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Showing papers on "Orientation column published in 2016"


Journal ArticleDOI
05 May 2016-Nature
TL;DR: All main features of visual cortical topography, including orientation, direction and retinal disparity, follow a common organizing principle that arranges thalamic axons with similar retinotopy and ON–OFF polarity in neighbouring cortical regions.
Abstract: The primary visual cortex contains a detailed map of the visual scene, which is represented according to multiple stimulus dimensions including spatial location, ocular dominance and stimulus orientation. The maps for spatial location and ocular dominance arise from the spatial arrangement of thalamic afferent axons in the cortex. However, the origins of the other maps remain unclear. Here we show that the cortical maps for orientation, direction and retinal disparity in the cat (Felis catus) are all strongly related to the organization of the map for spatial location of light (ON) and dark (OFF) stimuli, an organization that we show is OFF-dominated, OFF-centric and runs orthogonal to ocular dominance columns. Because this ON-OFF organization originates from the clustering of ON and OFF thalamic afferents in the visual cortex, we conclude that all main features of visual cortical topography, including orientation, direction and retinal disparity, follow a common organizing principle that arranges thalamic axons with similar retinotopy and ON-OFF polarity in neighbouring cortical regions.

123 citations


Journal ArticleDOI
TL;DR: The results suggest that orientation selectivity of mouse V1 may not simply be inherited from LGN inputs, but could also depend on thalamocortical or V1 circuits.
Abstract: It has been debated whether orientation selectivity in mouse primary visual cortex (V1) is derived from tuned lateral geniculate nucleus (LGN) inputs or computed from untuned LGN inputs. However, few studies have measured orientation tuning of LGN axons projecting to V1. We measured the response properties of mouse LGN axons terminating in V1 and found that LGN axons projecting to layer 4 were generally less tuned for orientation than axons projecting to more superficial layers of V1. We also found several differences in response properties between LGN axons and V1 neurons in layer 4. These results suggest that orientation selectivity of mouse V1 may not simply be inherited from LGN inputs, but could also depend on thalamocortical or V1 circuits.

79 citations


Journal ArticleDOI
20 Oct 2016
TL;DR: A combination of physiological, anatomical, and theoretical studies has shed some light on the circuitry components necessary for generating orientation selectivity in V1.
Abstract: The mechanisms underlying the emergence of orientation selectivity in the visual cortex have been, and continue to be, the subjects of intense scrutiny. Orientation selectivity reflects a dramatic change in the representation of the visual world: Whereas afferent thalamic neurons are generally orientation insensitive, neurons in the primary visual cortex (V1) are extremely sensitive to stimulus orientation. This profound change in the receptive field structure along the visual pathway has positioned V1 as a model system for studying the circuitry that underlies neural computations across the neocortex. The neocortex is characterized anatomically by the relative uniformity of its circuitry despite its role in processing distinct signals from region to region. A combination of physiological, anatomical, and theoretical studies has shed some light on the circuitry components necessary for generating orientation selectivity in V1. This targeted effort has led to critical insights, as well as controversies, concerning how neural circuits in the neocortex perform computations.

73 citations


Journal ArticleDOI
TL;DR: The findings support the conclusion that radial bias is not necessary for orientation decoding, and highlight potential limitations of using temporal phase-encoded fMRI designs for characterizing voxel tuning properties.

39 citations


Journal ArticleDOI
TL;DR: Investigating axonal projections found that the somatosensory whisker cortex and the visual cortex directly innervated frontal cortex, with visual cortex axons innervating a region medial and posterior to the innervation from somatoensory cortex, consistent with the location of sensory responses in frontal cortex.
Abstract: The spatial organization of mouse frontal cortex is poorly understood. Here, we used voltage-sensitive dye to image electrical activity in the dorsal cortex of awake head-restrained mice. Whisker-deflection evoked the earliest sensory response in a localized region of primary somatosensory cortex and visual stimulation evoked the earliest responses in a localized region of primary visual cortex. Over the next milliseconds, the initial sensory response spread within the respective primary sensory cortex and into the surrounding higher order sensory cortices. In addition, secondary hotspots in the frontal cortex were evoked by whisker and visual stimulation, with the frontal hotspot for whisker deflection being more anterior and lateral compared to the frontal hotspot evoked by visual stimulation. Investigating axonal projections, we found that the somatosensory whisker cortex and the visual cortex directly innervated frontal cortex, with visual cortex axons innervating a region medial and posterior to the innervation from somatosensory cortex, consistent with the location of sensory responses in frontal cortex. In turn, the axonal outputs of these two frontal cortical areas innervate distinct regions of striatum, superior colliculus, and brainstem. Sensory input, therefore, appears to map onto modality-specific regions of frontal cortex, perhaps participating in distinct sensorimotor transformations, and directing distinct motor outputs.

