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R Gattass

Publications and source records attributed to R Gattass.

At least 37 records · Page 2Linked to original sources
PubMed1992

Laminar, columnar and topographic aspects of ocular dominance in the primary visual cortex of Cebus monkeys.

The representation of the two eyes in striate cortex (V1) of Cebus monkeys was studied by electrophysiological single-unit recordings in normal animals and by morphometric analysis of the pattern of ocular dominance (OD) stripes, as revealed by cytochrome oxidase histochemistry in V1 flat-mounts of enucleated animals. Single-unit recordings revealed that the large majority of V1 neurons respond to the stimulation of either eye but are more strongly activated by one of them. As in other species of monkey, neurons with preference for the stimulation of the same eye are grouped in columns 300-400 microns wide, spanning all cortical layers. Monocular neurons are clustered in layer IVc, specially in its deeper half (IVc-beta), and constitute less than 10% of the population of other layers. Neurons with equal responses to each eye are more commonly found in layer V than elsewhere in V1. In the supragranular layers and in granular layer IVc-alpha neurons strongly dominated by one of the eyes tend to be broadly tuned for orientation, while binocularly balanced neurons tend to be sharply tuned for this parameter. No such correlation was detected in the infragranular layers, and most neurons in layer IVc-beta responded regardless of stimulus orientation. Ocular dominance stripes are present throughout most of V1 as long, parallel or bifurcating bands alternately dominated by the ipsi- or the contralateral eye. They are absent from the cortical representations of the blind spot and the monocular crescent. The domains of each eye occupy nearly equal portions of the surface of binocular V1, except for the representation of the periphery, where the contralateral eye has a larger domain, and a narrow strip along the border of V1 with V2, where either eye may predominate. The orderliness of the pattern of stripes and the relationship between stripe arrangement and the representation of the visual meridians vary with eccentricity and polar angle but follow the same rules in different animals. These results demonstrate that the laminar, columnar and topographic distribution of neurons with different degrees of OD in V1 is qualitatively similar in New- and Old World monkeys of similar sizes and suggest that common ancestry, rather than parallel evolution, may account for the OD phenotypes of contemporaneous simians.

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PubMed1991

Topographic organization of cortical input to striate cortex in the Cebus monkey: a fluorescent tracer study.

Cortical afferents to area V1 were studied in seven Cebus monkeys by means of retrograde fluorescent tracers. Injections were placed in V1, under electrophysiological guidance, in the regions of representation of both the upper and lower visual quadrants, at eccentricities that ranged from 0.5 to 64 degrees. In all cases retrogradely filled neurons were found in retinotopically corresponding portions of areas V2 and MT, as defined electrophysiologically (Rosa et al: J. Comp. Neurol. 275:326, 1988; Fiorani et al: J Comp Neurol 287:98, 1989). The results also revealed two other visual zones located anterior to V2 here named third and fourth visual areas. A topographical organization of the connections was observed in these areas, with upper quadrant located ventrally and lower quadrant located dorsally. A clear central-peripheral gradient, from the lateral to the medial cortical surface, was also observed in these areas. Lower field injections revealed crude topographic organization in area DZ and a diffuse projecting zone in the annectent gyrus. Peripheral injections in V1 revealed a clear upper and lower field segregation in areas PO and prostriata as well as a complex topography in MST. In addition, another region of labeling revealed the presence of an area, the temporal ventral posterior region, with an organized topographic representation of the upper field, with a central to peripheral gradient, from the lateral to the medial cortical surface. Three groups of cortical areas were distinguished according to the laminar distribution of neurons labeled from V1. In the first group, which is characterized by dense infra- and supragranular labeling, only V2 was included. The second group consists of areas V3, MT, and PO. These areas show dense labeling in the infragranular layers and occasionally sparse labeling in the supragranular layers. Finally, V4 and the other projecting areas, which are characterized by exclusive labeling of the infragranular layers were included in the third group.

Afferent Pathways↗
PubMed1991

A quantitative analysis of cytochrome oxidase-rich patches in the primary visual cortex of Cebus monkeys: topographic distribution and effects of late monocular enucleation.

