Feed-forward, feedback and lateral interactions in membrane potentials and spike trains from the visual cortex in vivo.

Neurons in the visual cortex receive input from the lateral geniculate nucleus (feed-forward), higher order visual areas (feedback) and local neurons in the surroundings (lateral interactions). Here we first briefly review the approximate timing and proportion of these three types of influences on the membrane potentials in visual areas 17, 18 and 19. Then we present original results from an independent component analysis of multiunit spike trains in the same visual areas to resolve the contribution from these three sources. We stimulated the visual cortex of the ferret with a small transient contrast square stimulus and recorded the multiunit activity in areas 17, 18 and 19 with single or multiple electrodes. The spike trains had three reproducible components having their maxima at 40, 55 and 105ms after the start of the presentation of the stimulus. The time course of the third component was significantly correlated with the population membrane potential in the supragranular layers of areas 17, 18 and 19. The first spike train component was interpreted as a feed-forward response, the second spike train component as driving the laterally spreading depolarization and the third spike train component as the firing caused by the lateral spreading- and the feedback depolarization.     

An overall description of retinotopic mapping in the cat's visual cortex areas 17, 18, and 19

Mathematical functions are derived which model the retinotopic mapping in the cat's visual cortical areas 17, 18, and 19. All three mappings are simple modifications of a complex power function with an exponent of 0.43. This function is decomposed so as to give an intermediate stage which is common to all three mappings and can be regarded as a model of the lateral geniculate nucleus mapping. The influence of retinotopic mapping on visual receptive fields was studied. The results show that a dependence of the receptive field properties on the position in the visual field is to be expected.     

Cortical neuronal connections and reconstruction of visual space

We investigated distribution of retrograde-labelled cells in cortical areas 17, 18, and the transition zone 17/18 of both hemispheres in cats after microiontophoretic horseradish peroxidase (HRP) injections into the single cortical columns of area 17, 18, 19 or 21a. On the base of clustered pattern of intrinsic labelling, asymmetric location of labelled callosal cells that was associated with the appropriate pattern of labelling in layers A and A1 of lateral geniculate nucleus, we suggest that cortical neuronal connections are eye-specific and may provide for each eye a separate binding of visual hemifields. After HRP injections into columns of area 19 or 21a, the disparate inputs from areas 17, 18 and transition zone 17/18 were revealed. Such connections may provide a local depth information and the selection of stereoscopic surfaces in central sectors of visual space.     

Structure of reciprocal connections in visual cortical areas 17 and 18 in cats

Single cortical columns of areas 17, 18 in the cat were microiontophoretically injected with horseradish peroxidase. Spatial and laminar distributions of retrogradell labelled cells in both areas were investigated. Following injections in area 17 or in area 18 the labelled cells' region in area 17 was elongated (in a tangential plane) along the representation of visual field horizontal meridian. However the labelled cells' region in area 18 was elongated along the representation of vertical meridian. Such projection patterns appear to be common in these cortical areas throughout the central 10 degrees on various elevations (from -40 degrees to +10 degrees) of the visual field representation. Thus the spatial arrangement of intrinsic and extrinsic connections in each area coincides, at the same time in area 17 they are orthogonal to area 18. The following visual information exchange scheme may be suggested. Area 17 may supply the area 18 with more detailed information on the horizontal component of the visual image, and in the opposite direction the information on the vertical component of the same image may be supplied.     

Projections of the cortical visual areas of the posterior gyrus sigmoid and the caudate nucleus in the cat

The complex performances of the visuo-motor system entail probably an intervention of circuits connecting, the primary visual areas, to other cortical regions, specially the sensory motor cortex, and certain sub-cortical formations. For testing this hypothesis, the unilateral resection of the areas 17, 18 and 19 has been undertaken on 19 cats, with delays ranging from 8 days to 3 months after intervention. The tracing of the pathways was carried out by combining different degenerating methods in particular the Marchi reaction. Based on this, it is possible to define a compact bundle of the axons originating from the primary visual cortex and dividing into two fascicles of unequal magnitude. The slender ends in the lower part of the posterior gyrus sigmo?d; the larger one penetrates into the caudale nucleus. An ultrastructural study specifies the modalities of distribution of the axons within this nucleus.     

