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A simpler primate brain: the visual system of the marmoset monkey.

Solomon SG, Rosa MG - Front Neural Circuits (2014)

Bottom Line: Therefore, in order to understand some aspects of human visual function, we need to study non-human primate brains.Which species is the most appropriate model?Here we review the visual pathways of the marmoset, highlighting recent work that brings these advantages into focus, and identify where additional work needs to be done to link marmoset brain organization to that of macaques and humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University College London London, UK.

ABSTRACT
Humans are diurnal primates with high visual acuity at the center of gaze. Although primates share many similarities in the organization of their visual centers with other mammals, and even other species of vertebrates, their visual pathways also show unique features, particularly with respect to the organization of the cerebral cortex. Therefore, in order to understand some aspects of human visual function, we need to study non-human primate brains. Which species is the most appropriate model? Macaque monkeys, the most widely used non-human primates, are not an optimal choice in many practical respects. For example, much of the macaque cerebral cortex is buried within sulci, and is therefore inaccessible to many imaging techniques, and the postnatal development and lifespan of macaques are prohibitively long for many studies of brain maturation, plasticity, and aging. In these and several other respects the marmoset, a small New World monkey, represents a more appropriate choice. Here we review the visual pathways of the marmoset, highlighting recent work that brings these advantages into focus, and identify where additional work needs to be done to link marmoset brain organization to that of macaques and humans. We will argue that the marmoset monkey provides a good subject for studies of a complex visual system, which will likely allow an important bridge linking experiments in animal models to humans.

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Location and visuotopic organization of marmoset primary visual cortex (V1). Top: caudal and medial views of the marmoset cerebral cortex, showing the location of V1 (red). The dashed line indicates the region reconstructed in the bottom panels. Middle: The representation of eccentricity from the fovea (“Ecc,” in degrees of visual angle), according to the color scale shown on the right. This reconstruction represents data from a single individual, in which hundreds of recording sites were obtained (Chaplin et al., 2013a). The portion of V1 exposed on the caudal surface of the brain corresponds to the representation of the fovea and parafovea (dark blue), while the far periphery of the visual field is represent at the most anterior portion of the calcarine sulcus (red). Bottom: The representation of polar angle (“Ang”) in the same individual. The lower contralateral visual field (blue, cyan) is found on the dorsal surface, and the upper contralateral field (yellow, orange, red) is found on the ventral surface. The representation of the horizontal meridian (green) divides V1 nearly equally.
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Figure 3: Location and visuotopic organization of marmoset primary visual cortex (V1). Top: caudal and medial views of the marmoset cerebral cortex, showing the location of V1 (red). The dashed line indicates the region reconstructed in the bottom panels. Middle: The representation of eccentricity from the fovea (“Ecc,” in degrees of visual angle), according to the color scale shown on the right. This reconstruction represents data from a single individual, in which hundreds of recording sites were obtained (Chaplin et al., 2013a). The portion of V1 exposed on the caudal surface of the brain corresponds to the representation of the fovea and parafovea (dark blue), while the far periphery of the visual field is represent at the most anterior portion of the calcarine sulcus (red). Bottom: The representation of polar angle (“Ang”) in the same individual. The lower contralateral visual field (blue, cyan) is found on the dorsal surface, and the upper contralateral field (yellow, orange, red) is found on the ventral surface. The representation of the horizontal meridian (green) divides V1 nearly equally.

Mentions: V1 is the largest single area in the marmoset brain, with a surface area of approximately 200 mm2 in each hemisphere (Pessoa et al., 1992; Missler et al., 1993a; Fritsches and Rosa, 1996). Marmoset V1 is also very large in relative terms in comparison with that in other species of monkey, including the macaque (20% versus 10% of the total area of the neocortex; Rosa and Tweedale, 2005; Chaplin et al., 2013b). The retinotopic map found in V1 of the marmoset is very similar to that described for the macaque and other diurnal primates (Fritsches and Rosa, 1996; Schira et al., 2012; Chaplin et al., 2013a; Figure 3). The foveal representation is highly magnified, occupying ∼20% of the surface area, and about 60% of V1 is dedicated to the central 10° of the visual field (Chaplin et al., 2013a). The peak magnification factor near the representation of the center of the fovea has been estimated to be 4–5 mm/degree, about 40% of the equivalent value in the macaque (Van Essen et al., 1984; Dow et al., 1985), and this proportional relationship is maintained throughout the visual field. The representations of the upper and lower contralateral quadrants are nearly symmetrical in size. As in other primates (e.g., Silveira et al., 1989; Azzopardi and Cowey, 1993), the magnification factor follows the sampling density of ganglion cells, but detailed analysis show that representation of the foveal field in V1 greatly exceeds that expected based from the retinal ganglion cell density (Chaplin et al., 2013a). This magnification of central vision in V1 is likely due to greater divergence in the retino-geniculo-cortical pathways serving foveal vision, compared to those serving peripheral vision (Chaplin et al., 2013a).


