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Features of the retinotopic representation in the visual wulst of a laterally eyed bird, the zebra finch (Taeniopygia guttata).

Michael N, Löwel S, Bischof HJ - PLoS ONE (2015)

Bottom Line: We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye.This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye.Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.

View Article: PubMed Central - PubMed

Affiliation: Department of Systems Neuroscience, Johann-Friedrich-Blumenbach Institut für Zoologie und Anthropologie, Universität Göttingen, Göttingen, Germany; Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences (GGNB), Göttingen, Germany.

ABSTRACT
The visual wulst of the zebra finch comprises at least two retinotopic maps of the contralateral eye. As yet, it is not known how much of the visual field is represented in the wulst neuronal maps, how the organization of the maps is related to the retinal architecture, and how information from the ipsilateral eye is involved in the activation of the wulst. Here, we have used autofluorescent flavoprotein imaging and classical anatomical methods to investigate such characteristics of the most posterior map of the multiple retinotopic representations. We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye. Horizontally, the visual field representation extended from -5° beyond the beak tip up to +125° laterally. Vertically, a small strip from -10° below to about +25° above the horizon activated the visual wulst. Although retinal ganglion cells had a much higher density around the fovea and along a strip extending from the fovea towards the beak tip, these areas were not overrepresented in the wulst map. The wulst area activated from the foveal region of the ipsilateral eye, overlapped substantially with the middle of the three contralaterally activated regions in the visual wulst, and partially with the other two. Visual wulst activity evoked by stimulation of the frontal visual field was stronger with contralateral than with binocular stimulation. This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye. The lack of a foveal overrepresentation suggests that identification of objects may not be the primary task of the zebra finch visual wulst. Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.

No MeSH data available.


Related in: MedlinePlus

Retinal ganglion cell density measurements and landmark determination.A—Density distribution of retinal ganglion cells. The plot is adjusted in size and rotation to fit the landmark measurements in Fig 7B. P- pecten, F-fovea, Black arrow- area of higher density extending from the fovea into the direction of the beak. Scale bar: number of retinal ganglion cells/ mm2. B- Schematic representation of the positioning of the regions of higher ganglion densities with respect to visual field. P-pecten, F-fovea, B-beak indicated a red filled circle, yellow oval and ‘?’- area of higher density extending from the fovea into the direction of the beak. C- Horizontal section of the eyeball. Arrow depicts the axial length measured from the cornea to the retina. Scale bar = 1 mm. D-F—Sections at different locations along a section of retina (as indicated in Fig 7C), GCL-ganglion cell layer, INL-inner nuclear layer, ONL-outer nuclear layer, RPE-retinal pigmental epithelium, PR-photoreceptors. D-Fovea, E- medial between fovea and ora serrata, F- near the rim of the retina. Scale bar for D-F = 50 μm.
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pone.0124917.g007: Retinal ganglion cell density measurements and landmark determination.A—Density distribution of retinal ganglion cells. The plot is adjusted in size and rotation to fit the landmark measurements in Fig 7B. P- pecten, F-fovea, Black arrow- area of higher density extending from the fovea into the direction of the beak. Scale bar: number of retinal ganglion cells/ mm2. B- Schematic representation of the positioning of the regions of higher ganglion densities with respect to visual field. P-pecten, F-fovea, B-beak indicated a red filled circle, yellow oval and ‘?’- area of higher density extending from the fovea into the direction of the beak. C- Horizontal section of the eyeball. Arrow depicts the axial length measured from the cornea to the retina. Scale bar = 1 mm. D-F—Sections at different locations along a section of retina (as indicated in Fig 7C), GCL-ganglion cell layer, INL-inner nuclear layer, ONL-outer nuclear layer, RPE-retinal pigmental epithelium, PR-photoreceptors. D-Fovea, E- medial between fovea and ora serrata, F- near the rim of the retina. Scale bar for D-F = 50 μm.

Mentions: Fig 7 depicts the results of our retinal ganglion cell density measurements and the determination of the retinal landmarks by ophthalmoscopic investigation. Three zebra finches were used for this study. The calculated retinal ganglion cell density map is illustrated in Fig 7A; where in the visual field these regions of higher ganglion densities were present is illustrated schematically in Fig 7B. It shows the position of the retinal landmarks appearing as if projected through the lens onto a virtual globe representing the visual space. This means that the measurements of the fovea appear in the direction where the fovea is looking. The pecten is located ventrally in the eye, so its position in the visual field is dorsally, indicating that the pecten occludes the view of a substantial part of the dorsal visual field. Small red circles, marked by “F” indicate the foveal high density region of Fig 7A, the yellow oval corresponds to the second high density region, and the area where the pecten is positioned is shown in green. Fig 7C shows a cross-section through the whole eye, including an arrow that marks the distance used for the transformation of visual angles into distances on the retina; and Fig 7D–7F show examples of retinal cross-sections that were used for reconstructing the density map in A. In the cross sections, one can easily discern 4 layers containing cell bodies, with the ganglion cell layer (GCL) being the uppermost and relatively thin layer in each of the pictures. The density map (Fig 7A) shows how retinal ganglion cell density decreases from the fovea, which appears as a deep tapered depression in the retina (Fig 7D), to more peripheral regions (Fig 7E and 7F).


Features of the retinotopic representation in the visual wulst of a laterally eyed bird, the zebra finch (Taeniopygia guttata).