Localization of human brain areas activated for chaotic and ordered pattern perception

The aim of our work was to localize cortical areas involved in the processing of incomplete figures using functional MRI (fMRI) for 8 healthy volunteers (18-30 year old) with the did of anatomical and fMRI fast imaging technique: echo planar imaging (EPI), whole brain scan (36 slices) matrix 64 x 64, 3.7 second. We used 1.5 T MR-scanner and BOLD-method (Blood Oxygenation Level Dependent), based on distinctions of magnetic properties of hemoglobin. Fast imaging technique on modern MR-scanners with > or = 1.5 T provides precise statistical maps of oxygenation increase with high spatial resolution. For test stimuli we used matrix of Gabor grating. We used two types of 10 x 10 matrices with chaotic and ordered orientation of Gabor gratings. The size, brightness and contrast of the stimuli were identical. The chaotic and ordered patterns activated different brain areas. We establish that ordered patterns activated only primary visual cortex - V1 and V2, (BA17-18), wheareas chaotic patterns activated in addition primary visual cortex, the V3,V4,V5 (BA19) of the occipital cortex and the area 7 of parietal area (BA7) classification. Decision making for that task is localized in prefrontal and frontal cortex, including (BA 6, 9, 10).     

Zur Informationsverarbeitung im visuellen System der Wirbeltiere. I

Summary In this paper it is tried to find a mathematical model for a number of mainly electrophysiological results concerning pattern recognition of mammals. The interpretations are essentially based on the experiments of Hubel and Wiesel in the visual system of the cat and the monkey.After a short introduction to the applied theory of linear nervous nets the investigations in the retina are interpreted. This part of the visual system can be considered as a bandpass-filter for space dependent oscillations. At the level of the geniculate body, a further filtering takes place which especially attenuates the low and the very high frequencies.The processes in the cortex regions 17, 18 and 19, where the further preprocessing of the pattern recognition takes place, can be interpreted by the theory of matched filters. In Area 17 the input pattern is reduced to the contour lines. In the two other areas the extraction of simple characteristic features such as line ends and corners takes place. By means of the present results it is not possible to draw complete conclusions on the structure of the recognition process.     

Parallel processing of binocular disparity in the cat's retinogeniculocortical pathways

In the cat, parallel streams of information processing have been traced from X-, Y- and W-type retinal ganglion cells to visual cortical areas 17 (X-, Y- and W-type), 18 (Y-type) and 19 (W-type). In the present study we have examined, in the anaesthetized and paralysed adult cat, the role played by X-, Y- and W-subsystems, projecting to areas 17 and 19, in the processing of binocular retinal disparity. The tapetal reflection technique was used to monitor residual eye movements and to provide a map, for each eye, of the retinal blood vessels which could later be compared with retinal wholemounts stained with cresyl violet to reveal the area centralis. The receptive-field disparities of cells recorded from areas 17 and 19 were compared with each other and with reference to the visual axes defined by the area centralis of each eye. Cells of area 19 (receiving W-type input) had horizontal receptive-field disparities that were significantly more divergent than those of the cells in area 17 and 17-18 'border region'. Referred to the area centralis, the mean horizontal receptive-field disparity in area 19 was -0.5 degrees (+/- 0.8 degrees). The mean horizontal receptive-field disparity of area 17 (receiving X-, Y- and W-type input) was convergent with respect to the visual axis at +2 degrees (+/- 0.5 degrees). Finally, the mean horizontal receptive-field disparity of the cells in the 17-18 border region (which receive mainly Y-type input) was even more convergent (2.6 degrees +/- 1.5 degrees) than that of area 17. Binocular interactions of cortical neurons were tested with the Risley biprism technique. Area 19 cells had maximal responses to binocular stimulation when the receptive-field disparities were either close to zero or slightly divergent. In contrast, area 17 cells tended to respond optimally to disparities that were either slightly or strongly convergent. At the level of the lateral geniculate nucleus there were significant differences between the receptive-field disparities inferred from the comparison of receptive-field positions of adjacent neurons recorded on either side of the border between the A and A1 geniculate laminae and those inferred from a similar comparison at the C1-C2 border. The mean horizontal disparities inferred from the interlaminar comparison at the A-A1 border were +2.1 degrees (+/- 0.3 degrees); those inferred from the interlaminar comparison at the C1-C2 border -0.2 (+/- 0.2 degrees) were more divergent.(ABSTRACT TRUNCATED AT 400 WORDS)     

急性毁损猫的初级视区使高级视区细胞失去对视觉刺激的诱发反应(英文)

