Spatial Relationships among Three Columnar Systems in Cat Area 17

Hübener, Mark; Shoham, Doron; Grinvald, Amiram; Bonhoeffer, Tobias

doi:10.1523/jneurosci.17-23-09270.1997

Cited by 333 publications

(322 citation statements)

References 61 publications

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“…3: (i) orientation preference is organized mostly radially, around a point of singularity in a pinwheel like fashion; (ii) pinwheels were found to rotate clockwise (CW) (white) and counterclockwise (CCW) (black) (see also Movies 1 and 2); and (iii) iso-orientation lines (linear zones), regions where orienta- tion preferences change slowly, tend to prefer to cross ODC borders closer to perpendicular orientations rather than parallel. Animal findings have also reported similar tendencies (30,31). The number of pinwheel centers per spatial area (pinwheel density) was 2.24/mm 2 (eccentricity, 5°), with an average column width (defined as Ϯ15°around 0°, 45°, 90°, or 135°orientations) of 0.77 Ϯ 0.13 mm and a spacing of 1.43 Ϯ 0.12 mm for subject 1, and 1.6/mm 2 (eccentricity, 8°) with an average column width of 0.86 Ϯ 0.13 mm and a spacing of 1.84 Ϯ 0.15 mm in subject 2.…”

Section: Resultssupporting

confidence: 53%

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High-field fMRI unveils orientation columns in humans

Yacoub

Harel

Uğurbil

2008

Proc. Natl. Acad. Sci. U.S.A.

535

492

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Functional (f)MRI has revolutionized the field of human brain research. fMRI can noninvasively map the spatial architecture of brain function via localized increases in blood flow after sensory or cognitive stimulation. Recent advances in fMRI have led to enhanced sensitivity and spatial accuracy of the measured signals, indicating the possibility of detecting small neuronal ensembles that constitute fundamental computational units in the brain, such as cortical columns. Orientation columns in visual cortex are perhaps the best known example of such a functional organization in the brain. They cannot be discerned via anatomical characteristics, as with ocular dominance columns. Instead, the elucidation of their organization requires functional imaging methods. However, because of insufficient sensitivity, spatial accuracy, and image resolution of the available mapping techniques, thus far, they have not been detected in humans. Here, we demonstrate, by using highfield (7-T) fMRI, the existence and spatial features of orientationselective columns in humans. Striking similarities were found with the known spatial features of these columns in monkeys. In addition, we found that a larger number of orientation columns are devoted to processing orientations around 90°(vertical stimuli with horizontal motion), whereas relatively similar fMRI signal changes were observed across any given active column. With the current proliferation of high-field MRI systems and constant evolution of fMRI techniques, this study heralds the exciting prospect of exploring unmapped and/or unknown columnar level functional organizations in the human brain.blood oxygen level-dependent contrast ͉ cortical map ͉ high resolution ͉ spin echo ͉ 7-tesla H igh-field MRI has pushed the level of detail to which submillimeter functional organizations can be mapped with fMRI because of increases in the signal-to-noise ratio (1) and the spatial accuracy of the functional signals (2). These gains are of critical importance because in the mammalian cortex, small functional cortical units that are repeated several times throughout a cortical area appear to constitute fundamental units of computation (3) that underlie mechanisms operative in brain function. One example of these fundamental units is cortical columns, a cluster of neurons with similar functional preferences spanning from the pial surface to the white matter. To no surprise, since their discovery in the somatosensory cortex (4), cortical columns have been identified across the cortex (5) and investigated in great detail (4, 6-8). In the visual cortex, preference to the right or left eye (ocular dominance), direction of motion, spatial frequency, and orientation have all been characterized (9-15). In humans, the first and, to date, the only example of such functional domains ever to have been identified is ocular dominance columns (ODCs). These were first observed by using anatomical staining techniques in the postmortem human brain of subjects who had lost sight in one eye (16). They were foun...

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Section: Resultssupporting

confidence: 53%

“…Animal model studies have described several general features in the spatial organization of each map and their interdependence (30)(31)(32). These features serve as a test for the veracity of the maps obtained in the human brain in the present study.…”

Section: Resultsmentioning

confidence: 88%

High-field fMRI unveils orientation columns in humans

Yacoub

Harel

Uğurbil

2008

Proc. Natl. Acad. Sci. U.S.A.