We have studied the tangential distribution of cytochrome oxidase (cytox)-rich patches in striate cortex of normal and monocularly enucleated Cebus apella monkeys. Patch spatial density and patch cross-sectional area were analysed in cytox-reacted tangential sections of flat-mounted preparations of V1. In the upper cortical layers of V1, and specially in the middle of layer III, the Cebus has well-delimited cytox-rich patches. Rows of patches are less conspicuous in Cebus than in Old World monkeys. The spatial density of patches is nearly constant throughout the binocular field representation in V1, with a mean value of 4 patches per mm2. In the monocular portions of V1, however, patch spatial density diminishes. In most cases, mean patch cross-sectional area decreases slightly towards the representation of the periphery in V1. However, patches in the representation of the monocular crescent tend to be larger than those in the adjacent binocular representation. The small variation of cytox patch topography with eccentricity contrasts with the large variation of cortical point-image size in V1. In monocularly enucleated monkeys, patches are larger and darker above and below the ocular dominance stripes of the remaining eye than in the alternate stripes. After long-term enucleation, the patches corresponding to the remaining eye columns appeared larger than in normal controls. In contrast, there is no difference in size between the patches located in the deprived and undeprived monocular crescent representations, although both patch and interpatch regions are darker staining in the latter. These results suggest the existence of competitive interactions which modify the cortical intrinsic organization even in adult monkeys.

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PubMed1990

Cortical streams of visual information processing in primates.

1. The topographic organization of the cortical visual areas in the Cebus monkey and their anatomical connections support the subdivision of the visual pathways into ventral and dorsal streams of visual information processing. 2. We propose that the dorsal stream, as defined by Ungerleider and Mishkin (In: Ingle DJ, Goodale MA and Mansfield RJW (Editors), Analysis of Visual Behavior. MIT Press, Boston, 1982), be subdivided into dorsolateral and dorsomedial streams, which are concerned with different aspects of the processing of motion and spatial perception. 3. The data support the hypothesis of concurrent, modular processing of visual attributes in cortical visual areas in the different streams, and highlight some features of the visual field representation in each area which may reflect functional specialization of these streams. 4. The visual topography is locally disrupted in some cortical areas by the existence of functionally different modules. However, a global visuotopic organization is preserved in most areas. 5. The visuotopic organization may provide the address of space coordinates to integrate information concerning the same retinotopic locus across different visual areas.

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PubMed1989

Visual area MT in the Cebus monkey: location, visuotopic organization, and variability.

The representation of the visual field in the dorsal portion of the superior temporal sulcus (ST) was studied by multiunit recordings in eight Cebus apella, anesthetized with N2O and immobilized with pancuronium bromide, in repeated recording sessions. On the basis of visuotopic organization, myeloarchitecture, and receptive field size, area MT was distinguished from its neighboring areas. MT is an oval area of about 70 mm2 located mainly in the posterior bank of the superior temporal sulcus. It contains a visuotopically organized representation of at least the binocular visual field. The representation of the vertical meridian forms the dorsolateral, lateral, and ventrolateral borders of MT and that of the horizontal meridian runs across the posterior bank of ST. The fovea is represented at the lateralmost portion of MT, while the retinal periphery is represented medially. The representation of the central visual field is magnified relative to that of the periphery in MT. The cortical magnification factor in MT decreases with increasing eccentricity following a negative power function. Receptive field size increases with increasing eccentricity. A method to evaluate the scatter of receptive field position in multiunit recordings based on the inverse of the magnification factor is described. In MT, multiunit receptive field scatter increases with increasing eccentricity. As shown by the Heidenhain-Woelcke method, MT is coextensive with two myeloarchitectonically distinct zones: one heavily myelinated, located in the posterior bank of ST, and another, less myelinated, located at the junction of the posterior bank with the anterior bank of ST. At least three additional visual zones surround MT: DZ, MST, and FST. The areas of the dorsal portion of the superior temporal sulcus in the diurnal New World monkey Cebus are comparable to those described for the diurnal Old World monkey, Macaca. This observation suggests that these areas are ancestral characters of the simian lineage and that the differences observed in the owl monkey may be secondary adaptations to a nocturnal ecological niche.

