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1.

001-es BibID:BIBFORM033341
Első szerző:Buzás Péter
Cím:Independence of visuotopic representation and orientation map in the visual cortex of the cat / Péter Buzás, Maxim Volgushev, Ulf T. Eysel, Zoltán F. Kisvárday
Dátum:2003
ISSN:0953-816X
Megjegyzések:The representations of visual space and stimulus orientation were mapped in the cat primary visual cortex using electrophysiological recordings supplemented with intrinsic signal optical imaging. The majority of units displaced up to 600 micro m laterally had overlapping RFs both in orientation domains and around singularities of the orientation map. Quantitative comparison of these units revealed only a weak, positive correlation between the difference in their preferred orientations and RF separations (area 17: r = 0.09; area 18: r = 0.15). The occurrence of nonoverlapping RFs could be accounted for by random RF position scatter rather than by orientation difference between the units. Monte Carlo analysis showed that our findings are compatible with a locally smooth and linear representation of visual space that is not coupled to the representation of stimulus orientation. An important functional implication of the above map relationships is that positional information captured by the retina is faithfully transmitted into the cortex.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:The European Journal of Neuroscience. - 18 : 4 (2003), p. 957-968. -
További szerzők:Volgushev, Maxim Eysel, Ulf T. Kisvárday Zoltán (1957-) (biológus, neurobiológus)
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2.

001-es BibID:BIBFORM033354
Első szerző:Crook, John M.
Cím:Evidence for a contribution of lateral inhibition to orientation tuning and direction selectivity in cat visual cortex : reversible inactivation of functionally characterized sites combined with neuroanatomical tracing techniques / John M. Crook, Zoltan F. Kisvárday, Ulf T. Eysel
Dátum:1998
ISSN:0953-816X
Megjegyzések:We have previously reported that cells in cat areas 17 and 18 can show increases in response to non-optimal orientations or directions, commensurate with a loss of inhibition, during inactivation of laterally remote, visuotopically corresponding sites by iontophoresis of gamma-aminobutyric acid (GABA). We now present anatomical evidence for inhibitory projections from inactivation sites to recording sites where 'disinhibitory' effects were elicited. We made microinjections of [3H]-nipecotic acid, which selectively exploits the GABA re-uptake mechanism, < 100 microm from recording sites where cells had shown either an increase in response to non-optimal orientations during inactivation of a cross-orientation site (n = 2) or an increase in response to the non-preferred direction during inactivation of an iso-orientation site with opposite direction preference (n = 5). Retrogradely labelled GABAergic neurons were detected autoradiographically and their distribution was reconstructed from series of horizontal sections. In every case, radiolabelled cells were found in the vicinity of the inactivation site (three to six within 150 microm). The injection and inactivation sites were located in layers II/III-IV and their horizontal separation ranged from 400 to 560 microm. In another experiment, iontophoresis of biocytin at an inactivation site in layer III labelled two large basket cells with terminals in close proximity to cross-orientation recording sites in layers II/III where disinhibitory effects on orientation tuning had been elicited. We argue that the inactivation of inhibitory projections from inactivation to recording sites made a major contribution to the observed effects by reducing the strength of inhibition during non-optimal stimulation in recurrently connected excitatory neurons presynaptic to a recorded cell. The results provide further evidence that cortical orientation tuning and direction selectivity are sharpened, respectively, by cross-orientation inhibition and iso-orientation inhibition between cells with opposite direction preferences.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:The European Journal of Neuroscience. - 10 : 6 (1998), p. 2056-2075. -
További szerzők:Kisvárday Zoltán (1957-) (biológus, neurobiológus) Eysel, Ulf T.
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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3.

001-es BibID:BIBFORM033406
035-os BibID:WOS:A1994PP97600012 PMID:7850026
Első szerző:Kisvárday Zoltán (biológus, neurobiológus)
Cím:Relationship between lateral inhibitory connections and the topography of the orientation map in cat visual cortex / Zoltán F. Kisvárday, Dae-Shik Kim, Ulf T. Eysel, Tobias Bonhoeffer
Dátum:1994
ISSN:0953-816X
Megjegyzések:The functional and structural topography of lateral inhibitory connections was investigated in visual cortical area 18 using a combination of optical imaging and anatomical tracing techniques in the same tissue. Orientation maps were obtained by recording intrinsic signals in regions of 8.4-19 mm(2). To reveal the inhibitory connections provided by large basket cells, biocytin was iontophoretically injected at identified orientation sites guided by the pattern of surface blood vessels. The axonal and dendritic fields of two retrogradely labelled large basket cells were reconstructed in layer III. Their axonal fields extended up to 1360 mu m from the parent somata. In addition to single basket cells, the population of labelled basket cell axons was also studied. For this analysis anterogradely labelled basket axons running horizontally over 460-1280 mu m from the core of an injection site in layer III were taken into account. The distribution of large basket cell terminals according to orientation preferences of their target regions was quantitatively assessed. Using the same spatial resolution as the orientation map, a frequency distribution of basket cell terminals dependent on orientation specificity could be derived. For individual basket cells, the results showed that, on average, 43% of the terminals provided input to sites showing similar orientation preferences (+/-30 degrees) to those of the parent somata. About 35% of the terminals were directed to sites representing oblique-orientation [+/-(30-60)degrees], and 22% of them terminated at cross-orientation sites [+/-(60-90)degrees]. Furthermore, the possible impact of large basket cells on target cells at different distances and orientation preferences was estimated by comparing the occurrence of orientation preferences with the occurrence of basket terminals on the distance scale. It was found that a basket cell could elicit iso-orientation inhibition with a high impact between 100-400 and 800-1200 mu m, strong cross-orientation inhibition at similar to 400-800 mu m, and oblique-orientation inhibition between 300-500 and 700-900 mu m from the parent soma. The non-isotropic topography of large basket axons suggests a complex function for this cell class, possibly including inhibition related to orientation and direction selectivity depending on the location of the target cells and possible target selectivity.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:European Journal Of Neuroscience. - 6 : 10 (1994), p. 1619-1632. -
További szerzők:Kim, Dae-Shik Eysel, Ulf T. Bonhoeffer, Tobias
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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4.

