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Primary visual cortex

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https://www.readbyqxmd.com/read/29046110/image-sharpness-and-contrast-tuning-in-the-early-visual-pathway
#1
Eduardo Sánchez, Rubén Ferreiroa, Adrián Arias, Luis M Martínez
The center-surround organization of the receptive fields (RFs) of retinal ganglion cells highlights the presence of local contrast in visual stimuli. As RF of thalamic relay cells follow the same basic functional organization, it is often assumed that they contribute very little to alter the retinal output. However, in many species, thalamic relay cells largely outnumber their retinal inputs, which diverge to contact simultaneously several units at thalamic level. This gain in cell population as well as retinothalamic convergence opens the door to question how information about contrast is transformed at the thalamic stage...
September 7, 2017: International Journal of Neural Systems
https://www.readbyqxmd.com/read/29042433/serotonin-decreases-the-gain-of-visual-responses-in-awake-macaque-v1
#2
Lenka Seillier, Corinna Lorenz, Katsuhisa Kawaguchi, Torben Ott, Andreas Nieder, Paria Pourriahi, Hendrikje Nienborg
Serotonin (5HT) is an important neuromodulator in the brain implicated in affective and cognitive functions but its role even for basic cortical processes is controversial. For example, in the mammalian primary visual cortex heterogenous serotonergic modulation has been observed in anesthetized animals. Here, we combined extracellular single unit recordings with iontophoresis in awake animals. We examined the role of serotonin on well-defined tuning properties (orientation, spatial frequency, contrast and size) in the primary visual cortex (V1) of two male macaque monkeys...
October 17, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/29031852/inhibition-of-cdk5-rejuvenates-inhibitory-circuits-and-restores-experience-dependent-plasticity-in-adult-visual-cortex
#3
Yue Li, Laijian Wang, Xinxin Zhang, Mengyao Huang, Sitong Li, Xinxing Wang, Lin Chen, Bin Jiang, Yupeng Yang
Cyclin-dependent kinase 5 (Cdk5) acts as an essential modulator for neural development and neurological disorders. Here we show that Cdk5 plays a pivotal role in modulating GABAergic signaling and the maturation of visual system. In adult mouse primary visual cortex, Cdk5 formed complex with the GABA synthetic enzyme glutamate decarboxylase GAD67, but not with GAD65. In addition to enhancement in the surface level of NR2B-containing NMDA receptors, inhibition of Cdk5 reduced the protein levels of GADs and Otx2, while leaving intact the expression of vesicular GABA transporter and subunits of GABAA or AMPA receptors...
October 12, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/29031837/impaired-contrast-sensitivity-at-low-spatial-frequency-in-cannabis-users-with-early-onset
#4
Laurence Lalanne, Eglantine Ferrand-Devouge, Sebastien Kirchherr, Lucie Rauch, Estelle Koning, Claude Speeg, Vincent Laprevote, Anne Giersch
The regular use of cannabis generates pronounced cognitive disorders, especially in users who begin before the age of 15-16. However, less is known about the impact of regular cannabis on visual function, especially in the case of early onset. Cannabinoid receptors (CB1) are expressed in areas of the visual system, like the thalamus and primary cortex, which might originate sensory disorders. Hence, we measured contrast sensitivity (CS) in three groups, i.e. cannabis users with late onset of cannabis use (after 16 years old), cannabis users with early onset"...
October 11, 2017: European Neuropsychopharmacology: the Journal of the European College of Neuropsychopharmacology
https://www.readbyqxmd.com/read/29031533/structural-changes-in-brain-morphology-induced-by-brief-periods-of-repetitive-sensory-stimulation
#5
T Schmidt-Wilcke, N Wulms, S Heba, B Pleger, N A Puts, B Glaubitz, T Kalisch, M Tegenthoff, H R Dinse
There is a growing interest in identifying the neural mechanisms by which the human brain allows for improving performance. Tactile perceptual measurements, e.g. two-point discrimination (2ptD), can be used to investigate neural mechanisms of perception as well as perceptual improvement. Improvement can be induced in a practice-independent manner, e.g. in the tactile domain through repetitive somatosensory stimulation (rSS). With respect to tactile perception, the role of cortical excitability and activation within the somatosensory cortex has been investigated extensively...