535

492

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“…The rest of the synaptic drive to simple cells derives from the cortex. In fact, considering the multitude of other stimulus features that are computed by V1 neurons [33], as well as the modulatory and feedback projections that V1 receives, it is impressive that V1 neurons are generally so sharply tuned at all.…”

Section: Generation Vs Maintenance Of Tuningmentioning

confidence: 99%

Local networks in visual cortex and their influence on neuronal responses and dynamics

Schummers¹,

Mariño²,

Sur³

2004

Journal of Physiology-Paris

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Networks of neurons in the cerebral cortex generate complex outputs that are not simply predicted by their inputs. These emergent responses underlie the function of the cortex. Understanding how cortical networks carry out such transformations requires a description of the responses of individual neurons and of their networks at multiple levels of analysis. We focus on orientation selectivity in primary visual cortex as a model system to understand cortical network computations. Recent experiments in our laboratory and others provide significant insight into how cortical networks generate and maintain orientation selectivity. We first review evidence for the diversity of orientation tuning characteristics in visual cortex. We then describe experiments that combine optical imaging of orientation maps with intracellular and extracellular recordings from individual neurons at known locations in the orientation map. The data indicate that excitatory and inhibitory synaptic inputs are summed across the cortex in a manner that is consistent with simple rules of integration of local inputs. These rules arise from known anatomical projection patterns in visual cortex. We propose that the generation and plasticity of orientation tuning is strongly influenced by local cortical networks-the diversity of these properties arises in part from the diversity of neighbourhood features that derive from the orientation map.

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“…Extensive electrophysiological recordings (12-17) and optical-imaging experiments have not provided a consistent picture of SF layout. The situation can be further complicated if variations in the temporal properties of the stimuli are included (18).One series of optical-imaging studies (7,(19)(20)(21)(22) advanced the viewpoint that the orientation layout of V1 is organized into high-and low-SF preference columns. From this view, it follows that only a single map is needed to characterize SF.…”

mentioning

confidence: 99%

“…One series of optical-imaging studies (7,(19)(20)(21)(22) advanced the viewpoint that the orientation layout of V1 is organized into high-and low-SF preference columns. From this view, it follows that only a single map is needed to characterize SF.…”

mentioning

confidence: 99%

The organization of orientation and spatial frequency in primary visual cortex

Sirovich

Uglesich²

2004

Proc. Natl. Acad. Sci. U.S.A.

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Many studies have demonstrated that the primary visual cortex contains multiple functional maps of visual properties (e.g., ocular dominance, orientation preference, and spatial-frequency preference), but as yet no consistent picture has emerged as to how these maps are related to one another. Three divergent, prior opticalimaging studies of spatial frequency are reanalyzed and critiqued in this article. Evidence is presented that a nonstimulus-specific response biased the interpretation of results in previous studies. In addition to reexamining four prior cat experiments, we carried out one new experiment. Through the use of different methods and a careful removal of the nonspecific response, we are led in all instances to a unique view of cortical organization for spatialfrequency preference. In particular, we find little apparent evidence for a columnar organization for spatial frequency. The response recorded by each image pixel may be viewed as arising from an admixture of low-and high-spatial-frequency populations. For most pixels, the ratio of these populations is 1:1.optical imaging ͉ nonspecific response ͉ generalized indicator ͉ function analysis T he retinotopic map relates an element of visual space to an element of cortical tissue. Neurons in the primary visual cortex are known to be differentially sensitive to orientation, , and spatial frequency (SF), k, of corresponding image elements that appear in visual space. ‡ Thus, it may be said that the primary visual cortex maps visual space through a local Fourier analysis (1, 2). The process by which this mapping takes place, although not fully understood, is known to involve information processing by the retina, lateral geniculate nucleus (LGN), and primary visual cortex area V1 (V1) and feedback from higher areas.Casting aside the nature of neuronal circuitry, the functional layout of the primary visual cortex is well established for orientation preference and ocular dominance. Anatomical (3-5) and optical-imaging (6-9) studies have elaborated and extended the columnar view of V1 that emerged from electrophysiology (10, 11). Less can be said of the representation of SF. Extensive electrophysiological recordings (12-17) and optical-imaging experiments have not provided a consistent picture of SF layout. The situation can be further complicated if variations in the temporal properties of the stimuli are included (18).One series of optical-imaging studies (7,(19)(20)(21)(22) advanced the viewpoint that the orientation layout of V1 is organized into high-and low-SF preference columns. From this view, it follows that only a single map is needed to characterize SF. This map contains regions corresponding to high and low SF with opposite signs. Thus high-and low-SF stimuli result in responses of opposite signatures. An obvious shortcoming is that intermediate SF would lead to null or near-null results. On the other hand, Everson et al. (23) reported that SF preference is continuously distributed and that at least two maps are required to depict SF represen...

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Spatial Relationships among Three Columnar Systems in Cat Area 17

Cited by 333 publications

References 61 publications

High-field fMRI unveils orientation columns in humans

High-field fMRI unveils orientation columns in humans

Local networks in visual cortex and their influence on neuronal responses and dynamics

The organization of orientation and spatial frequency in primary visual cortex

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