26 citations


Journal ArticleDOI
TL;DR: The threshold difference seen for parallel and perpendicular gratings suggests the use of two oblique gratings as stimuli in alternative forced-choice procedures for peripheral vision evaluation to reduce measurement variation.
Abstract: Peripheral visual evaluations are important in many aspects of vision care and research. One instance is central visual field loss, where the visual evaluation has to be performed in the eccentric preferred retinal locus.1–3 Peripheral evaluation is challenging because of reduced retinal function and large optical errors. Care must therefore be taken when designing the psychophysical procedure to avoid additional uncertainties in the estimated threshold. Spatial visual acuity in the periphery is known to vary with task (resolution or detection),4–6 field loci (eccentricity and meridian), 7–9 and stimulus properties (orientation of the stimulus).7–11 For accurate visual evaluation, all three factors should be taken into consideration. However, little is known about the interaction between task and stimulus orientation. In this study, we therefore quantify the difference in detection and resolution thresholds for gratings of different orientations in the peripheral visual field. Peripheral resolution acuity is well known to be dependent on the orientation of the visual stimuli—known as the meridional effect. Several psychophysical and functional magnetic resonance imaging studies have found that stimuli oriented radially along the meridian are better resolved than stimuli oriented in other directions. 7–11 It has also been reported that the meridional preference for resolution is not caused by refractive errors or other aberrations, hence supporting neural origin.8,9 The physiological cause for the meridional preference would be that retinal ganglion cell dendritic fields are radially oriented.12–15 A neural selectivity for radial grating orientations also in cortical level has been confirmed by Schall et al.16 who found that the orientation columns in the visual cortex of cats are wider for the radial orientation than for other orientations. This neural orientation preference will increase the uncertainty and variability of threshold estimations if the alternatives of a forced-choice paradigm are orientated parallel and perpendicular to the meridian. In addition, there might be a response bias when one of the orientations is more easily seen than the others. Peripheral vision is very important for daily activities, such as orientation, movement, and driving. Peripheral vision evaluation is very important in cases such as macular degenerations, myopia development, and progression research. To avoid uncertainties and inaccuracies in the peripheral acuity measurements, appropriate stimuli selection is vital. Previous studies on the meridional effect have mainly focused on resolution acuity, and little is known about orientation preferences for peripheral detection acuity. Unlike central vision, there is a difference between resolution and detection acuity for peripheral vision: high-contrast resolution is relatively unaffected by optical errors because it is neurally limited,5,17 whereas detection is affected by optical errors.5,6 This means that a stimulus with a spatial frequency above the neural sampling limit cannot be resolved. However, the undersampled stimulus undergoes aliasing and can be perceived through its moire pattern with a lower spatial frequency, a lower contrast, and a different orientation.4,18 The zone of aliasing is dependent on the optical errors in the periphery. Correction of peripheral optical errors enhances the contrast, which improves detection acuity and thereby widens the aliasing zone. Because of the influence of optical errors on peripheral detection acuity, a meridional preference for detection tasks may be a combination of optical and neural orientation sensitivities. The amount and direction of asymmetric optical errors like astigmatism, coma, and transverse chromatic aberration (TCA) can favor the detection of certain orientations over others. The peripheral image quality is dominated by off-axis astigmatism and coma oriented radially, which could lead to poorer detection of perpendicular gratings and hence a larger meridional effect. To reveal neural limitations and evaluate whether the meridional effect is also present for detection tasks, correction of these optical errors is necessary. Therefore, the present study uses a combination of trial lenses, an adaptive optics system, and monochromatic stimuli to correct for the existing monochromatic and chromatic optical errors. In a peripheral detection study by Cheney et al.,19 the optical errors were surpassed by using circular windowed interferometric stimuli. The reported detection cutoff frequencies were high, and a large meridional preference was reported in white light and was suggested to be purely optical in origin, caused by TCA, as the effect disappeared in green light. However, these results may be caused by the special properties of the interferometric stimuli (such as high retinal image contrast and the presence of TCA in the absence of longitudinal chromatic aberrations), and the meridional preference for detection of noninterferometric stimuli could therefore be very different. In the present study, we evaluate the peripheral resolution and detection acuities for different orientations in different visual field meridians with optical correction. The detection measurements are also performed in monochromatic light to elude the effects of chromatic aberrations.

19 citations


Journal ArticleDOI
TL;DR: A neural network that can learn to perform a Hough Transform-like computation in an unsupervised manner is the main takeaway from this work.