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PubMed1988

Representation of the visual field in the second visual area in the Cebus monkey.

The representation of the visual field in the second visual area (V2) was reconstructed from multiunit visual responses and anatomical tracers. Receptive field plotting was performed during multiple recording sessions in seven Cebus apella monkeys under N2O/O2 and immobilized with pancuronium bromide. V2 forms a continuous belt of variable width around striate cortex (V1) except at the most anterior portion of the calcarine sulcus. In each hemisphere V2 contains a visuotopic representation of the contralateral visual hemifield. The representation of the vertical meridian is adjacent to that of V1 and forms the posterior border of V2. The representation of the fovea of V2 is adjacent to that of V1. The representation of the horizontal meridian (HM) is continuous with that of V1; then it splits to form the anterior border of V2, both dorsally and ventrally. The lower quadrant of the visual field is represented dorsally and the upper quadrant ventrally. The visual topography of V2 is coarser than that of V1. In V2, receptive fields corresponding to recording sites separated by a cortical distance of up to 4 mm may represent the same portion of the visual field. In three additional animals, combined injections of fluorescent tracers along the HM representation in V1 yielded two projection sites at the anterior border of V2. The split of the HM representation is estimated to occur at an eccentricity below 1 degree. Quantitative analysis showed that in V2 the representation of the central visual field is magnified relative to that of the periphery. The cortical magnification factor is greater along the isopolar dimension than along the isoeccentric one. Receptive field size in V2 increases with increasing eccentricity. In sections stained for myelin by the Heidenhein-Wöelcke method V2 can be distinguished from the surrounding cortex for most of its extent.

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PubMed1988

Topographical organization of cortical afferents to extrastriate visual area PO in the macaque: a dual tracer study.

We have examined the origin and topography of cortical projections to area PO, an extrastriate visual area located in the parieto-occipital sulcus of the macaque. Distinguishable retrograde fluorescent tracers were injected into area PO at separate retinotopic loci identified by single-neuron recording. The results indicate that area PO receives retinotopically organized inputs from visual areas V1, V2, V3, V4, and MT. In each of these areas the projection to PO arises from the representation of the periphery of the visual field. This finding is consistent with neurophysiological data indicating that the representation of the periphery is emphasized in PO. Additional projections arise from area MST, the frontal eye fields, and several divisions of parietal cortex, including four zones within the intraparietal sulcus and a region on the medial dorsal surface of the hemisphere (MDP). On the basis of the laminar distribution of labeled cells we conclude that area PO receives an ascending input from V1, V2, and V3 and receives descending or lateral inputs from all other areas. Thus, area PO is at approximately the same level in the hierarchy of visual areas as areas V4 and MT. Area PO is connected both directly and indirectly, via MT and MST, to parietal cortex. Within parietal cortex, area PO is linked to particular regions of the intraparietal sulcus including VIP and LIP and two newly recognized zones termed here MIP and PIP. The wealth of connections with parietal cortex suggests that area PO provides a relatively direct route over which information concerning the visual field periphery can be transmitted from striate and prestriate cortex to parietal cortex. In contrast, area PO has few links with areas projecting to inferior temporal cortex. The pattern of connections revealed in this study is consistent with the view that area PO is primarily involved in visuospatial functioning.

Animals↗
PubMed1988

Complete pattern of ocular dominance stripes in V1 of a New World monkey, Cebus apella.

The presence of ocular dominance (OD) stripes in layer IVc of striate cortex (V1) is characteristic of all Old World simians so far studied. In contrast, some species of New World monkeys do not have ocular dominance stripes, and in those that do, the pattern of stripes may be different from that shown in Old World monkeys. This difference has led to the suggestion that OD stripes evolved independently in both groups. We have mapped the entire system of OD stripes in the New World monkey Cebus, by means of cytochrome oxidase histochemistry after monocular enucleation. A striking similarity was found between the patterns in Cebus and Macaca, which is suggestive of common ancestry, rather than parallel evolution.

Animals↗
PubMed1988

Visuotopic organization and extent of V3 and V4 of the macaque.