001-es BibID:BIBFORM033404
035-os BibID:WOS:A1993MN58800002 PMID:8124514
Első szerző:Kisvárday Zoltán (biológus, neurobiológus)
Cím:Functional and structural topography of horizontal inhibitory connections in cat visual cortex / Zoltán F. Kisvárday, Ulf T. Eysel
Dátum:1993
ISSN:0953-816X
Megjegyzések:The functional organization of long-horizontal inhibitory connections was studied in cat visual cortical area 17, using a combination of electrophysiological recording and anatomical tracing in the same tissue. Orientation maps were obtained by recording multiunit activity from layer III at regular intervals (100-300 mum) in a region of approximately 1.3 mm2 of cortex at a depth corresponding to the location of the basket cell axons reconstructed later. Before the physiological mapping, the neuronal tracer biocytin had been iontophoretically injected at one functionally characterized site. On the basis of light microscopic features a total of five biocytin-labelled large basket axons, BC1 - BC5, were reconstructed from series of horizontal sections of two cats. The parent somata and dendritic fields of three axons (BC1, BC4 and BC5) could also be reconstructed. The axonal field of basket cell BC1 had an overall lateral spread of 1.8 mm. The axons of basket cells BC4 and BC5 spanned a distance of 3.05 and 2.85 mm, respectively. The distribution pattern of histologically reconstructed recording sites and of five labelled basket cell axons were directly compared in the same sections. The results show that a single large basket cell provides input to regions representing the whole range of orientations, i.e. iso-orientation (+/-30-degrees), oblique orientation (+/-[30-60]-degrees) and cross-orientation (+/-[60-90]-degrees) to that at the basket cell's soma. Furthermore, the differential effect mediated by the same large basket cell at sites of different orientation preference was numerically estimated for two basket cells (BC4 and BC5) whose preferred orientations could be determined on the basis of recording sites adjacent to their parent somata. We counted the number of axonal terminals of these basket cells at iso-, oblique- and cross-orientation sites and found no significant difference in the average density of terminals at sites of either orientation preference. The functional topography of large basket cell axons indicates that the same basket cell can mediate iso-, oblique- and cross-orientation inhibition at different sites. Hence, we assume that large basket cells serve a complex physiological role depending on the location of target cells in the orientation map.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:European Journal Of Neuroscience. - 5 (1993), p. 1558-1572. -
További szerzők:Eysel, Ulf T.
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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5.

001-es BibID:BIBFORM033353
Első szerző:Yousef, Tagrid
Cím:Orientation topography of layer 4 lateral networks revealed by optical imaging in cat visual cortex (area 18) / Tagrid Yousef, Tobias Bonhoeffer, Dae-Shik Kim, Ulf T. Eysel, Éva Tóth, Zoltán F. Kisvárday
Dátum:1999
ISSN:0953-816X
Megjegyzések:The functional specificity of corticocortical connections with respect to the topography of orientation selectivity was studied by optical imaging of intrinsic signals and bulk injections of fluorescent latex beads (green and red) and biocytin into layer 4. The distributions of retrogradely labelled cells and anterogradely labelled axon terminals were histologically reconstructed from all cortical laminae, and the resulting anatomical maps compared with the optically imaged functional maps. Layer 4 injections produced extensive horizontal labelling up to 2-3 mm from the injection centres albeit without the clear patchy pattern described after layer 2/3 injections (Gilbert & Wiesel 1989, J. Neurosci., 9, 2432-2442; Kisvárday et al. 1997, Cerebral Cortex, 7, 605-618). The functional (orientation) distribution of the labelled projections was analysed according to laminar location and lateral spread. With regard to the former, no major difference in the orientation topography between supragranular- (upper tier), granular- (middle tier) and infragranular (lower tier) layers was seen. Laterally, proximal and distal projections were distinguished and further dissected into three orientation categories, iso- (+/- 30 degrees ), oblique- (+/- 30-60 degrees ) and cross-orientations (+/- 60-90 degrees ) with respect to the orientation preference at the injection sites. The majority of distal connections (retrograde and anterograde) was equally distributed across orientations (35.4% iso-, 33.7% oblique-, and 30.9% cross-orientations) that are equivalent with a preponderance to dissimilar orientations (oblique- and cross-orientations, 64.6%). In one case, distal excitatory and inhibitory connections could be morphologically distinguished. For both categories, a marked bias to dissimilar orientations was found (excitatory, 63.7%; inhibitory, 86.6%). Taken together, these results suggest that the long-range layer 4 circuitry has a different functional role from that of the iso-orientation biased (52.9%, Kisvárday et al. 1997, Cerebral Cortex, 7, 605-618) layer 2/3 circuitry, and is perhaps involved in feature difference-based mechanisms, e.g. figure ground segregation.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:The European Journal of Neuroscience. - 11 : 12 (1999), p. 4291-4308. -
További szerzők:Bonhoeffer, Tobias Kim, Dae-Shik Eysel, Ulf T. Tóth Éva Kisvárday Zoltán (1957-) (biológus, neurobiológus)
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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