The Projection of the Retina, Including the ‘Red Area’, on to the Optic Tectum of the Pigeon

Abstract

The optic tectum of the pigeon has been mapped physiologically, including much of the inferior surface. There are two separate regions of high magnification factor, the projection areas of the fovea and the middle of the red area in the retina, each of which has a correspondingly high density of neurones in the ganglion cell layer.Many avian retinae differ from those of mammals in that they contain two regions of increased ganglion cell density instead of one. In hawks there are two foveae: one central looking laterally, and the other in the temporal retina looking forwards [Rochon-Duvigneaud, 1943]. In pigeons there is only one true fovea for each eye, but there is a second area in the superior temporal retina, known as the 'red area', whose ganglion cell density almost equals that of the fovea [Whitteridge, 1965;Galifret, 1968;Binggeli and Paule, 1969], and whose synaptic organization is particularly complex [Yazulla, 1974]. The red area receives the image of the visual field in the region of the beak, for all stationary positions of the head, since the static component of ocular counterrotation following head movements is less than 10% [Benjamins and Huizinga, 1927].These facts suggest that the red area has a specialized function, and Nye's [1973] behavioural experiments suggest that it is superior to even the fovea for analyzing image structure, motion, colour and pattern. It is therefore of interest to locate the red area's projection site on the tectum and to determine its magnification factor. Previous electrophysiological maps [e.g. Hamdi and Whitteridge, 1954;Bilge, 1971] are inadequate for the lower-tectal surface where the red area projects, and the map of McGill, Powell and Cowan [1966], based on fibre degeneration following retinal lesions, is unavoidably coarse. We have therefore mapped the tectum in some detail, including much of the lower surface, and have compared the magnification factor for the red area with that for other retinal regions. METHODS Retinal histologyThe eyes were fixed in Kolmer's fluid [Walls, 1938], stored in terpineol for several weeks, embedded in paraffin wax, cut in horizontal or vertical planes, and stained with cresyl violet. Of four eyes taken, three provided acceptable sections 10 ,um thick. On the assumption that 351.. ICA

A centrifugally controlled circuit in the avian retina and its possible role in visual attention switching

“…Retinal ganglion cells project [directly and/or indirectly (Uchiyama & Watanabe, 1985;Woodson et al, 1991)] onto the neurons of origin of the tecto-ION projection, which in turn project onto the isthmo-optic neurons. At each of these stages, topography is respected approximately and the predominant influence is excitatory (Clarke & Whitteridge, 1976;Uchiyama, 1989). The ION neurons innervate amacrine cells in the ventral retina, their most powerful input being via pericellular nests onto association amacrines that we identify as type II proprioretinal cells (Catsicas et al, 1987a).…”

Attentional Capture? Synchronized Feedback Signals from the Isthmi Boost Retinal Signals to Higher Visual Areas

“…Because SLu neurons have RFs twice as large as Ipc neurons (45 Ϯ 15 deg in diameter vs 20 Ϯ 3 deg), feedback from the SLu would affect a larger tectal area than feedback from the Ipc. Thus, a 1 deg visual spot activating a tectal area of 0.1 mm in diameter (Clarke and Whitteridge, 1976) would elicit simultaneous feedback from the SLu and Ipc encompassing a tectal area of ϳ4.5 and 2 mm in diameter, respectively, both larger than the retinal input in the superficial layers. For visual stimuli moving in one direction, feedback from the Ipc and SLu may exert a priming effect on neurons ahead of the visual wave-front propagating across the tectal surface, e.g., by targeting the shepherd-crook neurons projecting back to the isthmi or the widely distributed bottlebrush endings of tectal ganglion cells.…”

Regional Variation in Receptive Field Properties of Tectal Neurons in Pigeons

“…Neuroanatomical [Hamdi and Whitteridge, 1954;McGill et al, 1966;Hard, 1972;Hunt and Webster, 1975;Remy and Güntürkün, 1991] and electrophysiological [Hamdi and Whitteridge, 1954;Bilge, 1971;Clarke and Whitteridge, 1976] studies have shown that the avian retina primarily projects onto the contralateral tectum in a topographical manner. The dorsal and ventral retina project onto the ventral and dorsal tectum, respectively; and the horizontal meridian of the retina is represented in the lateral tectum.…”

“…Anatomical and electrophysiological mappings [Bilge, 1971;Clarke and Whitteridge, 1976;Remy and Güntürkün, 1991;Karten et al, 1997] have indicated that the ventral tectum is the projection region of the dorsal retina with the red field, which corresponds to the pecking field in pigeons [Goodale, 1983;Nalbach et al, 1990]. The isthmo-optic nucleus, a major component of the centrifugal system in birds, mainly receives input from the ventral tectum [Woodson et al, 1995].…”