Löwel, Siegrid

[["dc.bibliographiccitation.artnumber","e0124917"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","PLoS ONE"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Michael, Neethu"],["dc.contributor.author","Loewel, Siegrid"],["dc.contributor.author","Bischof, Hans-Joachim"],["dc.date.accessioned","2018-11-07T09:58:36Z"],["dc.date.available","2018-11-07T09:58:36Z"],["dc.date.issued","2015"],["dc.description.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 auto-fluorescent 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 degrees beyond the beak tip up to +125 degrees laterally. Vertically, a small strip from -10 degrees below to about +25 degrees 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."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2015"],["dc.identifier.doi","10.1371/journal.pone.0124917"],["dc.identifier.isi","000352478400148"],["dc.identifier.pmid","25853253"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11761"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37397"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Public Library Science"],["dc.relation.issn","1932-6203"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0"],["dc.title","Features of the Retinotopic Representation in the Visual Wulst of a Laterally Eyed Bird, the Zebra Finch (Taeniopygia guttata)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e0154927"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","PLoS ONE"],["dc.bibliographiccitation.volume","11"],["dc.contributor.author","Bischof, Hans-Joachim"],["dc.contributor.author","Eckmeier, Dennis"],["dc.contributor.author","Keary, Nina"],["dc.contributor.author","Loewel, Siegrid"],["dc.contributor.author","Mayer, Uwe"],["dc.contributor.author","Michael, Neethu"],["dc.date.accessioned","2018-11-07T10:14:27Z"],["dc.date.available","2018-11-07T10:14:27Z"],["dc.date.issued","2016"],["dc.description.abstract","The visual wulst is the telencephalic target of the avian thalamofugal visual system. It contains several retinotopically organised representations of the contralateral visual field. We used optical imaging of intrinsic signals, electrophysiological recordings, and retrograde tracing with two fluorescent tracers to evaluate properties of these representations in the zebra finch, a songbird with laterally placed eyes. Our experiments revealed that there is some variability of the neuronal maps between individuals and also concerning the number of detectable maps. It was nonetheless possible to identify three different maps, a posterolateral, a posteromedial, and an anterior one, which were quite constant in their relation to each other. The posterolateral map was in contrast to the two others constantly visible in each successful experiment. The topography of the two other maps was mirrored against that map. Electrophysiological recordings in the anterior and the posterolateral map revealed that all units responded to flashes and to moving bars. Mean directional preferences as well as latencies were different between neurons of the two maps. Tracing experiments confirmed previous reports on the thalamo-wulst connections and showed that the anterior and the posterolateral map receive projections from separate clusters within the thalamic nuclei. Maps are connected to each other by wulst intrinsic projections. Our experiments confirm that the avian visual wulst contains several separate retinotopic maps with both different physiological properties and different thalamo-wulst afferents. This confirms that the functional organization of the visual wulst is very similar to its mammalian equivalent, the visual cortex."],["dc.identifier.doi","10.1371/journal.pone.0154927"],["dc.identifier.isi","000375675700076"],["dc.identifier.pmid","27139912"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13251"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40621"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Public Library Science"],["dc.relation.issn","1932-6203"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0"],["dc.title","Multiple Visual Field Representations in the Visual Wulst of a Laterally Eyed Bird, the Zebra Finch (Taeniopygia guttata)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e85225"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","PLoS ONE"],["dc.bibliographiccitation.volume","9"],["dc.contributor.author","Michael, Neethu"],["dc.contributor.author","Bischof, Hans-Joachim"],["dc.contributor.author","Loewel, Siegrid"],["dc.date.accessioned","2018-11-07T09:45:13Z"],["dc.date.available","2018-11-07T09:45:13Z"],["dc.date.issued","2014"],["dc.description.abstract","Large-scale brain activity patterns can be visualized by optical imaging of intrinsic signals (OIS) based on activity-dependent changes in the blood oxygenation level. Another method, flavoprotein autofluorescence imaging (AFI), exploits the mitochondrial flavoprotein autofluorescence, which is enhanced during neuronal activity. In birds, topographic mapping of visual space has been shown in the visual wulst, the avian homologue of the mammalian visual cortex by using OIS. We here applied the AFI method to visualize topographic maps in the