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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

Topographic maps activated from four monitor positions demonstrating frontolateral extent of visual field representation (bird2).Data displayed as in Fig 2. A and E shows the azimuth polar and activity map obtained when the stimulus was presented with monitor at 0° with respect to the eye. Similarly, B and F shows the maps of 30° stimulation, C and G shows the maps of 60° stimulation and D and H shows the maps of 90° stimulation. In the same order I and M, J and N, K and O, and L and P shows the elevation retinotopic polar maps and the corresponding activity maps in the visual wulst when stimulated with an elevation stimulus from the different monitor positions. Scale bar = 500 μm.
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pone.0124917.g003: Topographic maps activated from four monitor positions demonstrating frontolateral extent of visual field representation (bird2).Data displayed as in Fig 2. A and E shows the azimuth polar and activity map obtained when the stimulus was presented with monitor at 0° with respect to the eye. Similarly, B and F shows the maps of 30° stimulation, C and G shows the maps of 60° stimulation and D and H shows the maps of 90° stimulation. In the same order I and M, J and N, K and O, and L and P shows the elevation retinotopic polar maps and the corresponding activity maps in the visual wulst when stimulated with an elevation stimulus from the different monitor positions. Scale bar = 500 μm.

Mentions: Retinotopic maps were colour-coded with respect to the position of the stimulus eliciting this activation. The combined information of the magnitude of neuronal activation and retinotopy is displayed in so-called polar maps. The colour codes used to display the retinotopic polar maps are shown along with each polar map. Please note that the colors in the wulst maps (Figs 2 and 3) represent different visual field positions for different monitor positions. Since blue always represents the center of the monitor, it corresponds to e.g. 0°, +30°, +60° etc. of the visual field for the azimuth maps, and to +15° for the elevation maps. To display visual field proportions in the retinotopically activated brain areas, iso-azimuth and iso-elevation lines were calculated using a Matlab routine and superimposed on the retinotopic polar maps (Fig 4). These calculations were preceded by a thresholding procedure which selected all pixels within the activity patch that showed at least 30% of the peak response, all other pixels were discarded. This procedure is illustrated in Fig 4. Fig 4A–4D gives examples of thresholded activity patches from birds 1 and 3, Fig 4E–4H shows the calculated iso-azimuth/elevation lines, and Fig 4I–4L illustrates the overlay of the thresholded activity map with the retinotopic visual field contours.


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)

Topographic maps activated from four monitor positions demonstrating frontolateral extent of visual field representation (bird2).Data displayed as in Fig 2. A and E shows the azimuth polar and activity map obtained when the stimulus was presented with monitor at 0° with respect to the eye. Similarly, B and F shows the maps of 30° stimulation, C and G shows the maps of 60° stimulation and D and H shows the maps of 90° stimulation. In the same order I and M, J and N, K and O, and L and P shows the elevation retinotopic polar maps and the corresponding activity maps in the visual wulst when stimulated with an elevation stimulus from the different monitor positions. Scale bar = 500 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390349&req=5

pone.0124917.g003: Topographic maps activated from four monitor positions demonstrating frontolateral extent of visual field representation (bird2).Data displayed as in Fig 2. A and E shows the azimuth polar and activity map obtained when the stimulus was presented with monitor at 0° with respect to the eye. Similarly, B and F shows the maps of 30° stimulation, C and G shows the maps of 60° stimulation and D and H shows the maps of 90° stimulation. In the same order I and M, J and N, K and O, and L and P shows the elevation retinotopic polar maps and the corresponding activity maps in the visual wulst when stimulated with an elevation stimulus from the different monitor positions. Scale bar = 500 μm.
Mentions: Retinotopic maps were colour-coded with respect to the position of the stimulus eliciting this activation. The combined information of the magnitude of neuronal activation and retinotopy is displayed in so-called polar maps. The colour codes used to display the retinotopic polar maps are shown along with each polar map. Please note that the colors in the wulst maps (Figs 2 and 3) represent different visual field positions for different monitor positions. Since blue always represents the center of the monitor, it corresponds to e.g. 0°, +30°, +60° etc. of the visual field for the azimuth maps, and to +15° for the elevation maps. To display visual field proportions in the retinotopically activated brain areas, iso-azimuth and iso-elevation lines were calculated using a Matlab routine and superimposed on the retinotopic polar maps (Fig 4). These calculations were preceded by a thresholding procedure which selected all pixels within the activity patch that showed at least 30% of the peak response, all other pixels were discarded. This procedure is illustrated in Fig 4. Fig 4A–4D gives examples of thresholded activity patches from birds 1 and 3, Fig 4E–4H shows the calculated iso-azimuth/elevation lines, and Fig 4I–4L illustrates the overlay of the thresholded activity map with the retinotopic visual field contours.

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