Regulation of ipsilateral visual information within the tectofugal visual system in zebra finches

Voss, Joe; Bischof, Hans‐Joachim

doi:10.1007/s00359-003-0430-2

Cited by 19 publications

(12 citation statements)

References 18 publications

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“…1). During integration of bilateral visual input at rotundal level, information from the ipsilateral eye is selectively inhibited by GABAergic fibers from this cluster of nuclei, thereby modulating the shift of attention from one eye to the other [23]. As such an attention shift may play a critical role in modulating functional lateralization, the present study is a first step to investigate if the SP is involved in the mediation of functional asymmetries.…”

Section: Introductionmentioning

confidence: 90%

A morphological study of the nucleus subpretectalis of the pigeon

Freund

Güntürkün

Manns

2008

Brain Research Bulletin

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In pigeons, the tectofugal system is functionally as well as structurally lateralized. So for example the right nucleus rotundus is less modulated by right forebrain influences than the left nucleus rotundus by the left ones. This functional lateralization pattern may depend on a dynamic balance between left and right tectal processing. Apart from inhibitory interactions at tectal level, suppressive influences might directly affect rotundal neurons by GABAergic input from a cluster of nuclei, the bed nuclei of the tecto-thalamic tract. A major afferent of these nuclei is the side branch of the tectorotundal projection which is of bilateral origin and which is involved in the regulation of ipsilateral as well as bilateral visual processing. Hence, an important role of the bed nuclei could be the interhemispheric communication and in turn the mediation of functional asymmetries. In a first step to unravel asymmetric influences of these nuclei, the present study investigated if the largest of the bed nuclei, the nucleus subpretectalis displays morphological asymmetries in the pigeon. We found that the nucleus subpretectalis in fact exhibits asymmetric cell sizes with larger cell bodies on the left side. This asymmetrical pattern was not present in dark-incubated animals indicating that cell size asymmetries within nucleus subpretectalis are induced by asymmetric photic stimulation during embryonic development.

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Section: Introductionmentioning

confidence: 90%

A morphological study of the nucleus subpretectalis of the pigeon

Freund

Güntürkün

Manns

2008

Brain Research Bulletin

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“…The other involves a cluster of GABAergic structures collectively called the bed nuclei of the tectothalamic tract. These nuclei receive a side branch of the tectorotundal projection from both halfbrains (Theiss et al, 2003) and are involved in the regulation of ipsilateral and bilateral visual input in Rt (Voss and Bischof, 2003).…”

Section: Top-down Influences Onto the Tectofugal Systemmentioning

confidence: 99%

Asymmetrical Modes of Visual Bottom-Up and Top-Down Integration in the Thalamic Nucleus Rotundus of Pigeons

Folta¹,

Diekamp²,

Güntürkün³

2004

J. Neurosci.

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The aim of this study was to separate bottom-up and top-down influences within cerebral asymmetries. This was studied in the lateralized visual system of pigeons by recording from single units of the left and right diencephalic nucleus rotundus of the tectofugal pathway while visually stimulating the ipsilateral and/or contralateral eye. Analyses of response latencies revealed rotundal neurons with short and/or late response components. Cells with short latencies very likely represent bottom-up neurons participating in the ascending retinotectorotundal system. Because lidocaine injections into the visual Wulst produced a significant reduction of late response components only, neurons with long latencies were probably activated via a top-down telencephalotectorotundal system. The distribution and response characteristics of bottom-up and top-down neurons provided insight into several asymmetries of ascending and descending pathways. Asymmetries of the ascending retinotectorotundal system (bottom-up) were characterized by longer periods of tonic activation in the left and shorter response latencies in the right rotundus. Left-right differences in these responses probably facilitate faster access to visual input to the right hemisphere and a prolonged processing of this input in the left. The descending telencephalotectorotundal system (top-down) revealed a completely different lateralized organization. This system was characterized by long latency responses that exclusively derived from the left hemisphere, regardless of whether recordings took place in the left or the right rotundus. We assume that asymmetrical modes of visual processing within both hemispheres of the ascending tectofugal system are ultimately directed to left hemispheric forebrain mechanisms that subsequently generate executive control over sensory and motor structures.

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“…Inhibition mechanisms for blocking or at least suppressing information from the unattended fovea have been demonstrated within the tectofugal visual system (Engelage and Bischof, 1988;Voss and Bischof, 2003), which is the main visual pathway in laterally eyed birds (Hellmann and Güntürkün, 2001) and can be seen as homologue of the extrageniculocortical pathway in mammals (Shimizu and Karten, 1990). In all birds, information from the eye is conveyed by the optic nerve to the contralateral hemisphere, at first glance suggesting that the eye information is completely processed there (Cowan et al, 1961).…”

Section: Introductionmentioning

confidence: 99%

Eye movements of laterally eyed birds are not independent

Voss

Bischof

2009

Journal of Experimental Biology

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SUMMARYMost birds have laterally placed eyes with two largely separated visual fields. According to studies in pigeons laterally eyed birds move their eyes independently in most situations, eye coordination just occurred during converging saccades towards frontal stimuli. Here we demonstrate for the first time that laterally eyed zebra finches show coordinated eye movements, regarding direction and amplitude. Spontaneous and visually elicited movements of the two eyes were recorded simultaneously, using a newly developed eye tracking system. We found that, if one eye moves in a certain direction, the other eye simultaneously performs a counter-movement in the opposite direction. Based on these data we developed a hypothesis of how laterally eyed birds cope with the situation in which the left and right eye simultaneously obtain images with different content. We suggest that the counter-movements maintain the spatial relationship of the two visual fields. 'Oculospatial constancy', as we call it, facilitates the combination of the left and right visual percept on the level of peripheral or unattended viewing, and the localization of appearing stimuli within the whole visual field. As soon as two visual stimuli simultaneously appear in the left and right visual field, the birds decide on one stimulus and direct the fovea of the appropriate eye towards it for high resolution analysis, the other eye simultaneously performing a counter-saccade. This leads to the assumption that, in contrast to simultaneous peripheral perception with two eyes, the processing of foveal information is possible only for one eye at one time.

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Regulation of ipsilateral visual information within the tectofugal visual system in zebra finches

Cited by 19 publications

References 18 publications

A morphological study of the nucleus subpretectalis of the pigeon

A morphological study of the nucleus subpretectalis of the pigeon

Asymmetrical Modes of Visual Bottom-Up and Top-Down Integration in the Thalamic Nucleus Rotundus of Pigeons

Eye movements of laterally eyed birds are not independent

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