October 11, 2017: NeuroImage
https://www.readbyqxmd.com/read/29025168/-a-model-explaining-infantile-esotropia-dissociated-strabismus-as-a-result-of-sensory-interhemispheric-dissociation-and-crossed-dominance-in-the-brainstem
#6
Marcel Paulus Ten Tusscher
Over 150 million years, modern reptiles, birds and mammals evolved. Predatory birds and mammals have eyes on the front of their heads. In these animals, binocular correspondence, voluntary eye movements, eye-hand coordination, partial decussation at the optic chiasm and cortical interhemispheric pathways could develop at the cost of a smaller visual field. The subsequent enlargement of the cerebral neocortex and the hemispheric pathways are of central importance in binocular vision, sensory fusion and infantile strabismus...
October 2017: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/29020625/overproduction-of-neurons-is-correlated-with-enhanced-cortical-ensembles-and-increased-perceptual-discrimination
#7
Wei-Qun Fang, Rafael Yuste
Brains vary greatly in neuronal number and density, even across individuals within the same species, yet it remains unclear whether such variation leads to differences in brain function or behavior. By imaging cortical activity of a mouse model in which neuronal production is moderately enhanced in utero, we find that animals with more cortical neurons also develop enhanced functional correlations and more distinct neuronal ensembles in primary visual cortex. These mice also have sharper orientation discrimination in their visual behavior...
October 10, 2017: Cell Reports
https://www.readbyqxmd.com/read/28994763/effects-of-transcranial-alternating-current-stimulation-on-the-primary-motor-cortex-by-online-combined-approach-with-transcranial-magnetic-stimulation
#8
Anna Shpektor, Maria Nazarova, Matteo Feurra
Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific frequency and in turn modulate ongoing cortical oscillatory activity. This neurotool allows the establishment of a causal link between endogenous oscillatory activity and behavior. Most of the tACS studies have shown online effects of tACS. However, little is known about the underlying action mechanisms of this technique because of the AC-induced artifacts on Electroencephalography (EEG) signals...
September 23, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28991743/curvature-integration-in-a-5d-kernel-for-extracting-vessel-connections-in-retinal-images
#9
Samaneh Abbasi-Sureshjani, Marta Favali, Giovanna Citti, Alessandro Sarti, Bart M Ter Haar Romeny
Tree-like structures such as retinal images are widely studied in computer-aided diagnosis systems for large-scale screening programs. Despite several segmentation and tracking methods proposed in the literature, there still exist several limitations specifically when two or more curvilinear structures cross or bifurcate, or in the presence of interrupted lines or highly curved blood vessels. In this paper, we propose a novel approach based on multi-orientation scores augmented with a contextual affinity matrix, which both are inspired by the geometry of the primary visual cortex (V1) and their contextual connections...
October 9, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
https://www.readbyqxmd.com/read/28983610/network-centrality-in-patients-with-acute-unilateral-open-globe-injury-a-voxel%C3%A2-wise-degree-centrality-study
#10
Hua Wang, Ting Chen, Lei Ye, Qi-Chen Yang, Rong Wei, Ying Zhang, Nan Jiang, Yi Shao
The present study aimed to investigate functional networks underlying brain‑activity alterations in patients with acute unilateral open globe injury (OGI) and associations with their clinical features using the voxel‑wise degree centrality (DC) method. In total, 18 patients with acute OGI (16 males and 2 females), and 18 healthy subjects (16 males and 2 females), closely matched in age, sex and education, participated in the present study. Each subject underwent a resting‑state functional magnetic resonance imaging scan...