Michael N, Löwel S, Bischof HJ - PLoS ONE (2015)

Retinal ganglion cell density measurements and landmark determination.A—Density distribution of retinal ganglion cells. The plot is adjusted in size and rotation to fit the landmark measurements in Fig 7B. P- pecten, F-fovea, Black arrow- area of higher density extending from the fovea into the direction of the beak. Scale bar: number of retinal ganglion cells/ mm2. B- Schematic representation of the positioning of the regions of higher ganglion densities with respect to visual field. P-pecten, F-fovea, B-beak indicated a red filled circle, yellow oval and ‘?’- area of higher density extending from the fovea into the direction of the beak. C- Horizontal section of the eyeball. Arrow depicts the axial length measured from the cornea to the retina. Scale bar = 1 mm. D-F—Sections at different locations along a section of retina (as indicated in Fig 7C), GCL-ganglion cell layer, INL-inner nuclear layer, ONL-outer nuclear layer, RPE-retinal pigmental epithelium, PR-photoreceptors. D-Fovea, E- medial between fovea and ora serrata, F- near the rim of the retina. Scale bar for D-F = 50 μm.
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Related In: Results  -  Collection

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pone.0124917.g007: Retinal ganglion cell density measurements and landmark determination.A—Density distribution of retinal ganglion cells. The plot is adjusted in size and rotation to fit the landmark measurements in Fig 7B. P- pecten, F-fovea, Black arrow- area of higher density extending from the fovea into the direction of the beak. Scale bar: number of retinal ganglion cells/ mm2. B- Schematic representation of the positioning of the regions of higher ganglion densities with respect to visual field. P-pecten, F-fovea, B-beak indicated a red filled circle, yellow oval and ‘?’- area of higher density extending from the fovea into the direction of the beak. C- Horizontal section of the eyeball. Arrow depicts the axial length measured from the cornea to the retina. Scale bar = 1 mm. D-F—Sections at different locations along a section of retina (as indicated in Fig 7C), GCL-ganglion cell layer, INL-inner nuclear layer, ONL-outer nuclear layer, RPE-retinal pigmental epithelium, PR-photoreceptors. D-Fovea, E- medial between fovea and ora serrata, F- near the rim of the retina. Scale bar for D-F = 50 μm.
Mentions: Fig 7 depicts the results of our retinal ganglion cell density measurements and the determination of the retinal landmarks by ophthalmoscopic investigation. Three zebra finches were used for this study. The calculated retinal ganglion cell density map is illustrated in Fig 7A; where in the visual field these regions of higher ganglion densities were present is illustrated schematically in Fig 7B. It shows the position of the retinal landmarks appearing as if projected through the lens onto a virtual globe representing the visual space. This means that the measurements of the fovea appear in the direction where the fovea is looking. The pecten is located ventrally in the eye, so its position in the visual field is dorsally, indicating that the pecten occludes the view of a substantial part of the dorsal visual field. Small red circles, marked by “F” indicate the foveal high density region of Fig 7A, the yellow oval corresponds to the second high density region, and the area where the pecten is positioned is shown in green. Fig 7C shows a cross-section through the whole eye, including an arrow that marks the distance used for the transformation of visual angles into distances on the retina; and Fig 7D–7F show examples of retinal cross-sections that were used for reconstructing the density map in A. In the cross sections, one can easily discern 4 layers containing cell bodies, with the ganglion cell layer (GCL) being the uppermost and relatively thin layer in each of the pictures. The density map (Fig 7A) shows how retinal ganglion cell density decreases from the fovea, which appears as a deep tapered depression in the retina (Fig 7D), to more peripheral regions (Fig 7E and 7F).

Bottom Line: We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye.This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye.Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.

View Article: PubMed Central - PubMed

Affiliation: Department of Systems Neuroscience, Johann-Friedrich-Blumenbach Institut für Zoologie und Anthropologie, Universität Göttingen, Göttingen, Germany; Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences (GGNB), Göttingen, Germany.

ABSTRACT
The visual wulst of the zebra finch comprises at least two retinotopic maps of the contralateral eye. As yet, it is not known how much of the visual field is represented in the wulst neuronal maps, how the organization of the maps is related to the retinal architecture, and how information from the ipsilateral eye is involved in the activation of the wulst. Here, we have used autofluorescent flavoprotein imaging and classical anatomical methods to investigate such characteristics of the most posterior map of the multiple retinotopic representations. We found that the visual wulst can be activated by visual stimuli from a large part of the visual field of the contralateral eye. Horizontally, the visual field representation extended from -5° beyond the beak tip up to +125° laterally. Vertically, a small strip from -10° below to about +25° above the horizon activated the visual wulst. Although retinal ganglion cells had a much higher density around the fovea and along a strip extending from the fovea towards the beak tip, these areas were not overrepresented in the wulst map. The wulst area activated from the foveal region of the ipsilateral eye, overlapped substantially with the middle of the three contralaterally activated regions in the visual wulst, and partially with the other two. Visual wulst activity evoked by stimulation of the frontal visual field was stronger with contralateral than with binocular stimulation. This confirms earlier electrophysiological studies indicating an inhibitory influence of the activation of the ipsilateral eye on wulst activity elicited by stimulating the contralateral eye. The lack of a foveal overrepresentation suggests that identification of objects may not be the primary task of the zebra finch visual wulst. Instead, this brain area may be involved in the processing of visual information necessary for spatial orientation.

No MeSH data available.


Related in: MedlinePlus