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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

Demonstration of the lack of foveal overrepresentation.X-axis represents the various 10° wide segments of the visual field. Y axis shows the number of pixels (1 pixel = 8.89 μm) contained in the activated area. Open circles denote individual values, horizontal red lines the means of the various segments. The open blue arrow points to the segment including the foveal representation (denoted by ‘F’). There was no significant difference between the pixel numbers in the different segments. Data from five birds are illustrated.
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pone.0124917.g006: Demonstration of the lack of foveal overrepresentation.X-axis represents the various 10° wide segments of the visual field. Y axis shows the number of pixels (1 pixel = 8.89 μm) contained in the activated area. Open circles denote individual values, horizontal red lines the means of the various segments. The open blue arrow points to the segment including the foveal representation (denoted by ‘F’). There was no significant difference between the pixel numbers in the different segments. Data from five birds are illustrated.

Mentions: Further comparison of the results from the different monitor positions revealed some interesting features of the intrinsic organization of the topographic representations. In mammals, as mentioned above, an overrepresentation of the foveal area has been found frequently. We therefore evaluated a potential foveal overrepresentation and also the interindividual variability of the maps between different birds by calculating the size of the areas between the azimuth lines of 10° distance along the topographic representation from -5° frontally to +95° along the horizon. Fig 6 illustrates large inter-individual differences in area sizes but no detectable foveal overrepresentation (indicated by an open blue arrow; (ANOVA, F (9, 44) = 0.7781, p = 0.6372). We also calculated the area of the activity patch induced in the visual wulst by peripheral (0°+90°) or foveal stimulation (30°+60°) (azimuth, peripheral: 0.6±0.2 mm2, foveal: 0.8±0.1 mm2; elevation, peripheral: 0.7±0.2 mm2, foveal: 0.9±0.2 mm2). Yet again there was no difference between the area sizes (repeated measures ANOVA, F (3, 6) = 0.8216, p = 0.4677).


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)

Demonstration of the lack of foveal overrepresentation.X-axis represents the various 10° wide segments of the visual field. Y axis shows the number of pixels (1 pixel = 8.89 μm) contained in the activated area. Open circles denote individual values, horizontal red lines the means of the various segments. The open blue arrow points to the segment including the foveal representation (denoted by ‘F’). There was no significant difference between the pixel numbers in the different segments. Data from five birds are illustrated.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0124917.g006: Demonstration of the lack of foveal overrepresentation.X-axis represents the various 10° wide segments of the visual field. Y axis shows the number of pixels (1 pixel = 8.89 μm) contained in the activated area. Open circles denote individual values, horizontal red lines the means of the various segments. The open blue arrow points to the segment including the foveal representation (denoted by ‘F’). There was no significant difference between the pixel numbers in the different segments. Data from five birds are illustrated.
Mentions: Further comparison of the results from the different monitor positions revealed some interesting features of the intrinsic organization of the topographic representations. In mammals, as mentioned above, an overrepresentation of the foveal area has been found frequently. We therefore evaluated a potential foveal overrepresentation and also the interindividual variability of the maps between different birds by calculating the size of the areas between the azimuth lines of 10° distance along the topographic representation from -5° frontally to +95° along the horizon. Fig 6 illustrates large inter-individual differences in area sizes but no detectable foveal overrepresentation (indicated by an open blue arrow; (ANOVA, F (9, 44) = 0.7781, p = 0.6372). We also calculated the area of the activity patch induced in the visual wulst by peripheral (0°+90°) or foveal stimulation (30°+60°) (azimuth, peripheral: 0.6±0.2 mm2, foveal: 0.8±0.1 mm2; elevation, peripheral: 0.7±0.2 mm2, foveal: 0.9±0.2 mm2). Yet again there was no difference between the area sizes (repeated measures ANOVA, F (3, 6) = 0.8216, p = 0.4677).

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