September 26, 2017: Molecular Medicine Reports
https://www.readbyqxmd.com/read/28983243/long-term-visuo-gustatory-appetitive-and-aversive-conditioning-potentiate-human-visual-evoked-potentials
#11
Gert R J Christoffersen, Jakob L Laugesen, Per Møller, Wender L P Bredie, Todd R Schachtman, Christina Liljendahl, Ida Viemose
Human recognition of foods and beverages are often based on visual cues associated with flavors. The dynamics of neurophysiological plasticity related to acquisition of such long-term associations has only recently become the target of investigation. In the present work, the effects of appetitive and aversive visuo-gustatory conditioning were studied with high density EEG-recordings focusing on late components in the visual evoked potentials (VEPs), specifically the N2-P3 waves. Unfamiliar images were paired with either a pleasant or an unpleasant juice and VEPs evoked by the images were compared before and 1 day after the pairings...
2017: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/28975858/still-wanted-a-reproducible-demonstration-of-a-genuine-c1-attention-effect
#12
Michael A Pitts, Steven A Hillyard
Slotnick (this issue) has specified a number of experimental parameters that appear critical for enabling an attention-related modulation of the C1 component. These include stimulus presentation in the upper visual field, the presence of distractors, a high perceptual or attentional load, and measurements at midline occipito-parietal sites. While we agree with many of these recommendations, we would modify others and even dispute a few. Despite the employment of these parameters in a few existing studies, there has not yet been a convincing, reproducible demonstration of a modulation of the C1 component by spatial attention that can be localized to primary visual cortex...
October 4, 2017: Cognitive Neuroscience
https://www.readbyqxmd.com/read/28973563/nonlinear-dynamics-of-cortical-responses-to-color-in-the-human-cvep
#13
Valerie Nunez, Robert M Shapley, James Gordon
The main finding of this paper is that the human visual cortex responds in a very nonlinear manner to the color contrast of pure color patterns. We examined human cortical responses to color checkerboard patterns at many color contrasts, measuring the chromatic visual evoked potential (cVEP) with a dense electrode array. Cortical topography of the cVEPs showed that they were localized near the posterior electrode at position Oz, indicating that the primary cortex (V1) was the major source of responses. The choice of fine spatial patterns as stimuli caused the cVEP response to be driven by double-opponent neurons in V1...
September 1, 2017: Journal of Vision
https://www.readbyqxmd.com/read/28970785/multiple-transmitter-receptors-in-regions-and-layers-of-the-human-cerebral-cortex
#14
Karl Zilles, Nicola Palomero-Gallagher
We measured the densities (fmol/mg protein) of 15 different receptors of various transmitter systems in the supragranular, granular and infragranular strata of 44 areas of visual, somatosensory, auditory and multimodal association systems of the human cerebral cortex. Receptor densities were obtained after labeling of the receptors using quantitative in vitro receptor autoradiography in human postmortem brains. The mean density of each receptor type over all cortical layers and of each of the three major strata varies between cortical regions...
2017: Frontiers in Neuroanatomy
https://www.readbyqxmd.com/read/28966979/developmental-disruption-of-gabaar-meditated-inhibition-in-cntnap2-ko-mice
#15
Morgan S Bridi, Su Mi Park, Shiyong Huang
GABA released from presynaptic sites induces short-lived phasic inhibition mediated by synaptic GABAA receptors (GABAARs) and longer-duration tonic inhibition mediated by extrasynaptic GABAA or GABAB receptors (GABABRs). A number of studies have found that contactin-associated protein 2 (Cntnap2) knockout (KO) mice, a well-established mouse model of autism, exhibit reduced interneuron numbers and aberrant phasic inhibition. However, little is known about whether tonic inhibition is disrupted in Cntnap2 KO mice and when the disruption of inhibition begins to occur during postnatal development...