11 citations


Journal ArticleDOI
TL;DR: By targeting the visual cortex exclusively, this work tested whether combined optimization of shape, coil placement, and electronics would yield the necessary gains in signal‐to‐noise ratio (SNR) for submillimeter visual cortex functional MRI (fMRI).
Abstract: Purpose Functional neuroimaging of small cortical patches such as columns is essential for testing computational models of vision, but imaging from cortical columns at conventional 3T fields is exceedingly difficult. By targeting the visual cortex exclusively, we tested whether combined optimization of shape, coil placement, and electronics would yield the necessary gains in signal-to-noise ratio (SNR) for submillimeter visual cortex functional MRI (fMRI). Method We optimized the shape of the housing to a population-averaged atlas. The shape was comfortable without cushions and resulted in the maximally proximal placement of the coil elements. By using small wire loops with the least number of solder joints, we were able to maximize the Q factor of the individual elements. Finally, by planning the placement of the coils using the brain atlas, we were able to target the arrangement of the coil elements to the extent of the visual cortex. Results The combined optimizations led to as much as two-fold SNR gain compared with a whole-head 32-channel coil. This gain was reflected in temporal SNR as well and enabled fMRI mapping at 0.75 mm resolutions using a conventional GRAPPA-accelerated gradient echo echo planar imaging. Conclusion Integrated optimization of shape, electronics, and element placement can lead to large gains in SNR and empower submillimeter fMRI at 3T. Magn Reson Med, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

10 citations


Journal ArticleDOI
TL;DR: The results suggest that temporal coherence of hemodynamic signals measured by optical imaging of intrinsic signals exists at a submillimeter columnar scale in resting state, suggesting that thestrength of resting connectivity is related to the strength of the visual stimulation response.
Abstract: Resting-state functional magnetic resonance imaging has been increasingly used for examining connectivity across brain regions. The spatial scale by which hemodynamic imaging can resolve functional connections at rest remains unknown. To examine this issue, deoxyhemoglobin-weighted intrinsic optical imaging data were acquired from the visual cortex of lightly anesthetized ferrets. The neural activity of orientation domains, which span a distance of 0.7–0.8 mm, has been shown to be correlated during evoked activity and at rest. We performed separate analyses to assess the degree to which the spatial and temporal characteristics of spontaneous hemodynamic signals depend on the known functional organization of orientation columns. As a control, artificial orientation column maps were generated. Spatially, resting hemodynamic patterns showed a higher spatial resemblance to iso-orientation maps than artificially generated maps. Temporally, a correlation analysis was used to establish whether iso-orien...

8 citations


Journal ArticleDOI
TL;DR: It was found that area 7 feedbacks mainly to areas 17 and 18 on ipsilateral hemisphere, and histological feedback pattern from area 7 to area 17 is weblike.

8 citations


Posted ContentDOI
17 Aug 2016-bioRxiv
TL;DR: It is demonstrated that the orientation selectivity of neurons in primary visual cortex of mouse is highly dependent on the stimulus SF and it is proposed that a receptive-field model of a 2D asymmetric Gabor, rather than a symmetric one, can explain this dependence.
Abstract: The response properties of neurons to sensory stimuli have been used to identify their receptive fields and functionally map sensory systems. In primary visual cortex, most neurons are selective to a particular orientation and spatial frequency of the visual stimulus. Using two-photon calcium imaging of neuronal populations from the primary visual cortex of mice, we have characterized the response properties of neurons to various orientations and spatial frequencies. Surprisingly, we found that the orientation selectivity of neurons actually depends on the spatial frequency of the stimulus. This dependence can be easily explained if one assumed spatially asymmetric Gabor-type receptive fields. We propose that receptive fields of neurons in layer 2/3 of visual cortex are indeed spatially asymmetric, and that this asymmetry could be used effectively by the visual system to encode natural scenes.

Book ChapterDOI
01 Jan 2016
TL;DR: It is concluded that visual callosal connections are more similar to intrinsic connections and can be interpreted as extending this circuit across the hemispheres by comparing data from lateral and feedback circuits.
Abstract: Anatomy and function of long-range intrinsic and callosal axons in primary visual cortex are reviewed. In cats, both arborize in a patchy manner, in an orderly relationship to the visuotopic map and visual stimulus features. Patches tend to link neurons with similar contour and direction preference aligned along a collinear visual field axis. Direct investigation of callosal action on visual responses reveals a multiplicative shift without changing neuronal selectivity. Both gain and bias toward excitation or inhibition depend on global stimulus attributes. Interactions are more pronounced for neurons processing similar, in particular cardinal, visual features. As feature selectivity emerges already in ongoing neuronal activity, it is hypothesized that perceptual grouping is anticipated via the feature bias in patchy connections. By comparing data from lateral and feedback circuits, we conclude that visual callosal connections are more similar to intrinsic connections and can be interpreted as extending this circuit across the hemispheres.

