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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 179 (1996), S. 785-795 
    ISSN: 1432-1351
    Keywords: Birds ; Visual system ; Tectofugal pathway ; Extrastriate cortex ; Mammals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The responses of single cells to computer-generated spots, bars, gratings, and motion-in-depth stimuli were studied in the ectostriatum and the adjacent neostriatum of the zebra finch, Taeniopygia guttata. No differences in neuronal properties could be detected between ectostriatum and neostriatum. The receptive fields of ectostriatal neurons are large, often extending over the entire visual field of the contralateral eye, and have oddly defined borders. The centers of the receptive fields, located in the foveal region, generally yielded better responses than the periphery, and exhibited different subdivisions. Neurons responded selectively to moving bars, preferring those moving parallel to their longest axis. An SDO (sensitivity, direction, orientation) analysis of responses to sinusoidal gratings showed that all orientations were equally represented by ectostriatal neurons, while there was a slight preference for forward and upward movements. The neurons also showed preferences for gratings of a particular spatial frequency, and responded vigorously to stimuli moving towards the eye (“looming”). Our results indicate that the ectostriatum is involved in both detecting displacement of the surround and in stimulus identification. By comparison with results obtained in the extrastriate cortex of mammals, it is concluded that the homology of the ectostriatum with the extrastriate cortex of mammals, which was proposed on the basis of hodological findings, is supported by our study.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 185 (1999), S. 69-79 
    ISSN: 1432-1351
    Keywords: Key words Birds ; Visual system ; Tectofugal pathway ; Topography ; Horizontal representation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Responses of neurons of the optic tectum, the prominent, highly laminated mesencephalic station of the tectofugal visual pathway in birds, to computer-generated and other visual stimuli were examined in zebra finches. Our study shows that the contralateral retina projects to the tectum in topographic order. The representation of the visual field is tilted against the horizon by 22°. The representation of the contralateral hemifield extends to the ipsilateral side by 15°. Most neurons have receptive fields with excitatory centres of different shapes and inhibitory surround. A new type of neuronal receptive field is described which has an excitatory centre and a surround which is movement sensitive and preferably excited by very small spots. The first type of neurons is mostly located in upper tectal layers, the latter only in deeper layers. Excitatory centre sizes increase with depth, and there is a tendency of smaller receptive fields in the foveal region. The representation of the frontal visual field does not show specializations which could be expected if it were used for fixation of grain during pecking. Our results are in accordance with previous behavioural experiments.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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