The representation of the visual field in areas V3 and V4 of the macaque was mapped with multiunit electrodes. Twelve Macaca fascicularis were studied in repeated recording sessions while immobilized and anesthetized. V3 is a narrow strip (4-5 mm wide) of myeloarchitectonically distinct cortex located immediately anterior to V2. It contains a systematic representation of the central 35-40 degrees of the contralateral visual field; the representation of the upper quadrant is located ventrally in the hemisphere and that of the lower quadrant, dorsally. There is a small gap between the dorsal (V3d) and ventral (V3v) portions of V3. The representation of the horizontal meridian is adjacent to that in V2 and forms the posterior border of both V3d and V3v. Most or all of the anterior border of V3d consists of the representation of the lower vertical meridian. The entire anterior border of V3v consists of the representation of the upper vertical meridian. V4 is a strip of myeloarchitectonically distinct cortex 5-8 mm wide, immediately anterior to V3. It contains a coarse, but systematic, representation of approximately the central 35-40 degrees of the contralateral visual field. The representation of the upper visual field is located ventrally in the hemisphere. Most of the representation of the lower visual field is located dorsally. The posterior border of V4 corresponds to the representation of the vertical meridian, and the representation of the horizontal meridian is located at or near its anterior border. In both V3 and V4, the representation of the central visual field is magnified relative to that of the periphery. In both areas, the size of receptive fields increases with increasing eccentricity; however, at a given eccentricity, the receptive fields of V4 are larger than those of V3.

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PubMed1987

Visual topography of V1 in the Cebus monkey.

The representation of the visual field in the striate cortex (V1) was mapped with multiunit electrodes in the Cebus monkey. Nine Cebus apella, anesthetized with N2O and immobilized with pancuromium bromide were studied in repeated recording sessions. In each hemisphere, V1 contains a continuous representation of the contralateral visual hemifield. The representation of the vertical meridian (VM) forms the external border of V1 except at the anteriormost portion of the calcarine fissure. The representation of the horizontal meridian (HM) divides the area so that the representation of the lower visual field is located dorsally, and that of the upper field ventrally. The convoluted surface of V1 can be only partially unfolded, and no precise "flattened" map can be obtained without introducing surface discontinuities. The visual topography of V1 is presented in a series of coronal sections and in "flattened" maps. The representation of the central visual field is magnified relative to that of the periphery in V1. The evaluation of the cortical magnification factors measured along isoeccentric and isopolar dimensions in the partially unfolded model of V1 revealed anisotropies in the representation of the visual field with larger magnification along isopolar lines than along isoeccentric lines. Receptive field size increases with increasing eccentricity, whereas point image size decreases with increasing eccentricity.

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PubMed1981

Visual topography of V2 in the macaque.

The representation of the visual field in the area adjacent to striate cortex was mapped with multiunit electrodes in the macaque. The animals were immobilized and anesthetized and in each animal 30 to 40 electrode penetrations were typically made over several recording sessions. This area, V2, contains a topographically organized representation of the contralateral visual field up to an eccentricity of at least 80 degrees. The representation of the vertical meridian is adjacent to that in striate cortex (V1) and forms the posterior border of V2. The representation of the horizontal meridian in V2 forms the anterior border of V2 and is split so that the representation of the lower visual field is located dorsally and that of the upper field ventrally. As in V1, the representation of the central visual field is magnified relative to that of the periphery. The area of V2 is slightly smaller than that of V1. At a given eccentricity, receptive field size in V2 is larger than in V1. The myeloarchitecture of V2 is distinguishable from that of the surrounding cortex. The location of V2 corresponds, at least approximately, to that of cytoarchitectonic Area OB. V2 is bordered anteriorly by several other areas containing representations of the visual field.

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PubMed1979

Visual receptive fields of units in the pulvinar of cebus monkey.