心理物理学研究提示,初级视区毁损后的视觉残留可能是通过外纹状皮层的神经网络重组介导的,但缺少支持这一假说的电生理实验证据。采用在体细胞外单细胞记录技术,该研究分别检测了初级视区(主要包括17和18区)急性毁损猫和正常对照猫的高级视区(包括19、20和21区)神经元对不同视觉刺激的反应性。结果显示,与对照相比,急性毁损初级视区使99.3%的高级视区神经元丧失对运动光栅刺激的诱发反应,93%的神经元丧失对闪光刺激的反应。该结果表明,急性毁损成年猫的初级视皮层可能会导致其绝大部分视觉能力丧失。在幼年期实施初级视皮层毁损后,成年猫出现的残留视觉可能主要是由于手术后皮层下神经核团与外纹状皮层之间的通路重组引起的。     

Decoding the different states of visual attention using functional and effective connectivity features in fMRI data

The present paper concentrates on the impact of visual attention task on structure of the brain functional and effective connectivity networks using coherence and Granger causality methods. Since most studies used correlation method and resting-state functional connectivity, the task-based approach was selected for this experiment to boost our knowledge of spatial and feature-based attention. In the present study, the whole brain was divided into 82 sub-regions based on Brodmann areas. The coherence and Granger causality were applied to construct functional and effective connectivity matrices. These matrices were converted into graphs using a threshold, and the graph theory measures were calculated from it including degree and characteristic path length. Visual attention was found to reveal more information during the spatial-based task. The degree was higher while performing a spatial-based task, whereas characteristic path length was lower in the spatial-based task in both functional and effective connectivity. Primary and secondary visual cortex (17 and 18 Brodmann areas) were highly connected to parietal and prefrontal cortex while doing visual attention task. Whole brain connectivity was also calculated in both functional and effective connectivity. Our results reveal that Brodmann areas of 17, 18, 19, 46, 3 and 4 had a significant role proving that somatosensory, parietal and prefrontal regions along with visual cortex were highly connected to other parts of the cortex during the visual attention task. Characteristic path length results indicated an increase in functional connectivity and more functional integration in spatial-based attention compared with feature-based attention. The results of this work can provide useful information about the mechanism of visual attention at the network level.     

Distribution of neuropeptide Y immunoreactivity in human visual cortex and underlying white matter

Immunocytochemical techniques have been used to study neuropeptide Y (NPY) distribution in the human visual cortex (Brodman's areas 17, 18 and 19) NYP cell bodies belong mostly to inhibitory (multipolar and bitufted) but also to excitatory (bipolar and some pyramidal) neuronal types. Their distribution is similar in the three cortical areas studied: 20 to 40% of the NPY perikarya are located in the cortical gray matter, mostly in the deep layers, while the remaining 60 to 80% are located in the underlying white matter. Immunoreactive NPY processes form a rich network of intersecting fibers throughout the entire visual cortex. A superficial plexus (layers I and II) and a deep plexus (deep layer V and layer VI) of NPY fibers are present in areas 17, 18 and 19. In area 17, an additional well developed plexus is present in layers IVb and IVc. These plexuses receive branches from long parallel fibers arising from deep cortical layers or underlying white matter and terminating in superficial layers. Local or extrinsic NPY terminals wind around vessels in the cortex as well as in the white matter, and either penetrate them or form clusters of club endings on their walls. Our results suggest a role for NPY in human visual circuitry and in cortical blood flow regulation.     

In vitro selection of RNAs that undergo autolytic cleavage with Pb2+.

An in vitro selection method has been developed to obtain RNA molecules that specifically undergo autolytic cleavage reactions by Pb2+ ion. The method utilizes a circular RNA intermediate which is regenerated following the cleavage reaction to allow amplification and multiple cycles of selection. Pb2+ is known to catalyze a specific cleavage reaction between U17 and G18 of yeast tRNA(Phe). Starting from pools of RNA molecules which have a random distribution of sequences at nine or ten selected positions in the sequence of yeast tRNA(Phe), we have isolated many RNA molecules that undergo rapid and specific self-cleavage with Pb2+ at a variety of different sites. Terminal truncation experiments suggest that most of these self-cleaving RNA molecules do not fold like tRNA. However, two of the variants are cleaved rapidly with Pb2+ at U17 even though they lack the highly conserved nucleotides G18 and G19. Both specific mutations and terminal truncation experiments suggest that the D and T loops of these two variants interact in a manner similar to that of tRNA(Phe) despite the absence of the G18U55 and G19C56 tertiary interactions. A model for an alternate tertiary interaction involving a U17U55 pair is presented. This model may be relevant to the structure of about 100 mitochondrial tRNAs that also lack G18 and G19. The selection method presented here can be directly applied to isolate catalytic RNAs that undergo cleavage in the presence of other metal ions, modified nucleotides, or sequence-specific nucleases.     

