scholarly journals Representation of Cardinal Contour Overlaps Less With Representation of Nearby Angles in Cat Visual Cortex

2003 ◽  
Vol 90 (6) ◽  
pp. 3912-3920 ◽  
Author(s):  
Gang Wang ◽  
Shan Ding ◽  
Kazutomo Yunokuchi
Keyword(s):  
Cortical Area ◽  
Statistical Significance ◽  
Central Area ◽  
Population Level ◽  
Orientation Tuning ◽  
Cell Populations ◽  
Area 17 ◽  
Optical Signals ◽  
Adult Cats ◽  
Degree Of Overlap

Extensive attempts have been made to explain the neurobiological basis of the greater sensitivity of the visual system to vertically or horizontally oriented information than to information presented at oblique angles. However, investigators have largely ignored the overlap of the representation of a given angle with the representation of nearby angles. Recordings based on intrinsic optical signals were obtained in area 17 from 12 adult cats during the presentation of contours in various orientations. A method investigating both amplitude and statistical significance of changes was proposed to evaluate the orientation tuning properties for cell populations in the central area retinotopically corresponding to 0–15° of visual field. Cardinal orientations were found to activate significantly greater areas in the exposed cortical area than the areas activated by oblique orientations. Areas activated by cardinal or oblique contours and those separated from them by 10° were compared. A significantly lower degree of overlap was seen between areas activated by presentation of cardinal contours and areas activated by neighboring orientations compared with those for oblique orientations which overlapped more extensively with neighboring orientations. In addition, areas activated only by cardinal contours were significantly larger than areas activated only by oblique contours. These results demonstrated in cell population level that more cells prefer horizontal or vertical orientations, and these cells are tuned more sharply than oblique selective cells.

Optical imaging of orientation and ocular dominance maps in area 17 of cats with convergent strabismus

2002 ◽  
Vol 19 (1) ◽  
pp. 39-49 ◽  
Author(s):  
RALF ENGELMANN ◽  
JOHN M. CROOK ◽  
SIEGRID LÖWEL
Keyword(s):  
Optical Imaging ◽  
Developmental Plasticity ◽  
Functional Organization ◽  
Ocular Dominance ◽  
Gene Pools ◽  
Area 17 ◽  
Intrinsic Signals ◽  
Functional Layout ◽  
Adult Cats ◽  
And Control

Strabismus (or squint) is both a well-established model for developmental plasticity of the brain and a frequent clinical symptom. While the layout and topographic relationship of functional domains in area 17 of divergently squinting cats has been analyzed extensively in recent years (e.g. Löwel et al., 1998), functional maps in convergently squinting animals have so far not been visualized with comparable detail. We have therefore investigated the functional organization of area 17 in adult cats with a surgically induced convergent squint angle. In these animals, visual acuity was determined by both behavioral tests and recordings of visual evoked potentials, and animals with comparable acuities in both eyes were selected for further experiments. The functional layout of area 17 was visualized using optical imaging of intrinsic signals. Monocular iso-orientation domains had a patchy appearance and their layout was different for left and right eye stimulation, so that segregated ocular dominance domains could be visualized. Iso-orientation domains exhibited a pinwheel-like organization, as previously described for normal and divergently squinting cats. Mean pinwheel density was the same in the experimental and control animals (3.4 pinwheel centers per mm2 cortical surface), but significantly (P < 0.00001) higher than that reported previously for normal and divergently squinting cats (2.7/mm2). A comparison of orientation with ocular dominance maps revealed that iso-orientation domains were continuous across the borders of ocular dominance domains and tended to intersect these borders at steep angles. However, in contrast to previous reports in normally raised cats, orientation pinwheel centers showed no consistent topographical relationship to the peaks of ocular dominance domains. Taken together, these observations indicate an overall similarity between the functional layout of orientation and ocular dominance maps in area 17 of convergently and divergently squinting cats. The higher pinwheel densities compared with previous reports suggest that animals from different gene pools might generally differ in this parameter and therefore also in the space constants of their cortical orientation maps.

Effects of Feedback Projections From Area 18 Layers 2/3 to Area 17 Layers 2/3 in the Cat Visual Cortex

1999 ◽  
Vol 82 (5) ◽  
pp. 2667-2675 ◽  
Author(s):  
Susana Martinez-Conde ◽  
Javier Cudeiro ◽  
Kenneth L. Grieve ◽  
Rosa Rodriguez ◽  
Casto Rivadulla ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Small Region ◽  
Orientation Tuning ◽  
Area 17 ◽  
Visual Responses ◽  
Area 18 ◽  
Cat Visual Cortex ◽  
Effects Of Feedback ◽  
Feedback Connections

