The ipsilateral field representation in the striate cortex of the opossum

Volchan, Eliane; Bernardes, R. F.; Rocha‐Miranda, Carlos Eduardo; Gleiser, L; Gawryszewski, Luiz G.

doi:10.1007/bf00248221

Cited by 21 publications

(12 citation statements)

References 20 publications

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“…The topographic organization of V1 has been described in a few species of marsupial including the quoll , wallaby (Vidyasagar et al, 1992), and opossum (Sousa et al, 1978;Volchan et al, 1988). In each of these species, the periphery of the visual field was represented in medial portions of V1, the upper quadrant was represented caudally, and the lower quadrant was represented rostrally.…”

Section: V1supporting

confidence: 72%

Organization and connections of V1 inMonodelphis domestica

2000

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We examined the internal organization and connections of the primary visual area, V1, in the South American marsupial Monodelphis domestica. Multiunit electrophysiological recording techniques were used to record from neurons at multiple sites. Receptive field location, size, progressions, and reversals were systematically examined to determine the visuotopic organization of V1 and its boundaries with adjacent visual areas. As in other mammals, a virtually complete representation of the visual hemifield was observed in V1, which was coextensive with a region of dense myelination. The vertical meridian was represented at the rostrolateral boundary of the field, the upper visual quadrant was represented caudolaterally, whereas the lower visual quadrant was represented rostromedially. Injections of fluorescent tracers into V1 revealed dense connections with cortex immediately adjacent to the rostrolateral boundary, in peristriate cortex (PS or V2). Connections were also consistently observed with a caudotemporal area (CT), entorhinal cortex (EC), and multimodal cortex (auditory/visual, A/V). These results demonstrate that M. domestica possess a highly differentiated neocortex with clear functional and architectonic cortical field boundaries, as well as discrete patterns of cortical connections. Some connections of V1 are similar to those observed in eutherian mammals, such as connections with V2 and extrastriate areas (e.g., CT), which suggests that there are general features of visual system organization that all mammals possess due to retention from a common ancestor. On the other hand, connections of V1 with EC and multimodal cortex may be a primitive feature of visual cortex that was lost in some lineages, may be a derived feature of marsupial neocortex, or may be a feature particular to mammals with small brains.

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Section: V1supporting

confidence: 72%

Organization and connections of V1 inMonodelphis domestica

2000

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“…The retino-topic organization of V1 in short-tailed opossums is similar to that found in other marsupials, such as the South American opossum [Sousa et al, 1978; Volchan et al, 1988], Virginia opossum [Kaas, 1980], quoll [Rosa et al, 1999], and wallaby [Vidyasagar et al, 1992], and other mammals [Kaas, 1980]. Area 17 of short-tailed opossums is easily identified as an area with a layer 4 that is densely populated with granule cells and is densely myelinated [Kahn et al, 2000].…”

Section: Discussionmentioning

confidence: 60%

An Architectonic Study of the Neocortex of the Short-Tailed Opossum <i>(Monodelphis domestica)</i>

Wong

Kaas²

2009

Brain Behav Evol

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Short-tailed opossums (Monodelphis domestica) belong to the branch of marsupial mammals that diverged from eutherian mammals approximately 180 million years ago. They are small in size, lack a marsupial pouch, and may have retained more morphological characteristics of early marsupial neocortex than most other marsupials. In the present study, we used several different histochemical and immunochemical procedures to reveal the architectonic characteristics of cortical areas in short-tailed opossums. Subdivisions of cortex were identified in brain sections cut in the coronal, sagittal, horizontal or tangential planes and processed for a calcium-binding protein, parvalbumin (PV), neurofilament protein epitopes recognized by SMI-32, the vesicle glutamate transporter 2 (VGluT2), myelin, cytochrome oxidase (CO), and Nissl substance. These different procedures revealed similar boundaries among areas, suggesting that functionally relevant borders were detected. The results allowed a fuller description and more precise demarcation of previously identified sensory areas, and the delineation of additional subdivisions of cortex. Area 17 (V1) was especially prominent, with a densely populated layer 4, high myelination levels, and dark staining of PV and VGluT2 immunopositive terminations. These architectonic features were present, albeit less pronounced, in somatosensory and auditory cortex. The major findings support the conclusion that short-tailed opossums have fewer cortical areas and their neocortex is less distinctly laminated than most other mammals.

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“…However, we are not aware of any study of nasotemporal overlap in the marmoset. The representation of the ipsilateral field in V1 also exists in other mammals, where it tends to be larger than in primates (Clarke and Whitteridge, 1976;Volchan et al, 1988;Payne, 1990;Rosa et al, 1993). In the cat, Payne (1990) found evidence for both the callosal and the retinofugal pathways contributing to the ipsilateral representation in V1 and suggested that the two routes might operate synergistically.…”

Section: Ipsilateral Visual Field Representationmentioning

confidence: 88%

Visuotopic organisation of striate cortex in the marmoset monkey (Callithrix jacchus)

Fritsches

Rosa

1996

J. Comp. Neurol.

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The visuotopic organisation of the primary visual cortex (V1) was studied by extracellular recordings in adult male marmosets (Callithrix jacchus) that were anaesthetised with sufentanil/nitrous oxide and paralysed with pancuronium bromide. Extensive sampling of the occipital region in four individuals and partial coverage of V1 in five others allowed not only the establishment of the normal visuotopy but also the study of interindividual variability. As in other primates, there was a single, continuous map of the contralateral hemifield in V1, with the upper visual quadrant represented ventrally and the lower quadrant represented dorsally. The surface area of V1, which was measured in two-dimensional reconstructions of the cortical surface, varied from 192 to 217 mm2. There was a marked emphasis on the representation of the foveal and parafoveal visual fields: the representation of the central 5 degrees of the visual field occupied 36-39% of the surface area of V1, whereas the central 10 degrees occupied 57-59%. No asymmetry between the representations of the upper and lower quadrants was apparent. The visual topography of V1 was highly consistent between individuals, relative to both sulcal landmarks and stereotaxic coordinates. The entire contralateral hemifield was represented in V1; in addition, neurones with receptive fields whose borders invaded the ipsilateral hemifield were observed within V1, less than 800 microns from the V1/V2 boundary. The total invasion of the ipsilateral hemifield was less than 0.5 degree at the centre of the fovea but reached 8 degrees at the periphery of the vertical meridian. Our results demonstrate that the organisation of V1 is similar in diurnal New and Old World simians, despite major variations in size, ecological niche, and timing of postnatal development across species.

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The ipsilateral field representation in the striate cortex of the opossum

Cited by 21 publications

References 20 publications

Organization and connections of V1 inMonodelphis domestica

Organization and connections of V1 inMonodelphis domestica

An Architectonic Study of the Neocortex of the Short-Tailed Opossum <i>(Monodelphis domestica)</i>

Visuotopic organisation of striate cortex in the marmoset monkey (Callithrix jacchus)

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