
Structural changes in hippocampal dendrites and dendritic spines are thought to be a consequence of a wide range of experience- and activity-dependent manipulations. We explored the dynamics of hippocampal dendritic spines in vivo by developing a surgical preparation of the adult mouse brain that enabled two-photon imaging of fluorescently labeled...
Article
Movement selection depends on the outcome of prior behavior. Posterior cingulate cortex (CGp) is strongly connected with both limbic and oculomotor circuitry, and CGp neurons respond following saccades, suggesting a role in signaling the motivational outcome of gaze shifts. To test this hypothesis, single CGp neurons were studied in monkeys while t...
Article
Full-text available
We examined the spatial distribution of population activity in primary visual cortex (V1) of tree shrews with optical imaging and electrophysiology. A line stimulus, thinner than the average V1 receptive field, evoked a broad strip of neural activity of nearly constant size for all stimulus locations tested within the central 10 degrees of visual s...
Article
New approaches to the study of ocular dominance development, a model system for the development of neural architecture, indicate that eye-specific columns in primary visual cortex emerge substantially before the onset of the critical period, during which neural connections can be altered by visual experience. The timing, speed and specificity of co...
Article
The development of ocular dominance columns has served as a Rosetta stone for understanding the mechanisms that guide the construction of cortical circuits. Traditionally, the emergence of ocular dominance columns was thought to be closely tied to the critical period, during which columnar architecture is highly susceptible to alterations in visual...
Article
Full-text available
The foveal specializations of five New World monkeys, the marmoset, Callithrix jacchus; the golden-handed tamarin, Saguinus midas niger; the squirrel monkey, Saimiri ustius; the capuchin monkey, Cebus apella; and the howler monkey, Alouatta caraya were compared. Although retinal area varies by over a factor of two in these monkeys, the area of the...
Article
The segregation of lateral geniculate nucleus (LGN) axons into ocular dominance columns is believed to involve a prolonged, activity-dependent sorting process. However, visualization of early postnatal ferret LGN axons by direct LGN tracer injections revealed segregated ocular dominance columns <7 days after innervation of layer 4. These early colu...
Article
Full-text available
The foveal specializations of five New World monkeys, the marmoset, Callithrix jacchus; the golden-handed tamarin, Saguinus midas niger; the squirrel monkey, Saimiri ustius; the capuchin monkey, Cebus apella; and the howler monkey, Alouatta caraya were compared. Although retinal area varies by over a factor of two in these monkeys, the area of the...
Article
The initial establishment of ocular dominance columns in visual cortex is believed to involve the segregation of overlapping geniculocortical axons into eye-specific patches based on patterns of correlated activity. However, we found that total removal of retinal influence early in visual development did not prevent segregation of geniculocortical...
Article
Purpose: To describe the scaling of retinal ganglion cell number and organization with brain size in New and Old World Primates, including humans, to contrast the relative contributions of organismal conslraints and niche to eye design. Methods: Retinal ganghon ccl! numbers, optic nerve axon numbers and retina! ganglion cell disiribution were gathe...
Article
The effects of changing retinal ganglion cell (RGC) density and availability of presynaptic sites on the development of RGC dendritic arbor in the developing chick retina were contrasted. Visual form deprivation was used to induce ocular enlargement and expanded retinal area resulting in a 20-30% decrease in RGC density. In these retinas, RGC dendr...

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