1,167 research outputs found
Development of flash evoked responses in the ectostriatum of the zebra finch: an evoked potential and current-source-density analysis
No full textEngelage J, Bischof H-J. Development of flash evoked responses in the ectostriatum of the zebra finch: an evoked potential and current-source-density analysis. Visual Neuroscience. 1990;5(03):241-248
Visual wulst influences on flash evoked responses in the ectostriatum of the zebra finch
No full textEngelage J, Bischof H-J. Visual wulst influences on flash evoked responses in the ectostriatum of the zebra finch. Brain Research. 1994;652(1):17-27.Anatomical data suggest that visual information from the thalamofugal pathway contributes to visual processing in the tectofugal pathway. We addressed the question of the functionality of anatomically described connections to the visual system of a laterally eyed bird, the zebra finch. The study shows the contribution of visual wulst efferents to visual processing in the ectostriatum by recordings of visually evoked slow field potentials. Suppression of visual wulst activity resulted in a selective reduction of distinct potential components in contralaterally evoked slow field potentials. A clear reduction was observed in the maximum amplitude of short latency components in the negative wave. Long latency components of the negative wave and the entire positive wave of the contralaterally flash evoked potentials were almost abolished. Ipsilateral visual evoked potentials (VEPs) were not significantly affected. Cooling and spreading depression of the optic tectum resulted in a uniform amplitude reduction of the negative wave. The positive wave was almost abolished. Ipsilateral VEPs disappeared completely during suppression of optic tectum activity. The results showed that the visual wulst has a significant, most likely facilitatory, influence on the processing of contralateral visual information in the ectostriatum. Ipsilateral stimulus processing was partly independent from visual wulst activity. A model for thalamo- and tectofugal connectivity in the ectostriatum is suggested
The organization of the tectofugal pathway in birds: a comparative review
No full textEngelage J, Bischof H-J. The organization of the tectofugal pathway in birds: a comparative review. In: Zeigler HP, ed. Vision, brain, and behavior in birds. Cambridge, Mass.: MIT Press; 1993: 137-158
Development and Plasticity of the Tectofugal Visual Pathway in the Zebra Finch
No full textBischof H-J, Herrmann K, Engelage J. Development and Plasticity of the Tectofugal Visual Pathway in the Zebra Finch. In: Bagnoli P, ed. The changing visual system: maturation and aging in the central nervous system. NATO ASI Series : Series A. Vol 222. New York: Plenum; 1991: 199-208
Flash evoked potentials in the ectostriatum of the zebra finch: a current source density analysis
No full textEngelage J, Bischof H-J. Flash evoked potentials in the ectostriatum of the zebra finch: a current source density analysis. Experimental Brain Research. 1989;74(3):563-572.Recent research has demonstrated that ipsilaterally visually evoked potentials (VEPs) can be measured within the ectostriatum, the telencephalic target area of the tectofugal visual pathway in birds. In this paper we systematically measured contra- and ipsilateral VEPs within the ectostriatal complex to obtain more detailed information on the processing of contra- and ipsilateral stimuli. The similarity of neighbouring VEPs at equal depth and a comparison of a one dimensional and a three dimensional analysis of current source-densities (CSDs) for identical coordinates suggested that a one dimensional current source-density analysis might be applicable. The one dimensional current source-density analysis demonstrated largely corresponding patterns in the sink-source sequences of the current source-density depth profiles for the contra- and ipsilateral stimulus responses. The occurence of a large sink in the centre of the ectostriatal core, together with the results of multiunit recordings, shows that the ectostriatal core is the location of the generators for both the contra- and the ipsilaterally evoked responses. The occurrence of macroscopic sinks and sources and the fact that VEPs can be recorded from the ectostriatum shows that there is a higher degree of order in the ectostriatum than has been previously demonstrated by anatomical methods. The time coincidence between the maximum spike rate of multiunit responses, the negative peak of the evoked potential, and the large central sink demonstrates that the influence of ipsi- as well as of contralateral stimuli is predominantly excitatory
Single cell responses in the ectostriatum of the zebra finch
No full textEngelage J, Bischof H-J. Single cell responses in the ectostriatum of the zebra finch. JOURNAL OF COMPARATIVE PHYSIOLOGY A-NEUROETHOLOGY SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY. 1996;179(6):785-795.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
