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Primary visual cortex

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https://www.readbyqxmd.com/read/28334242/reciprocal-connections-between-cortex-and-thalamus-contribute-to-retinal-axon-targeting-to-dorsal-lateral-geniculate-nucleus
#1
Yupu Diao, Liyuan Cui, Yuqing Chen, Timothy J Burbridge, Wenqi Han, Brunhilde Wirth, Nenad Sestan, Michael C Crair, Jiayi Zhang
The dorsal Lateral Geniculate Nucleus (dLGN) is the primary image-forming target of the retina and shares a reciprocal connection with primary visual cortex (V1). Previous studies showed that corticothalamic input is essential for the development of thalamocortical projections, but less is known about the potential role of this reciprocal connection in the development of retinal projections. Here, we show a deficit of retinal innervation in the dLGN around E18.5 in Tra2β conditional knockout (cKO) "cortexless" mice, an age when apoptosis occurs along the thalamocortical tract and in some dLGN neurons...
March 10, 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/28334225/pom-thalamocortical-input-drives-layer-specific-microcircuits-in-somatosensory-cortex
#2
Nicholas J Audette, Joanna Urban-Ciecko, Megumi Matsushita, Alison L Barth
Higher-order thalamic nuclei, such as the posterior medial nucleus (POm) in the somatosensory system or the pulvinar in the visual system, densely innervate the cortex and can influence perception and plasticity. To systematically evaluate how higher-order thalamic nuclei can drive cortical circuits, we investigated cell-type selective responses to POm stimulation in mouse primary somatosensory (barrel) cortex, using genetically targeted whole-cell recordings in acute brain slices. We find that ChR2-evoked thalamic input selectively targets specific cell types in the neocortex, revealing layer-specific modules for the summation and processing of POm input...
March 10, 2017: Cerebral Cortex
https://www.readbyqxmd.com/read/28334181/uncovering-the-spatial-profile-of-contour-integration-from-fixational-saccades-evidence-for-widespread-processing-in-v1
#3
Ariel Gilad, Roy Oz, Hamutal Slovin
During contour integration, neuronal populations in the primary visual cortex (V1) enhance their responses to the contour while suppressing their responses to the noisy background. However, the spatial extent and profile of these responses are not fully understood. To investigate this question, 2 monkeys were trained on a contour detection task while we measured population responses in V1 using voltage-sensitive dyes. During stimulus presentation the animals made few fixational saccades, and we used their changing gaze position to image and analyze neuronal responses from large part of the stimulus, encoding multiple contour/background elements...
October 5, 2016: Cerebral Cortex
https://www.readbyqxmd.com/read/28333632/enhanced-just-noticeable-difference-model-for-images-with-pattern-complexity
#4
Jinjian Wu, Leida Li, Weisheng Dong, Guangming Shi, Weisi Lin, C-C Jay Kuo
The just noticeable difference (JND) in an image, which reveals the visibility limitation of the human visual system (HVS), is widely used for visual redundancy estimation in signal processing. To determine the JND threshold with the current schemes, the spatial masking effect is estimated as the contrast masking, and this cannot accurately account for the complicated interaction among visual contents. Research on cognitive science indicates that the HVS is highly adapted to extract the repeated patterns for visual content representation...
March 22, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28333587/variational-latent-gaussian-process-for-recovering-single-trial-dynamics-from-population-spike-trains
#5
Yuan Zhao, Il Memming Park
When governed by underlying low-dimensional dynamics, the interdependence of simultaneously recorded populations of neurons can be explained by a small number of shared factors, or a low-dimensional trajectory. Recovering these latent trajectories, particularly from single-trial population recordings, may help us understand the dynamics that drive neural computation. However, due to the biophysical constraints and noise in the spike trains, inferring trajectories from data is a challenging statistical problem in general...