Light and electron microscopic immunocytochemical analysis of the dopamine innervation of the rat visual cortex

Brain Cell Biology - The dopaminergic innervation of the rat primary (area 17) and secondary (areas 18 and 18a) visual cortical areas was examined immunocytochemically using an antiserum directed...     

Retinotopic organization of striate and extrastriate visual cortex in the golden hamster (Mesocricetus auratus).

The visual topography within striate and lateral extrastriate visual cortices was studied in adult hamsters. The cortical areas 17 and 18a in the left hemisphere were electrophysiologically mapped upon stimulation of the right eye, correlating receptive field positions in the visual field with cortical recording sites. Reference lesions were placed at selected cortical sites. Like in rats and other mammals, the lateral extrastriate cortex contained multiple representations of the visual field. Rostral area 18a contained the rostrolateral maps, with medial and lateral divisions. More caudally and sharing a common border with V1, maps in lateromedial, posterolateral and posterior areas were found. More laterally and forming a "third tier" of visual maps, anterolateral, laterolateral-anterior, laterolateral and laterolateral-posterior areas were found. There was also an indication of a possible pararhinal map. The plan so defined is virtually identical to that of rats. The results may be useful to understand a basic mammalian plan in the organization of the visual cortex.     

Organization of the cortico-ponto-cerebellar pathway to the dorsal paraflocculus. An experimental study with anterograde and retrograde transport of WGA-HRP in the cat.

To reveal the organization and relative magnitude of connections from various parts of the cerebral cortex to the dorsal paraflocculus via the pontine nuclei, WGA-HRP was injected in the dorsal paraflocculus in conjunction with injection of the same tracer in various parts of the cerebral cortex in 17 cats. Termination areas of cortical fibres (anterogradely labelled) and pontine neurons projecting to the dorsal paraflocculus (retrogradely labelled) were carefully plotted in serial transverse sections. As an average of countings in ten cats, 90% of the labelled cells were found in the pontine nuclei contralateral to the injection, and the majority (70%) were located in the rostral half of the nuclei. The highest degree of overlap between anterograde and retrograde labelling was found after injections of the parietal association cortex (areas 5 and 7). In an experiment with double anterograde tracing, it was shown that both area 5 and 7 contribute substantially to the cerebral inputs to the dorsal paraflocculus. High degree of overlap also occurred after injections of several visual cortical areas (areas 17, 18, 19, 20 and the posteromedial lateral suprasylvian visual area, PMLS). Cases with injections restricted to individual visual areas indicate that they all contribute to the parafloccular input. Considerably less overlap occurred after injections of the primary sensorimotor region (SI, MI) and second somatosensory area (SII), while the supplementary motor area, the auditory cortex and gyrus cinguli probably have no or very restricted access to the dorsal paraflocculus. It is concluded that the dorsal paraflocculus has its major cortical input from the parietal association cortex and the visual cortical areas. Since all the various cortical regions studied project to largely different parts of the pontine nuclei, and overlap with neurons projecting to the dorsal paraflocculus takes place at numerous places, it follows that the pontine neurons projecting to the dorsal paraflocculus must consist of many subgroups differing with regard to their cortical input.     

The organization of corticocortical projections from area 17 to area 18 of the cat's visual cortex

Retrogradely transported tracers were injected into area 18 of the visual cortex of the adult cat to study the organization of corticocortical projections from area 17 to area 18. All injections, whether very small or relatively large, and irrespective of their exact location in area 18, produced a discontinuous, clustered distribution of labelled cells, mainly in layers II, III and upper IV, in a topographically related region of area 17. The mean centre-centre distance between neighbouring patches was about 750 microns. We conclude that the overall population of cells projecting to area 18 is genuinely distributed in a patchy fashion and that they provide an efficient spatial sample of information from area 17. Comparison of the dimensions of each injection site and of the retrogradely labelled territory suggested that each region in area 18 receives a convergent input from a zone in area 17 whose visual field representation is about 0.8 M-1 deg larger in all directions (where M is the magnification factor in millimetres per degree at the termination site in area 18). Pairs of injection were made in area 18 by placing small volumes of two fluorescent tracers, fast blue and diamidino yellow, side-by-side in either a rostrocaudal or a mediolateral plane, with different distances between them. When the boundaries of the dense central cores of two injection sites were separated, at their closest points, by about 1.6 mm, the two corresponding distributions of labelled cells in area 17 were just non-overlapping, suggesting that each group of cells in area 17 sends a divergent projection in innervate a zone about 0.8 mm larger in all directions in area 18. More closely spaced injections led to overlap of the distributions of labelling by the two dyes, with shared clusters containing a mixture of labelled cells. The proportion of double-labelled cells in these shared clusters never exceeded 4.4% (but was 70% after sequential injection of the two dyes at a single point). We conclude that, although each cluster of cells sends a divergent projection to area 18, the majority of individual axons terminate more discretely, perhaps providing specific inter-connections between functionally corresponding 'columns' in the two areas.     

