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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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The middle temporal area (MT) of marmoset. (A) Photomicrograph of adjacent coronal sections, showing the histological distinctiveness of area MT revealed by myelin (left) and Nissl (right) stains. MT stands out as heavily myelinated in comparison with most cortical areas. Although the boundaries are less obvious, MT can also be identified in Nissl stained sections by the thinner and denser layer IV, and by the thicker layer VI, in comparison with adjacent areas. Scale bar = 1 mm. (B) Direction tuning for gratings and plaids in two representative directions elective MT neurons. The left panel illustrates the responses of a “component-cell,” which shows bi-lobed tuning for plaids, as if it responded to the individual gratings that comprise the plaid. The right panel shows the responses of a “pattern-cell,” which has similar direction tuning to gratings and plaids. (C) Spatial frequency tuning of a representative “component cell” in the peripheral representation of MT; the response to low spatial frequencies is neglible. (D) Tuning for the size of a patch of drifting grating, of optimal spatial frequency, showing large receptive field size of neurons in area MT. Scale bars in B show 20 impulses/s. (B–D) adapted from Solomon et al. (2011).
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Figure 6: The middle temporal area (MT) of marmoset. (A) Photomicrograph of adjacent coronal sections, showing the histological distinctiveness of area MT revealed by myelin (left) and Nissl (right) stains. MT stands out as heavily myelinated in comparison with most cortical areas. Although the boundaries are less obvious, MT can also be identified in Nissl stained sections by the thinner and denser layer IV, and by the thicker layer VI, in comparison with adjacent areas. Scale bar = 1 mm. (B) Direction tuning for gratings and plaids in two representative directions elective MT neurons. The left panel illustrates the responses of a “component-cell,” which shows bi-lobed tuning for plaids, as if it responded to the individual gratings that comprise the plaid. The right panel shows the responses of a “pattern-cell,” which has similar direction tuning to gratings and plaids. (C) Spatial frequency tuning of a representative “component cell” in the peripheral representation of MT; the response to low spatial frequencies is neglible. (D) Tuning for the size of a patch of drifting grating, of optimal spatial frequency, showing large receptive field size of neurons in area MT. Scale bars in B show 20 impulses/s. (B–D) adapted from Solomon et al. (2011).

Mentions: Area MT, which as in other primates is characterized by dense myelination (Spatz, 1977; Rosa and Elston, 1998; Bourne et al., 2007; Bock et al., 2009), lies posterior to the lateral sulcus (Figures 1 and Figures 6). Marmosets (and probably other species of Callitrichidae) are the only simian primates in which MT is entirely exposed on the surface of the cortex, creating unique opportunities for studies using imaging, intracellular or multielectrode array analyses. The size of MT in the marmoset is approximately 13 mm2 in each hemisphere, making it about 6.5% the size of V1; these estimates are similar to those in other simian primates (Pessoa et al., 1992; Rosa, 2002). The representation of the central visual field is less emphasized than in V1: whereas the central 5° around the fixation point project to about 40% of the volume of V1, the corresponding region only occupies 20% of MT (Rosa and Elston, 1998).


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

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

The middle temporal area (MT) of marmoset. (A) Photomicrograph of adjacent coronal sections, showing the histological distinctiveness of area MT revealed by myelin (left) and Nissl (right) stains. MT stands out as heavily myelinated in comparison with most cortical areas. Although the boundaries are less obvious, MT can also be identified in Nissl stained sections by the thinner and denser layer IV, and by the thicker layer VI, in comparison with adjacent areas. Scale bar = 1 mm. (B) Direction tuning for gratings and plaids in two representative directions elective MT neurons. The left panel illustrates the responses of a “component-cell,” which shows bi-lobed tuning for plaids, as if it responded to the individual gratings that comprise the plaid. The right panel shows the responses of a “pattern-cell,” which has similar direction tuning to gratings and plaids. (C) Spatial frequency tuning of a representative “component cell” in the peripheral representation of MT; the response to low spatial frequencies is neglible. (D) Tuning for the size of a patch of drifting grating, of optimal spatial frequency, showing large receptive field size of neurons in area MT. Scale bars in B show 20 impulses/s. (B–D) adapted from Solomon et al. (2011).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126041&req=5

Figure 6: The middle temporal area (MT) of marmoset. (A) Photomicrograph of adjacent coronal sections, showing the histological distinctiveness of area MT revealed by myelin (left) and Nissl (right) stains. MT stands out as heavily myelinated in comparison with most cortical areas. Although the boundaries are less obvious, MT can also be identified in Nissl stained sections by the thinner and denser layer IV, and by the thicker layer VI, in comparison with adjacent areas. Scale bar = 1 mm. (B) Direction tuning for gratings and plaids in two representative directions elective MT neurons. The left panel illustrates the responses of a “component-cell,” which shows bi-lobed tuning for plaids, as if it responded to the individual gratings that comprise the plaid. The right panel shows the responses of a “pattern-cell,” which has similar direction tuning to gratings and plaids. (C) Spatial frequency tuning of a representative “component cell” in the peripheral representation of MT; the response to low spatial frequencies is neglible. (D) Tuning for the size of a patch of drifting grating, of optimal spatial frequency, showing large receptive field size of neurons in area MT. Scale bars in B show 20 impulses/s. (B–D) adapted from Solomon et al. (2011).
Mentions: Area MT, which as in other primates is characterized by dense myelination (Spatz, 1977; Rosa and Elston, 1998; Bourne et al., 2007; Bock et al., 2009), lies posterior to the lateral sulcus (Figures 1 and Figures 6). Marmosets (and probably other species of Callitrichidae) are the only simian primates in which MT is entirely exposed on the surface of the cortex, creating unique opportunities for studies using imaging, intracellular or multielectrode array analyses. The size of MT in the marmoset is approximately 13 mm2 in each hemisphere, making it about 6.5% the size of V1; these estimates are similar to those in other simian primates (Pessoa et al., 1992; Rosa, 2002). The representation of the central visual field is less emphasized than in V1: whereas the central 5° around the fixation point project to about 40% of the volume of V1, the corresponding region only occupies 20% of MT (Rosa and Elston, 1998).

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
Related in: MedlinePlus