March 23, 2017: Neural Computation
https://www.readbyqxmd.com/read/28331974/neuronal-degeneration-in-the-dorsal-lateral-geniculate-nucleus-following-lesions-of-primary-visual-cortex-comparison-of-young-adult-and-geriatric-marmoset-monkeys
#6
Nafiseh Atapour, Katrina H Worthy, Leo L Lui, Hsin-Hao Yu, Marcello G P Rosa
Neuronal loss in the lateral geniculate nucleus (LGN) is a consequence of lesions of the primary visual cortex (V1). Despite the importance of this phenomenon in understanding the residual capacities of the primate visual system following V1 damage, few quantitative studies are available, and the effect of age at the time of lesion remains unknown. We compared the volume, neuronal number, and neuronal density in the LGN, 6-21 months after unilateral V1 lesions in marmoset monkeys. Stereological sampling techniques and neuronal nuclei (NeuN) staining were used to assess the effects of similar-sized lesions in adult (2-4 years) and geriatric (10-14 years) animals...
March 22, 2017: Brain Structure & Function
https://www.readbyqxmd.com/read/28331874/the-importance-of-constructive-feedback-implications-of-top-down-regulation-in-the-development-of-neural-circuits
#7
Andrew D Thompson, Chinfei Chen
Neural circuits in sensory pathways develop through a general strategy of overproduction of synapses followed by activity-driven pruning to fine-tune connectivity for optimal function. The early visual pathway, consisting of the retina → visual thalamus → primary visual cortex, has served for decades as a powerful model system for probing the mechanisms and logic of this process. In addition to these feedforward projections, the early visual pathway also includes a substantial feedback component in the form of corticothalamic projections from the deepest layer of primary visual cortex...
2017: Neurogenesis (Austin, Tex.)
https://www.readbyqxmd.com/read/28330962/distinct-white-matter-alterations-following-severe-stroke-longitudinal-dti-study-in-neglect
#8
Roza M Umarova, Lena Beume, Marco Reisert, Christoph P Kaller, Stefan Klöppel, Irina Mader, Volkmar Glauche, Valerij G Kiselev, Marco Catani, Cornelius Weiller
OBJECTIVE: To distinguish white matter remodeling directly induced by stroke lesion from that evoked by remote network dysfunction, using spatial neglect as a model. METHODS: We examined 24 visual neglect/extinction patients and 17 control patients combining comprehensive analyses of diffusion tensor metrics and global fiber tracking with neuropsychological testing in the acute (6.3 ± 0.5 days poststroke) and chronic (134 ± 7 days poststroke) stroke phases. RESULTS: Compared to stroke controls, patients with spatial neglect/extinction displayed longitudinal white matter alterations with 2 defining signatures: (1) perilesional degenerative changes characterized by congruently reduced fractional anisotropy and increased radial diffusivity (RD), axial diffusivity, and mean diffusivity, all suggestive of direct axonal damage by lesion and therefore nonspecific for impaired attention network and (2) transneuronal changes characterized by an increased RD in contralesional frontoparietal and bilateral occipital connections, suggestive of primary periaxonal involvement; these changes were distinctly related to the degree of unrecovered neglect symptoms in chronic stroke, hence emerging as network-specific alterations...
March 22, 2017: Neurology
https://www.readbyqxmd.com/read/28320166/the-duration-of-the-cortical-silent-period-is-not-abnormal-in-restless-legs-syndrome-willis-ekbom-disease
#9
Joselisa Péres Queiroz de Paiva, Samir Câmara Magalhães, Gilmar Fernandes do Prado, Alan Luiz Eckeli, Alain Kaelin-Lang, Adriana Bastos Conforto
OBJECTIVE: To compare the duration of the cortical silent period (CSP) measured in a hand muscle in subjects with primary Restless Legs Syndrome (RLS/WED) and controls, using four different methods of analysis. METHODS: The CSP to transcranial magnetic stimulation of the dominant motor cortex was assessed in the abductor digiti minimi of 33 subjects with RLS/WED and 24 controls. CSP duration was measured by an automated and three visually-guided methods. RESULTS: There were significant differences between absolute values of CSP duration according to the method of analysis...