In the absence of a direct geniculate input, area 17 cells in the cat are nevertheless able to respond to visual stimuli because of feedback connections from area 18. Anatomic studies have shown that, in the cat visual cortex, layer 5 of area 18 projects to layer 5 of area 17, and layers 2/3 of area 18 project to layers 2/3 of area 17. What is the specific role of these connections? Previous studies have examined the effect of area 18 layer 5 blockade on cells in area 17 layer 5. Here we examine whether the feedback connections from layers 2/3 of area 18 influence the orientation tuning and velocity tuning of cells in layers 2/3 of area 17. Experiments were carried out in anesthetized and paralyzed cats. We blocked reversibly a small region (300 μm radius) in layers 2/3 of area 18 by iontophoretic application of GABA and recorded simultaneously from cells in layers 2/3 of area 17 while stimulating with oriented sweeping bars. Area 17 cells showed either enhanced or suppressed visual responses to sweeping bars of various orientations and velocities during area 18 blockade. For most area 17 cells, orientation bandwidths remained unaltered, and we never observed visual responses during blockade that were absent completely in the preblockade condition. This suggests that area 18 layers 2/3 modulate visual responses in area 17 layers 2/3 without fundamentally altering their specificity.

Processing of form and motion in area 21a of cat visual cortex

1993 ◽  
Vol 10 (1) ◽  
pp. 93-115 ◽  
Author(s):  
B. Dreher ◽  
A. Michalski ◽  
R. H. T. Ho ◽  
C. W. F. Lee ◽  
W. Burke
Keyword(s):  
Spatial Organization ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Orientation Tuning ◽  
Area 17 ◽  
Horizontal Strip ◽  
Tuning Curves ◽  
Mean Width ◽  
Area 21A ◽  
The Mean

AbstractExtracellular recordings from single neurons have been made from presumed area 21a of the cerebral cortex of the cat, anesthetized with N2O/O2/sodium pentobarbitone mixture. Area 21a contains mainly a representation of a central horizontal strip of contralateral visual field about 5 deg above and below the horizontal meridian.Excitatory discharge fields of area 21a neurons were substantially (or slightly but significantly) larger than those of neurons at corresponding eccentricities in areas 17, 19, or 18, respectively. About 95% of area 21a neurons could be activated through either eye and the input from the ipsilateral eye was commonly dominant. Over 90% and less than 10% of neurons had, respectively, C-type and S-type receptive-field organization. Virtually all neurons were orientation-selective and the mean width at half-height of the orientation tuning curves at 52.9 deg was not significantly different from that of neurons in areas 17 and 18. About 30% of area 21a neurons had preferred orientations within 15 deg of the vertical.The mean direction-selectivity index (32.8%) of area 21a neurons was substantially lower than the indices for neurons in areas 17 or 18. Only a few neurons exhibited moderately strong end-zone inhibition. Area 21a neurons responded poorly to fast-moving stimuli and the mean preferred velocity at about 12.5 deg/s was not significantly different from that for area 17 neurons.Selective pressure block of Y fibers in contralateral optic nerve resulted in a small but significant reduction in the preferred velocities of neurons activated via the Y-blocked eye. By contrast, removal of the Y input did not produce significant changes in the spatial organization of receptive fields (S or C type), the size of the discharge fields, the width of orientation tuning curves, or direction-selectivity indices.Our results are consistent with the idea that area 21a receives its principal excitatory input from area 17 and is involved mainly in form rather than motion analysis.

Heterogeneity in local distributions of orientation-selective neurons in the cat primary visual cortex

1996 ◽  
Vol 13 (3) ◽  
pp. 509-516 ◽  
Author(s):  
Pedro E. Maldonado ◽  
Charles M. Gray
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Local Level ◽  
Spike Trains ◽  
Preferred Orientation ◽  
Orientation Tuning ◽  
Area 17 ◽  
Average Difference ◽  
Orientation Preference ◽  
Neuronal Spike Trains

AbstractWe have employed the tetrode technique, which allows accurate discrimination of individual neuronal spike trains from multiunit recordings, in order to examine the variation of orientation selectivity among local groups of neurons. We recorded a total of 321 cells from 62 sites in area 17 of halothane-anesthetized cats; each site contained between three to ten neurons that were estimated to be less than 65 μm away from the tetrode tip. For each cell, we determined the orientation tuning in response to moving bars. Of the cells tested, 8.4% were unresponsive, 22.7% had no preferential response to any particular orientation, while 68.8% were tuned. The average difference in preferred orientation between cell pairs recorded at the same site was 10.7 deg, but the variance in preferred orientation differences differed significantly among sites. Some clusters of cells exhibited the same or nearly the same orientation preference, while others had orientation preferences that differed by as much as 90 deg. Our data demonstrate that the tuning for orientation is more heterogeneously distributed at a local level than previous studies have suggested.