visual wulst because with OIS, which depends on blood flow changes, blood vessel artifacts often obscure brain activity maps. We then compared both techniques quantitatively in zebra finches and in C57Bl/6J mice using the same setup and stimulation conditions. In addition to experiments with craniotomized animals, we also examined mice with intact skull (in zebra finches, intact skull imaging is not feasible probably due to the skull construction). In craniotomized animals, retinotopic maps were obtained by both methods in both species. Using AFI, artifacts caused by blood vessels were generally reduced, the magnitude of neuronal activity significantly higher and the retinotopic map quality better than that obtained by OIS in both zebra finches and mice. In contrast, our measurements in non-craniotomized mice did not reveal any quantitative differences between the two methods. Our results thus suggest that AFI is the method of choice for investigations of visual processing in zebra finches. In mice, however, if researchers decide to use the advantages of imaging through the intact skull, they will not be able to exploit the higher signals obtainable by the AFI-method."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2014"],["dc.identifier.doi","10.1371/journal.pone.0085225"],["dc.identifier.isi","000329462700064"],["dc.identifier.pmid","24400130"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9661"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34567"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Public Library Science"],["dc.relation.issn","1932-6203"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0"],["dc.title","Flavoprotein Autofluorescence Imaging of Visual System Activity in Zebra Finches and Mice"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e11912"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","PloS one"],["dc.bibliographiccitation.lastpage","e11912"],["dc.bibliographiccitation.volume","5"],["dc.contributor.author","Keary, Nina"],["dc.contributor.author","Voss, Joe"],["dc.contributor.author","Lehmann, Konrad"],["dc.contributor.author","Bischof, Hans-Joachim"],["dc.contributor.author","Löwel, Siegrid"],["dc.date.accessioned","2019-07-09T11:53:19Z"],["dc.date.available","2019-07-09T11:53:19Z"],["dc.date.issued","2010"],["dc.description.abstract","BACKGROUND: The primary visual cortex of mammals is characterised by a retinotopic representation of the visual field. It has therefore been speculated that the visual wulst, the avian homologue of the visual cortex, also contains such a retinotopic map. We examined this for the first time by optical imaging of intrinsic signals in zebra finches, a small songbird with laterally placed eyes. In addition to the visual wulst, we visualised the retinotopic map of the optic tectum which is homologue to the superior colliculus in mammals. METHODOLOGY/PRINCIPAL FINDINGS: For the optic tectum, our results confirmed previous accounts of topography based on anatomical studies and conventional electrophysiology. Within the visual wulst, the retinotopy revealed by our experiments has not been illustrated convincingly before. The frontal part of the visual field (0 degrees +/-30 degrees azimuth) was not represented in the retinotopic map. The visual field from 30 degrees -60 degrees azimuth showed stronger magnification compared with more lateral regions. Only stimuli within elevations between about 20 degrees and 40 degrees above the horizon elicited neuronal activation. Activation from other elevations was masked by activation of the preferred region. Most interestingly, we observed more than one retinotopic representation of visual space within the visual wulst, which indicates that the avian wulst, like the visual cortex in mammals, may show some compartmentation parallel to the surface in addition to its layered structure. CONCLUSION/SIGNIFICANCE: Our results show the applicability of the optical imaging method also for small songbirds. We obtained a more detailed picture of retinotopic maps in birds, especially on the functional neuronal organisation of the visual wulst. Our findings support the notion of homology of visual wulst and visual cortex by showing that there is a functional correspondence between the two areas but also raise questions based on considerable differences between avian and mammalian retinotopic representations."],["dc.identifier.doi","10.1371/journal.pone.0011912"],["dc.identifier.fs","582119"],["dc.identifier.pmid","20694137"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/7274"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/60396"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","1932-6203"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.subject.mesh","Animals"],["dc.subject.mesh","Female"],["dc.subject.mesh","Male"],["dc.subject.mesh","Molecular Imaging"],["dc.subject.mesh","Optical Processes"],["dc.subject.mesh","Photic Stimulation"],["dc.subject.mesh","Songbirds"],["dc.subject.mesh","Superior Colliculi"],["dc.subject.mesh","Visual Cortex"],["dc.title","Optical imaging of retinotopic maps in a small songbird, the zebra finch."],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]