April 15, 2017: Journal of the Neurological Sciences
https://www.readbyqxmd.com/read/28319111/volumetric-two-photon-imaging-of-neurons-using-stereoscopy-vtwins
#10
Alexander Song, Adam S Charles, Sue Ann Koay, Jeff L Gauthier, Stephan Y Thiberge, Jonathan W Pillow, David W Tank
Two-photon laser scanning microscopy of calcium dynamics using fluorescent indicators is a widely used imaging method for large-scale recording of neural activity in vivo. Here, we introduce volumetric two-photon imaging of neurons using stereoscopy (vTwINS), a volumetric calcium imaging method that uses an elongated, V-shaped point spread function to image a 3D brain volume. Single neurons project to spatially displaced 'image pairs' in the resulting 2D image, and the separation distance between projections is proportional to depth in the volume...
March 20, 2017: Nature Methods
https://www.readbyqxmd.com/read/28318839/linking-optic-radiation-volume-to-visual-perception-in-schizophrenia-and-bipolar-disorder
#11
Eric A Reavis, Junghee Lee, Jonathan K Wynn, Katherine L Narr, Stephanie N Njau, Stephen A Engel, Michael F Green
People with schizophrenia typically show visual processing deficits on masking tasks and other performance-based measures, while people with bipolar disorder may have related deficits. The etiology of these deficits is not well understood. Most neuroscientific studies of perception in schizophrenia and bipolar disorder have focused on visual processing areas in the cerebral cortex, but perception also depends on earlier components of the visual system that few studies have examined in these disorders. Using diffusion weighted imaging (DWI), we investigated the structure of the primary sensory input pathway to the cortical visual system: the optic radiations...
March 16, 2017: Schizophrenia Research
https://www.readbyqxmd.com/read/28301866/abnormal-spontaneous-brain-activity-in-acute-low-back-pain-revealed-by-resting-state-functional-mri
#12
Shan-Shan Zhang, Wen Wu, Jian-Ming Yang, Chu-Huai Wang
OBJECTIVE: Neuroimaging studies have revealed that low-back pain (LBP) alters spatiotemporal dynamics of the blood oxygen level-dependent signal in response to persistent noxious stimulus. This study aimed to investigate changes in spontaneous neural activity of various brain regions in acute LBP using resting-state functional magnetic resonance imaging and amplitude of low-frequency fluctuation (ALFF). DESIGN: Twelve healthy subjects underwent two separate resting-state functional magnetic resonance imaging scans at health status as baseline and after intramuscular injection of hypertonic saline (0...
April 2017: American Journal of Physical Medicine & Rehabilitation
https://www.readbyqxmd.com/read/28300639/sliding-window-analysis-tracks-fluctuations-in-amygdala-functional-connectivity-associated-with-physiological-arousal-and-vigilance-during-fear-conditioning
#13
Blazej M Baczkowski, Tom Johnstone, Henrik Walter, Susanne Erk, Ilya M Veer
We evaluated whether sliding-window analysis can reveal functionally relevant brain network dynamics during a well-established fear conditioning paradigm. To this end, we tested if fMRI fluctuations in amygdala functional connectivity (FC) can be related to task-induced changes in physiological arousal and vigilance, as reflected in the skin conductance level (SCL). Thirty-two healthy individuals participated in the study. For the sliding-window analysis we used windows that were shifted by one volume at a time...
March 12, 2017: NeuroImage
https://www.readbyqxmd.com/read/28298305/population-activity-statistics-dissect-subthreshold-and-spiking-variability-in-v1
#14
Mihály Bányai, Zsombor Koman, Gergő Orbán
Response variability, as measured by fluctuating responses upon repeated performance of trials, is a major component of neural responses, and its characterization is key to interpret high dimensional population recordings. Response variability and covariability display predictable changes upon changes in stimulus and cognitive or behavioral state, providing an opportunity to test the predictive power of models of neural variability. Still, there is little agreement on which model to use as a building block for population-level analyses, and models of variability are often treated as a subject of choice...
March 15, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28293437/short-latency-gray-matter-changes-in-voxel-based-morphometry-following-high-frequent-visual-stimulation
#15
Steffen Naegel, Tim Hagenacker, Nina Theysohn, Hans-Christoph Diener, Zaza Katsarava, Mark Obermann, Dagny Holle
Magnetic resonance imaging studies using voxel-based morphometry (VBM) detected structural changes in the human brain within periods of months or weeks. The underlying molecular mechanisms of VBM findings remain unresolved. We showed that simple visual stimulation by an alternating checkerboard leads to instant, short-lasting alterations of the primary and secondary visual cortex detected by VBM. The rapidness of occurrence (i.e., within 10 minutes) rather excludes most of the proposed physiological mechanism such as neural or glial cell genesis/degeneration or synapse turnover...