Quantitative Imaging of Femoral Bone Marrow Microenvironments Reveals a Heterogenous Distribution of Hematopoietic Stem and Progenitor Cells.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1455-1455
Author(s):  
Cesar Nombela-Arrieta ◽  
Brendan Harley ◽  
Gregory Pivarnik ◽  
John E Mahoney ◽  
Elena Levantini ◽  
...  
Keyword(s):  
Stem Cells ◽  
B Cells ◽  
Cell Biology ◽  
Conflicts Of Interest ◽  
Statistical Significance ◽  
Quantitative Imaging ◽  
Cell Types ◽  
Immunofluorescent Staining ◽  
Cell Populations ◽  
Hematopoietic Stem

Abstract Abstract 1455 Poster Board I-478 Sustained production of all mature blood cell types relies on the continuous proliferation and differentiation of a rare population of self-renewing, multipotent hematopoietic stem cells (HSCs). HSC maintenance and lineage differentiation are thought to be regulated by spatially confined niches, defined by cellular components, soluble regulators, and the extracellular matrix immediately surrounding stem cells. Identification of these microenvironments in which endogenous and transferred HSCs reside within the BM is a major challenge in stem cell biology with relevant clinical implications. Yet the extreme rarity of HSCs, their dynamic nature, and the lack of specific markers to identify them, have precluded an accurate definition of HSC niches to date. Quantitative imaging technologies such as Laser Scanning Cytometry (LSC) are designed for the automated analysis of large cell numbers at a single cell level with high resolution while preserving the morphological information lost in flow cytometry, therefore providing data of statistical significance even for rare cell populations such as HSCs. We have employed LSC to analyze the localization of both adoptively transferred and endogenous hematopoietic stem and progenitor cell (HSPC) populations inside whole longitudinal sections of murine femoral BM cavities. Our results indicate that, as previously suggested, purified HSPC (Lin−c-kit+Sca-1+) significantly accumulate in endosteal regions (ER) of BM cavities (within 100μm of inner bone surface) upon transplantation. Nevertheless, analysis of sufficient numbers of more differentiated cell subsets (Lin−c-kit+Sca-1− progenitors, pro B cells and mature B cells) indicated that these areas serve as homing sites for most hematopoietic cells, highlighting the limitations of any conclusions drawn on HSC niche identity from studies performed with transferred HSPC populations. Immunofluorescent staining of endogenous cell populations revealed a gradient in distribution of early hematopoietic progenitors (c-kit+), which accumulated in but were not restricted to ER regions. Of note, a vast majority (>80%) of HSPC (Bmi-GFPhic-kit+, or Lin−c-kit+Sca-1+),were found inside ER, although not directly adjacent to endosteal surfaces. Our studies define endosteal areas as tissue regions where HSPC reside in close proximity, but not necessarily in direct contact with a dense vascular network, osteoblastic cells and other potential niche cell types and growth factors currently under investigation. Disclosures No relevant conflicts of interest to declare.

Receptive field and orientation scatter studied by tetrode recordings in cat area 17

1999 ◽  
Vol 16 (4) ◽  
pp. 637-652 ◽  
Author(s):  
P.A. HETHERINGTON ◽  
N.V. SWINDALE
Keyword(s):  
Receptive Field ◽  
Field Size ◽  
Orientation Tuning ◽  
Small Contribution ◽  
Area 17 ◽  
Image Size ◽  
Degree Of Orientation ◽  
Smooth Map ◽  
Random Scatter ◽  
Field Position

The receptive-field positions and orientation preferences of neurons occupying the same tangential location in visual cortex are thought to be similar but to have an associated random scatter. However, previous estimates of this scatter may have been inflated by the use of subjective plotting methods, sequential recording of single units, and residual eye movements. Here we report measurements of receptive-field position and orientation scatter in cat area 17 made with tetrodes, which were able to simultaneously isolate and record up to 11 nearby neurons (ensembles). We studied 355 units at 72 sites with moving light and dark bars. Receptive-field sizes and positions were estimated by least-squares fitting of Gaussians to response profiles. We found that receptive-field position scatter was about half of the ensemble average receptive-field size. We confirmed previous estimates of orientation scatter, but calculations suggested that much of it may be accounted for by anatomical scatter in the positions of recorded neurons relative to the tetrode in a smooth map. Orientation tuning width was positively correlated with the degree of orientation scatter. Scatter was not independent in the two eyes: deviations from the local mean for both preferred orientation and receptive-field position were correlated although a significant amount of residual inter-ocular orientation and receptive-field position scatter was present. We conclude that cortical maps of orientation and receptive-field position are more ordered than was previously thought, and that random scatter in receptive-field positions makes a relatively small contribution to cortical point image size.

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