A simpler primate brain: the visual system of the marmoset monkey.

Solomon SG, Rosa MG - Front Neural Circuits (2014)

Location and visuotopic organization of marmoset primary visual cortex (V1). Top: caudal and medial views of the marmoset cerebral cortex, showing the location of V1 (red). The dashed line indicates the region reconstructed in the bottom panels. Middle: The representation of eccentricity from the fovea (“Ecc,” in degrees of visual angle), according to the color scale shown on the right. This reconstruction represents data from a single individual, in which hundreds of recording sites were obtained (Chaplin et al., 2013a). The portion of V1 exposed on the caudal surface of the brain corresponds to the representation of the fovea and parafovea (dark blue), while the far periphery of the visual field is represent at the most anterior portion of the calcarine sulcus (red). Bottom: The representation of polar angle (“Ang”) in the same individual. The lower contralateral visual field (blue, cyan) is found on the dorsal surface, and the upper contralateral field (yellow, orange, red) is found on the ventral surface. The representation of the horizontal meridian (green) divides V1 nearly equally.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 3: Location and visuotopic organization of marmoset primary visual cortex (V1). Top: caudal and medial views of the marmoset cerebral cortex, showing the location of V1 (red). The dashed line indicates the region reconstructed in the bottom panels. Middle: The representation of eccentricity from the fovea (“Ecc,” in degrees of visual angle), according to the color scale shown on the right. This reconstruction represents data from a single individual, in which hundreds of recording sites were obtained (Chaplin et al., 2013a). The portion of V1 exposed on the caudal surface of the brain corresponds to the representation of the fovea and parafovea (dark blue), while the far periphery of the visual field is represent at the most anterior portion of the calcarine sulcus (red). Bottom: The representation of polar angle (“Ang”) in the same individual. The lower contralateral visual field (blue, cyan) is found on the dorsal surface, and the upper contralateral field (yellow, orange, red) is found on the ventral surface. The representation of the horizontal meridian (green) divides V1 nearly equally.
Mentions: V1 is the largest single area in the marmoset brain, with a surface area of approximately 200 mm2 in each hemisphere (Pessoa et al., 1992; Missler et al., 1993a; Fritsches and Rosa, 1996). Marmoset V1 is also very large in relative terms in comparison with that in other species of monkey, including the macaque (20% versus 10% of the total area of the neocortex; Rosa and Tweedale, 2005; Chaplin et al., 2013b). The retinotopic map found in V1 of the marmoset is very similar to that described for the macaque and other diurnal primates (Fritsches and Rosa, 1996; Schira et al., 2012; Chaplin et al., 2013a; Figure 3). The foveal representation is highly magnified, occupying ∼20% of the surface area, and about 60% of V1 is dedicated to the central 10° of the visual field (Chaplin et al., 2013a). The peak magnification factor near the representation of the center of the fovea has been estimated to be 4–5 mm/degree, about 40% of the equivalent value in the macaque (Van Essen et al., 1984; Dow et al., 1985), and this proportional relationship is maintained throughout the visual field. The representations of the upper and lower contralateral quadrants are nearly symmetrical in size. As in other primates (e.g., Silveira et al., 1989; Azzopardi and Cowey, 1993), the magnification factor follows the sampling density of ganglion cells, but detailed analysis show that representation of the foveal field in V1 greatly exceeds that expected based from the retinal ganglion cell density (Chaplin et al., 2013a). This magnification of central vision in V1 is likely due to greater divergence in the retino-geniculo-cortical pathways serving foveal vision, compared to those serving peripheral vision (Chaplin et al., 2013a).

Bottom Line: Therefore, in order to understand some aspects of human visual function, we need to study non-human primate brains.Which species is the most appropriate model?Here we review the visual pathways of the marmoset, highlighting recent work that brings these advantages into focus, and identify where additional work needs to be done to link marmoset brain organization to that of macaques and humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University College London London, UK.

ABSTRACT
Humans are diurnal primates with high visual acuity at the center of gaze. Although primates share many similarities in the organization of their visual centers with other mammals, and even other species of vertebrates, their visual pathways also show unique features, particularly with respect to the organization of the cerebral cortex. Therefore, in order to understand some aspects of human visual function, we need to study non-human primate brains. Which species is the most appropriate model? Macaque monkeys, the most widely used non-human primates, are not an optimal choice in many practical respects. For example, much of the macaque cerebral cortex is buried within sulci, and is therefore inaccessible to many imaging techniques, and the postnatal development and lifespan of macaques are prohibitively long for many studies of brain maturation, plasticity, and aging. In these and several other respects the marmoset, a small New World monkey, represents a more appropriate choice. Here we review the visual pathways of the marmoset, highlighting recent work that brings these advantages into focus, and identify where additional work needs to be done to link marmoset brain organization to that of macaques and humans. We will argue that the marmoset monkey provides a good subject for studies of a complex visual system, which will likely allow an important bridge linking experiments in animal models to humans.

Show MeSH