2017: Neural Plasticity
https://www.readbyqxmd.com/read/28289224/patterns-of-coordinated-cortical-remodeling-during-adolescence-and-their-associations-with-functional-specialization-and-evolutionary-expansion
#16
Aristeidis Sotiras, Jon B Toledo, Raquel E Gur, Ruben C Gur, Theodore D Satterthwaite, Christos Davatzikos
During adolescence, the human cortex undergoes substantial remodeling to support a rapid expansion of behavioral repertoire. Accurately quantifying these changes is a prerequisite for understanding normal brain development, as well as the neuropsychiatric disorders that emerge in this vulnerable period. Past accounts have demonstrated substantial regional heterogeneity in patterns of brain development, but frequently have been limited by small samples and analytics that do not evaluate complex multivariate imaging patterns...
March 13, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28287987/computational-model-based-on-neural-network-of-visual-cortex-for-human-action-recognition
#17
Haihua Liu, Na Shu, Qiling Tang, Wensheng Zhang
In this paper, we propose a bioinspired model for human action recognition through modeling neural mechanisms of information processing in two visual cortical areas: the primary visual cortex (V1) and the middle temporal cortex (MT) dedicated to motion. This model, named V1-MT, is composed of V1 and MT models (layers) corresponding to their cortical areas, which are built with layered spiking neural networks (SNNs). Some neuron properties in V1 and MT, such as direction and speed selectivity, spatiotemporal inseparability, and center surround suppression, are integrated into SNNs...
March 8, 2017: IEEE Transactions on Neural Networks and Learning Systems
https://www.readbyqxmd.com/read/28273899/in-vivo-microscopic-voxel-based-morphometry-with-a-brain-template-to-characterize-strain-specific-structures-in-the-mouse-brain
#18
Keigo Hikishima, Yuji Komaki, Fumiko Seki, Yasuyuki Ohnishi, Hirotaka J Okano, Hideyuki Okano
Hundreds of inbred mouse strains are established for use in a broad spectrum of basic research fields, including genetics, neuroscience, immunology, and cancer. Inbred mice exhibit identical intra-strain genetics and divergent inter-strain phenotypes. The cognitive and behavioral divergences must be controlled by the variances of structure and function of their brains; however, the underlying morphological features of strain-to-strain difference remain obscure. Here, in vivo microscopic magnetic resonance imaging was optimized to image the mouse brains by using an isotropic resolution of 80 μm...
December 2017: Scientific Reports
https://www.readbyqxmd.com/read/28269487/cortical-responses-following-simultaneous-and-sequential-retinal-neurostimulation-with-different-return-configurations
#19
Alejandro Barriga-Rivera, John W Morley, Nigel H Lovell, Gregg J Suaning
Researchers continue to develop visual prostheses towards safer and more efficacious systems. However limitations still exist in the number of stimulating channels that can be integrated. Therefore there is a need for spatial and time multiplexing techniques to provide improved performance of the current technology. In particular, bright and high-contrast visual scenes may require simultaneous activation of several electrodes. In this research, a 24-electrode array was suprachoroidally implanted in three normally-sighted cats...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28268958/reward-value-is-encoded-in-primary-somatosensory-cortex-and-can-be-decoded-from-neural-activity-during-performance-of-a-psychophysical-task
#20
David B McNiel, John S Choi, John P Hessburg, Joseph T Francis
Encoding of reward valence has been shown in various brain regions, including deep structures such as the substantia nigra as well as cortical structures such as the orbitofrontal cortex. While the correlation between these signals and reward valence have been shown in aggregated data comprised of many trials, little work has been done investigating the feasibility of decoding reward valence on a single trial basis. Towards this goal, one non-human primate (macaca radiata) was trained to grip and hold a target level of force in order to earn zero, one, two, or three juice rewards...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
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