Book ChapterDOI
01 Jan 2016
TL;DR: Clinical considerations with regards to diseases of the visual system include Leber’s hereditary optic neuropathy that affects the retinal ganglion cells; degenerative illness affecting the primary visual cortex as well as other areas of cerebral cortex include Lewy body dementia.
Abstract: In order to understand the organization of visual spatial organization within the occipital cortex, it is necessary to review basic functional aspects of the retina and its projection to the lateral geniculate. Retinal photoreceptors actually hyperpolarize when light hits the 11-cis retinal molecule and induces molecular motion within the photoreceptor membrane from the isomerization into all-trans retinal; constant fine microsaccades of the eye prevent extinction of the visual pigments. The output for the temporal half of each retina joins with the same for the nasal hemi-retina from the opposite eye to unite at the optic chiasm and project back to innervate the laminated lateral geniculate body of the thalamus, where the optic radiations are formed which sweep back around the occipital horns of the lateral ventricles to reach the primary occipital cortex. Ocular dominance columns form a basic organizational theme to the occipital cortex, where serpiginous strips from one eye alternate with the same for the other eye. Superimposed on this anatomic parcelization are functional columns tuned for orientation of the visual stimulus where neurons selectively fire according to the angle of movement yet other showing more complex properties of selectively firing according to sharp changes in contrast (edge detection). Clinical considerations with regards to diseases of the visual system include Leber’s hereditary optic neuropathy that affects the retinal ganglion cells; degenerative illness affecting the primary visual cortex as well as other areas of cerebral cortex include Lewy body dementia. With regards to migraine, posterior waves of spreading depression affecting the occipital cortex generate migrainous visual symptoms in advance of the typically severe, debilitating headache.

Posted ContentDOI
10 Jan 2016-bioRxiv
TL;DR: It is shown that opposite orientation preferences are present and replicable within small V1 patches within a quarterfield representation, demonstrating that fine-grained fMRI patterns contribute to the orientation information present in fMRI data.
Abstract: The orientation of a visual grating can be decoded from human primary visual cortex (V1) using functional magnetic resonance imaging (fMRI) at conventional resolutions (2-3 mm voxel width, 3T scanner). It is unclear to what extent this information originates from different spatial scales of neuronal selectivity, ranging from orientation columns to global areal maps. According to the global-areal-map account, fMRI orientation decoding relies exclusively on fMRI voxels in V1 exhibiting a radial or vertical preference. Here we show, by contrast, that 2-mm isotropic voxels in a small patch of V1 within a quarterfield representation exhibit reliable opposite selectivities. Sets of voxels with opposite selectivities are locally intermingled and each set can support orientation decoding. This indicates that global areal maps cannot fully account for orientation information in fMRI and demonstrates that fMRI also reflects fine-grained patterns of neuronal selectivity.

Journal ArticleDOI
TL;DR: Differences in orientation tuning for non‐preferred vs. preferred directions were smallest in layer 4 and largest in layer 6, consistent with a non‐linear process of intra‐cortical inhibition that enhances DS by selective suppression of neuronal firing for non-preferred directions of stimulus motion in a lamina‐dependent manner.
Abstract: Neurons in the visual cortex are generally selective to direction of movement of a stimulus. Although models of this direction selectivity (DS) assume linearity, experimental data show stronger degrees of DS than those predicted by linear models. Our current study was intended to determine the degree of non-linearity of the DS mechanism for cells within different laminae of the cat's primary visual cortex. To do this, we analysed cells in our database by using neurophysiological and histological approaches to quantify non-linear components of DS in four principal cortical laminae (layers 2/3, 4, 5, and 6). We used a DS index (DSI) to quantify degrees of DS in our sample. Our results showed laminar differences. In layer 4, the main thalamic input region, most neurons were of the simple type and showed high DSI values. For complex cells in layer 4, there was a broad distribution of DSI values. Similar features were observed in layer 2/3, but complex cells were dominant. In deeper layers (5 and 6), DSI value distributions were characterized by clear peaks at high values. Independently of specific lamina, high DSI values were accompanied by narrow orientation tuning widths. Differences in orientation tuning for non-preferred vs. preferred directions were smallest in layer 4 and largest in layer 6. These results are consistent with a non-linear process of intra-cortical inhibition that enhances DS by selective suppression of neuronal firing for non-preferred directions of stimulus motion in a lamina-dependent manner. Other potential mechanisms are also considered.

Journal ArticleDOI
TL;DR: Using orientation columns as a paradigm, it is suggested that repulsive shifts are essentially fundamental to preserve the functional organization of the cortex, and thus, maintaining the functional homeostasis of the brain.
Abstract: Brain is phenomenally plastic and exhibits this capacity well into adulthood. Neuronal plasticity can be studied by using different adaptation protocols. Post-adaptation neurons typically show attractive and repulsive shifts even though challenged by the same adapter. Using orientation columns as a paradigm, we argue and suggest that repulsive shifts are essentially fundamental to preserve the functional organization of the cortex, and thus, maintaining the functional homeostasis of the brain.