September 2017: ENeuro
https://www.readbyqxmd.com/read/28965507/thalamocortical-processing-in-vision
#16
Reece Mazade, Jose Manuel Alonso
Visual information reaches the cerebral cortex through a major thalamocortical pathway that connects the lateral geniculate nucleus (LGN) of the thalamus with the primary visual area of the cortex (area V1). In humans, ∼3.4 million afferents from the LGN are distributed within a V1 surface of ∼2400 mm2, an afferent number that is reduced by half in the macaque and by more than two orders of magnitude in the mouse. Thalamocortical afferents are sorted in visual cortex based on the spatial position of their receptive fields to form a map of visual space...
January 2017: Visual Neuroscience
https://www.readbyqxmd.com/read/28964930/grasping-with-a-new-hand-improved-performance-and-normalized-grasp-selective-brain-responses-despite-persistent-functional-changes-in-primary-motor-cortex-and-low-level-sensory-and-motor-impairments
#17
Kenneth F Valyear, Daniela Mattos, Benjamin A Philip, Christina Kaufman, Scott H Frey
Hand loss can now be reversed through surgical transplantation years or decades after amputation. Remarkably, these patients come to use their new hand to skilfully grasp and manipulate objects. The brain mechanisms that make this possible are unknown. Here we test the hypothesis that the anterior intraparietal cortex (aIPC) - a multimodal region implicated in hand preshaping and error correction during grasping - plays a key role in this compensatory grasp control. Motion capture and fMRI are used to characterize hand kinematics and brain responses during visually guided grasping with a transplanted hand at 26 and 41 months post-transplant in patient DR, a former hand amputee of 13 years...
September 28, 2017: NeuroImage
https://www.readbyqxmd.com/read/28963811/altered-white-matter-structure-in-the-visual-system-following-early-monocular-enucleation
#18
Nikita A Wong, Sara A Rafique, Krista R Kelly, Stefania S Moro, Brenda L Gallie, Jennifer K E Steeves
Partial visual deprivation from early monocular enucleation (the surgical removal of one eye within the first few years of life) results in a number of long-term morphological adaptations in adult cortical and subcortical visual, auditory, and multisensory brain regions. In this study, we investigated whether early monocular enucleation also results in the altered development of white matter structure. Diffusion tensor imaging and probabilistic tractography were performed to assess potential differences in visual system white matter in adult participants who had undergone early monocular enucleation compared to binocularly intact controls...
September 30, 2017: Human Brain Mapping
https://www.readbyqxmd.com/read/28961524/auditory-attention-enhances-processing-of-positive-and-negative-words-in-inferior-and-superior-prefrontal-cortex
#19
Martin Wegrzyn, Cornelia Herbert, Thomas Ethofer, Tobias Flaisch, Johanna Kissler
Visually presented emotional words are processed preferentially and effects of emotional content are similar to those of explicit attention deployment in that both amplify visual processing. However, auditory processing of emotional words is less well characterized and interactions between emotional content and task-induced attention have not been fully understood. Here, we investigate auditory processing of emotional words, focussing on how auditory attention to positive and negative words impacts their cerebral processing...
September 6, 2017: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
https://www.readbyqxmd.com/read/28958900/effects-of-3-week-total-meal-replacement-vs-typical-food-based-diet-on-human-brain-functional-magnetic-resonance-imaging-food-cue-reactivity-and-functional-connectivity-in-people-with-obesity
#20
Chanaka Nadeeshan Kahathuduwa, Tyler Davis, Michael O'Boyle, Lori Ann Boyd, Shao-Hua Chin, Dmitrii Paniukov, Martin Binks
OBJECTIVES: Calorie restriction via total meal replacement (TMR) results in greater reduction of food cravings compared to reduced-calorie typical diet (TD). Direct evidence of the impact of these interventions on human brain fMRI food-cue reactivity (fMRI-FCR) and functional connectivity is absent. We examined the effects of a 3-week 1120 kcal/d TMR intervention as compared to an iso-caloric TD intervention using an fMRI-FCR paradigm. METHODS: Thirty-two male and female subjects with obesity (19-60 years; 30-39...
September 25, 2017: Appetite
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