Visually driven units, isolated in the ventrolateral group -- Pv1g (109) and in subnucleus Pmu (33) of the pulvinar of the cebus monkey, were studied in acute and chronic preparations under nitrous oxide N2O/O2 anesthesia during periods of EEG arousal. Taking into consideration the response properties to static or moving stimuli as well as the organization of the receptive fields, units isolated in the pulvinar were subdivided into 8 groups. Units displaying dynamic properties predominate over static ones. Static units were classified in 3 groups; of these, one showed uniform receptive fields; the remaining two groups, with non-uniform RFs, were further subdivided in terms of orientation selectivity. By testing for directional sensitivity, organization of the RFs and orientation selectivity, the dynamic units were divided in 5 groups. Among these there was a predominance of directional units, displaying uniform RFs and showing orientation selectivity. Although the receptive fields would extend into the ipsilateral hemifield (up to 10 degrees), their centers were always located in the contralateral visual hemifield. Binocularly driven units predominate in both static and dynamic categories.

Animals↗
PubMed1978

Visuotopic organization of the cebus pulvinar: a double representation the contralateral hemifield.

The projection of the visual field in the pulvinar nucleus was studied in 17 Cebus monkeys using electrophysiological techniques. Visual space is represented in two regions of the pulvinar; (1) the ventrolateral group, Pvlg, comprising nuclei P delta, P delta, P gamma, P eta and P mu 1; and (2) P mu. In the first group, which corresponds to the pulvinar inferior and ventral part of the pulvinar lateralis, we observed a greater respresentation of the central part of the visual field. Approximately 58% of the volume of the ventrolateral group is concerned with the visual space within 10 degrees of the fovea. This portion of the visual field is represented at its lateral aspects, mainly close to the level of the caudal pole of the lateral geniculate nucleus (LGN). Projection of the vertical meridian runs along its lateral border while that of the horizontal one is found running from the dorsal third of the LGN's hilus to the medial border of the ventro-lateral group. The lower quadrant is represented at its dorsal portion while the upper quadrant is represented at the ventral one. In Pmu the representation is rotated 90 degrees clockwise around the rostrocaudal axis: the vertical meridian is found at the ventromedial border of this nucleus. Thus, the lower quadrant is represented at the later portion of Pmu and the upper at its medial portion. Both projections are restricted to the contralateral hemifield.

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PubMedDate not supplied

Cortical afferents of visual area MT in the Cebus monkey: possible homologies between New and Old World monkeys.

Cortical projections to the middle temporal (MT) visual area were studied by injecting the retrogradely transported fluorescent tracer Fast Blue into MT in adult New World monkeys (Cebus apella). Injection sites were selected based on electrophysiological recordings, and covered eccentricities from 2-70 deg, in both the upper and lower visual fields. The position and laminar distribution of labeled cell bodies were correlated with myeloarchitectonic boundaries and displayed in flat reconstructions of the neocortex. Topographically organized projections were found to arise mainly from the primary, second, third, and fourth visual areas (V1, V2, V3, and V4). Coarsely topographic patterns were observed in transitional V4 (V4t), in the parieto-occipital and parieto-occipital medial areas (PO and POm), and in the temporal ventral posterior area (TVP). In addition, widespread or nontopographic label was found in visual areas of the superior temporal sulcus (medial superior temporal, MST, and fundus of superior temporal, FST), annectent gyrus (dorsointermediate area, DI; and dorsomedial area, DM), intraparietal sulcus (lateral intraparietal, LIP; posterior intraparietal, PIP; and ventral intraparietal, VIP), and in the frontal eye field (FEF). Label in PO, POm, and PIP was found only after injections in the representation of the peripheral visual field (> 10 deg), and label in V4 and FST was more extensive after injections in the central representation. The projections from V1 and V2 originated predominantly from neurons in supragranular layers, whereas those from V3, V4t, DM, DI, POm, and FEF consisted of intermixed patches with either supragranular or infragranular predominance. All of the other projections were predominantly infragranular. Invasion of area MST by the injection site led to the labeling of further pathways, including substantial projections from the dorsal prelunate area (DP) and from an ensemble of areas located along the medial wall of the hemisphere. In addition, weaker projections were observed from the parieto-occipital dorsal area (POd), area 7a, area prostriata, the posterior bank of the arcuate sulcus, and areas in the anterior part of the lateral sulcus. Despite the different nomenclatures and areal boundaries recognized by different models of simian cortical organization, the pattern of projections to area MT is remarkably similar among primates. Our results provide evidence for the existence of many homologous areas in the extrastriate visual cortex of New and Old World monkeys.

Afferent Pathways↗