An electrophysiological study of the hyperstriatal visual projection area in the young chicken.

Denton, Christopher John (1979). An electrophysiological study of the hyperstriatal visual projection area in the young chicken. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000fc7d

Abstract

The structural organisation of avian visual pathways is discussed, and particular reference is made to the retino- thalamo-hyperstriatal projection.

The appearance of the young (1-2 week old) chicken forebrain in Nissl-stained transverse sections is discussed, and an interpretation of the structure and nomenclature of the hyperstriatal complex is presented and compared with the interpretations found in the literature.

An analysis is then presented of field and single unit potentials recorded from the hyperstriatal complex of the 1-2 week old chicken following electrical stimulation of the contralateral and ipsilateral retina and optic papilla. The retino-hyperstriatal projection was found to be topographically organised - thus, the inferior retina was found to project to the posterior regions of the Wulst, and the superior retina to anterior regions of the Wulst.

A complex dorsoventral lamination of visual inputs to the hyperstriatum was revealed. Stimulation of the contralateral anterior retina resulted in early field potentials (mean peak latency, MPL: 14.3+0.7 mS) located in the hyper striatum intercalatus accessorium (IHA), followed by later activity spreading throughout superficial regions of the hyperstriatum accessorium (HA) (MPL: 18.5 + 1.6mS). Similarly, stimulation of the contralateral posterior retina resulted in early potentials (MPL: 14.9 + 1.6mS) in IHA, and late potentials (MPL: 17.2 + 0.9mS) spreading throughout deep regions of HA. It was concluded that IHA was the main visual thalamo-receptive lamina within the hyperstriatal complex.

Stimulation of the ipsilateral optic papilla resulted in a single field potential response (MPL: 21.8 + 3.0mS), located in ventral HA, overlapping ventral areas of the contralaterally responsive region of HA.

The responses of 220 single cells recorded from the hyperstriatum following electrical stimulation of the contralateral and ipsilateral optic papilla were analysed. 123 (56%) of these cells responded to the stimulation. Within the responsive sample, four classes of cell were identified: 85% responded exclusively to contralateral stimulation; 3% responded exclusively to ipsilateral stimulation; 8% responded to both contralateral and ipsilateral stimulation with different latencies (independent binocular); and 4% responded to both contralateral and ipsilateral stimulation with identical latencies (coincident binocular). The single cell responses showed excellent spatiotemporal correlation with the evoked field potentials.

Comparison of these results with those obtained by other workers from the owl and pigeon indicated some similarities between the organisation of the thalamofugal pathway in chicken and owl, but also that at present, no single species should be assumed to be typical of the avian class.

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