Flash evoked responses in a song control nucleus of the zebra finch (Taeniopygia guttata castanotis)
No full textBischof H-J, Engelage J. Flash evoked responses in a song control nucleus of the zebra finch (Taeniopygia guttata castanotis). Brain Research. 1985;326(2):370-374.The song of the zebra finch is facilitated and altered by the presence of a female. Thus, visual information should affect the song system of the bird. Visually evoked potentials can be recorded from n. hyperstriatum ventrale pars caudale (HVc). The long latency of this potential and its variability indicate several processing steps between primary sensory areas of the telencephalon and HVC. Within HVc, under these experimental conditions no interaction between acoustic and visual input could be demonstrated. However, at the dorsal border and within the shelf below HVc, visual information seems to enhance acoustically evoked potentials
Single cell responses from the optic tectum of the zebra finch (Taeniopygia guttata castanotis Gould)
No full textSchmidt A, Engelage J, Bischof H-J. Single cell responses from the optic tectum of the zebra finch (Taeniopygia guttata castanotis Gould). JOURNAL OF COMPARATIVE PHYSIOLOGY A-SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY. 1999;185(1):69-79.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 degrees. The representation of the contralateral hemifield extends to the ipsilateral side by 15 degrees. Most neurons have receptive fields with excitatory centres of different shapes and inhibitory surround. A hew 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
Visual system alterations in white zebra finches
No full textBredenkotter M, Engelage J, Bischof H-J. Visual system alterations in white zebra finches. BRAIN BEHAVIOR AND EVOLUTION. 1996;47(1):23-32.Visual system anomalies in albino mammals are generally seen to be caused by a lack of retinal pigment and misrouting of retinofugal optic fibers. This study shows that the central visual system of white zebra finches is physiologically different from normally colored (wild type) birds, although the eye pigmentation and the retinofugal projection appear to be normal. Ipsilaterally evoked potentials in our white birds are enhanced in comparison to wild type birds, whereas in albino mammals the ipsilateral component of visually evoked potentials is reduced. Picrotoxin-induced blockade of inhibitory synapses in the ectostriatum reveals remarkable differences between wild type and white zebra finches. In wild type zebra finches, a significant shift of ipsilateral to contralateral stimulus response ratios is observed. However, there is no detectable shift in the white morph. The data suggest that inhibition of ipsilateral stimulus processing, as observed in wild type zebra finches, is significantly reduced in the white morph. Our results indicate that the effects observed in white zebra finches cannot be explained by the theories that have been developed for albinotic animals. We assume that in white zebra finches a genetic defect, which causes the white plumage, is coupled with the demonstrated deviations of inhibitory mechanisms in the central visual system
Enucleation enhances ipsilateral flash evoked responses in the ectostriatum of the zebra finch (Taeniopygia guttata castanotis Gould)
No full textEngelage J, Bischof H-J. Enucleation enhances ipsilateral flash evoked responses in the ectostriatum of the zebra finch (Taeniopygia guttata castanotis Gould). Experimental Brain Research. 1988;70(1):79-89.The tectofugal pathway in birds has been reported to process primarily information from the contralateral eye. Although this pathway has access to the contralateral hemisphere by various connections, electrophysiological recordings up to now have failed to demonstrate any excitatory influence of visual stimulation in the higher stations of this pathway. This study is the first to demonstrate an excitatory projection from the ipsilateral eye to the telencephalic projection area of the tectofugal pathway by recordings of visually evoked potentials in the ectostriatum. The excitatory projection probably leads from the eye to the contralateral tectum opticum, then recrosses back to the nucleus rotundus of the ipsilateral side where it reaches the ectostriatum. In normal birds, the ipsilateral stimulus responses in the ectostriatum are smaller in amplitude and have a longer latency than responses to contralateral stimuli. In unilaterally enucleated birds, the ipsilateral response is enhanced in the ectostriatum and can be detected in the nucleus rotundus, too. The results suggest that in normal birds the ipsilateral response is inhibited to a high degree by spontaneous activity of the contralateral eye. Possibly, this counterbalanced inhibition provides a mechanism for weighting information from the left and right eye field in order to ensure adequate processing of stimuli
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