The influence of strabismus and monocular deprivation on the size of callosal cells in cortical areas 17 and 18 of the cat

To reveal the changes in visual cortex structure following impaired early binocular experience, the size (somatic area) of callosal cells in areas 17, 18 ofmonocularly deprived and convergent strabismic cats was measured. Horseradish peroxidase was injected into the single ocular dominance columns of areas 17, 18 and the transition zone 17/18. In both groups of impaired cats the mean size of callosal cells in area 17 was increased in comparison to intact cats. In area 18, the similar difference was found in monocularly deprived cats only. It was shown that the differences in the mean sizes of cells are due to the increase of the number of large cells. In strabismic cats, the portion of large cells (soma > 200 mkm2) in area 17 was 58% and in area 18 was 8%. The relative share of large cells in areas 17 and 18 of monocularly deprived cats was similar (28 and 26 % correspondingly). These data show that early binocular vision impairments may lead to the changes in cytoarchitecture of cortical layers where the interhemispheric connections originate.     

Responses to lightness variations in early human visual cortex

Lightness is the apparent reflectance of a surface, and it depends not only on the actual luminance of the surface but also on the context in which the surface is viewed [1-10]. The cortical mechanisms of lightness processing are largely unknown, and the role of early cortical areas is still a matter of debate [11-17]. We studied the cortical responses to lightness variations in early stages of the human visual system with functional magnetic resonance imaging (fMRI) while observers were performing a demanding fixation task. The set of dynamically presented visual stimuli included the rectangular version of the classic Craik-O'Brien stimulus [3, 18, 19] and a variant that led to a weaker lightness effect, as well as a pattern with actual luminance variations. We found that the cortical activity in retinotopic areas, including the primary visual cortex (V1), is correlated with context-dependent lightness variations.     

On the modeling of the performances of the human brain in a two-choice task involving decoding and memorization of simple visual patterns

The quantitative, aspects of the decoding and storage processes of simple visual patterns by the human brain are considered, on the basis of the performances obtained in a set of two-choice experiments. Strings of patterns (colored lights or simple geometrical patterns) were used in which the densities of the two patterns throughout the string were either constant or asymmetric. The subjects were required to indicate the pattern which was presented more frequently. A nonlinear model for the storage and decision processes was devised from these data which accurately predicted the performance under experimental conditions different from those originally used. Among the prominent features of the brain processes suggested by the model are the necessity for a nonlinear summation of the decoded information and its decay with time.Finally, it is shown that the experimental design allows a quantitative evaluation of those factors which are relevant to the decoding of patterns of different complexities.     

The relationship between patterns of DNA replication and of Quinacrine fluorescence in the human chromosome complement

Cultured human peripheral blood lymphocytes were labelled with ³H-thymidine in the early or late S phase prior to mitosis. Quinacrine fluorescence patterns in metaphase chromosomes were then recorded photographically and the slides reprocessed for autoradiography so that the same metaphase cells were examined with the two techniques. The intensity and distribution of ³H-thymidine labelling was compared with the intensity and distribution of Q fluorescence with particular reference to chromosomes 1, 13, 14, 15, 17, 18, 19, 20, 21 and 22. It was found that chromosome regions showing bright fluorescence were also late replicating and that, in general, patterns of late replications reflected the patterns of fluorescence. Exceptions to this generalisation included the late labelling X chromosome in cells of female origin and areas near the centromeres on chromosomes 1, 9, 16 and 22. These centromeric regions show a dull fluorescence but, with exception of chromosome 9, are strongly Giemsa-positive in the ASG staining technique. On the basis of staining reaction, late replicating heterochromatic regions fall into five categories, the relationships and functional significance of these categories is discussed.