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.     

Reorganization of callosal interhemispheric connections in the adult cat: effects of monocular occlusion after chiasmotomy

Two groups of adult cats were chiasmotomized and their cortical receptive fields (17-18 boundary) were compared after a postoperative period of ca 6 weeks. In one group, binocular vision was maintained during that period, in the other one, one eye was sutured at the time of the chiasmotomy, depriving one hemisphere from patterned vision through the direct pathway. In monocular chiasmotomized animals, the receptive fields to stimulation of the contralateral eye were significantly larger than in the binocular ones.     

Responses of simple and non-oriented cells to stimuli of variable duration in areas 17 and 18 of cat visual cortex.

Single unitresponses to photic stimuli of variable duration were studied in the cat visual areas 17 and 18. The closed-chamber technique was used to record extracellularly impulsive electrical activity in locally anaesthetized, Flaxedil-paralyzed and artificially ventilated cats. Stimulus duration ranges between 0.020 and 10 sec, the background luminance and the intensity of stimuli being constant. We found a first group of cells which fire independently of the stimulus duration; a second group which fire in close relation to the stimulus duration in a rather wide range of values, and a third group which fire monotonously as long as the stimulus goes on. The three groups of cells are supposed to be three functionally different types of cortical cells.     

Organization of somatic nerve projections in various cortical areas of the cat cerebellum

We conducted a layer analysis of evoked potentials arising in various cortical cerebellar areas (vermis and intermediate zones of the anterior lobe, and the ansiform lobe) of non-anesthetized cats upon stimulation of nerves in fore- and hindlimbs. This analysis yielded the conclusion on the arrival of stimuli at the cerebellar cortex over two types of moss fibers innervating two types of granule cells which we described earlier. Impulses transmitted over type I moss fibers stimulate Purkinje cells. The activation of type II moss fibers has no immediate effect on these cells. Type I moss fibers terminate in the vermis and the intermediate zone of the hemispheres and do not terminate in the lateral hemispheric region. While projections of type I moss fibers are somatotopically organized in the intermediate zone they are diffuse in the vermis. Type II moss fibers terminate in all the regions of the crebellar cortex under study, but their projections show no somatotopic organization. The question of the afferent pathways terminating as type I and II moss fibers is discussed.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 166–174, March–April, 1971.     

The responses to illusory contours of neurons in cortex areas 17 and 18 of the cats

Responses to illusory contours (ICs) were sampled from neurons in cortical areas 17 and 18 of the anesthetized cats. For ICs sensitive cells, the differences of receptive field properties were compared when ICs and real contour stimuli were applied. Two hundred orientation or direction selective cells were studied. We find that about 42 percent of these cells were the ICs sensitive cells. Although their orientation or direction tuning curves to ICs bar and real bars were similar, the response modes (especially latency and time course) were different. The cells' responses to ICs were independent of the spatial phases of sinusoidal gratings, which composed the ICs. The cells' optimal spatial frequency to composing gratings the ICs was much higher than the one to moving gratings. Therefore, these cells really responded to the ICs rather than the line ends of composing gratings. For some kinds of velocity-tuning cells, the optimal velocity to moving ICs bar was much lower than the optimal velocity to moving     

The responses to illusory contours of neurons in cortex areas 17 and 18 of the cats

Responses to illusory contours (ICs) were sampled from neurons in cortical areas 17 and 18 of the anesthetized cats. For ICs sensitive cells, the differences of receptive field properties were compared when ICs and real contour stimuli were applied. Two hundred orientation or direction selective cells were studied. We find that about 42 percent of these cells were the ICs sensitive cells. Although their orientation or direction tuning curves to ICs bar and real bars were similar, the response modes (especially latency and time course) were different. The cells’ responses to ICs were independent of the spatial phases of sinusoidal gratings, which composed the ICs. The cells’ optimal spatial frequency to composing gratings the ICs was much higher than the one to moving gratings. Therefore, these cells really responded to the ICs rather than the line ends of composing gratings. For some kinds of velocity-tuning cells, the optimal velocity to moving ICs bar was much lower than the optimal velocity to moving bars. The present results demonstrate that some cells in areas 17 and 18 of cats have the ability to respond to ICs and have different response properties of the receptive fields to ICs and luminance boundaries via different neural mechanisms.     

Activity of callosal neurons of the visual cortex in the cat

Activity of 28 identified neurones of the visual cortex was recorded in cats immobilized by d-tubocurarine. Stimulation of the callosal body with a single stimulus or high-frequency train elicited a short-latency antidromic reaction of neurones in the visual cortex whose axons constitute the main part of the large cerebral commissure. Some commissural neurones responded to a single callosal stimulation by two action potentials the first one being antidromic, the second one being of long-latency postsynaptic origin. The second action potential was generated as a result of activation of axonal collaterals of the same neurone or the neighboring callosal neurones. More than a half of callosal neurones responded to a single stimulation of the lateral geniculate body by short-latency antidromic discharges and by long-latency postsynaptic reactions. These data indicate the existence of the systems of two-way neuronal connections, i.e. calloso-geniculate and geniculo-callosal ones.     

Anatomical connectivity defines the organization of clusters of cortical areas in the macaque monkey and the cat

The number of different cortical structures in mammalian brains and the number of extrinsic fibres linking these regions are both large. As with any complex system, systematic analysis is required to draw reliable conclusions about the organization of the complex neural networks comprising these numerous elements. One aspect of organization that has long been suspected is that cortical networks are organized into 'streams' or 'systems'. Here we report computational analyses capable of showing whether clusters of strongly interconnected areas are aspects of the global organization of cortical systems in macaque and cat. We used two different approaches to analyse compilations of corticocortical connection data from the macaque and the cat. The first approach, optimal set analysis, employed an explicit definition of a neural 'system' or 'stream', which was based on differential connectivity. We defined a two-component cost function that described the cost of the global cluster arrangement of areas in terms of the areas' connectivity within and between candidate clusters. Optimal cluster arrangements of cortical areas were then selected computationally from the very many possible arrangements, using an evolutionary optimization algorithm. The second approach, non-parametric cluster analysis (NPCA), grouped cortical areas on the basis of their proximity in multidimensional scaling representations. We used non-metric multidimensional scaling to represent the cortical connectivity structures metrically in two and five dimensions. NPCA then analysed these representations to determine the nature of the clusters for a wide range of different cluster shape parameters. The results from both approaches largely agreed. They showed that macaque and cat cortices are organized into densely intra-connected clusters of areas, and identified the constituent members of the clusters. These clusters reflected functionally specialized sets of cortical areas, suggesting that structure and function are closely linked at this gross, systems level.     

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.