Visual processing in pigeon nucleus rotundus: Luminance, color, motion, and looming subdivisions

Abstract

The responses of single cells to luminance, color and computer-generated spots, bars, kinematograms, and motion-in-depth stimuli were studied in the nucleus rotundus of pigeons. Systematic electrode penetrations revealed that there are several functionally distinct subdivisions within rotundus where six classes of visual-selective cells cluster. Cells in the dorsal-posterior zone of the nucleus respond selectively to motion in depth (i.e. an expanding or contracting figure in the visual field). Most cells recorded from the dorsal-anterior region responded selectively to the color of the stimulus. The firing rate of the cells in the anterior-central zone, however, is dramatically modulated by changing the level of illumination over the whole visual field. Cells in the ventral subdivision strongly respond to moving occlusion edges and very small moving objects, with either excitatory or inhibitory responses. These results indicate that visual information processing of color, ambient illumination, and motion in depth are segregated into different subdivisions at the level of nucleus rotundus in the avian brain.

A Dissociation of Motion and Spatial-Pattern Vision in the Avian Telencephalon: Implications for the Evolution of “Visual Streams”

“…Wang et al (1993) found that neurons in the posterior nRT are motion sensitive, whereas neurons responsive to color and luminance are found in the anterior nRT. Husband and Shimizu (1999) showed that the caudal Ec receives input from the posterior nRT, and the rostral Ec receives input from the anterior nRT (Benowitz and Karten, 1976;Laverghetta and Shimizu, 2003).…”

“…Four groups of neurons were found: color, luminance, simple motion, and looming (Sun and Frost, 1998). The color and luminance cells were found in the rostral areas of nRT, whereas the motion and looming cells were found in the caudal nRT (Wang et al, 1993).…”

“…Early electrophysiological studies showed that the majority of cells in nRT were motion sensitive (Revzin, 1979). More recently, Wang et al (1993) recorded nRT activity to various types of visual stimuli. Four groups of neurons were found: color, luminance, simple motion, and looming (Sun and Frost, 1998).…”

“…The nRT-Ec projection is topographic: the caudal and rostral Ec receive input from subnuclei in the caudal and rostral nRT, respectively (Benowitz and Karten, 1976;Nixdorf and Bischof, 1982). The physiological organization of nRT (see above) (Wang et al, 1993) suggests that the caudal Ec should be important for visual motion processing, whereas the rostral Ec should be important for spatial-pattern vision and color. We tested this hypothesis by assessing motion and spatialpattern vision in pigeons before and after lesions to the rostral or caudal Ec.…”

Spatial contrast sensitivity of birds

“…In addition, the eagle function (Reymond and Wolfe, 1981) and the kestrel function (Hirsch, 1982) are each comprised of data from a single subject only. This paucity of data is rather surprising considering the substantial literature that exists on the optics, anatomy, physiology, and histochemistry of the eye, the retina, and the central visual system of birds (Karten, 1969;Karten et al, 1973;Shimizu, Cox, and Karten, 1995;Hodos and Erichsen, 1990;Holden, 1980;Bagnoli, 1984;Wang, Jiang, and Frost, 1993), including a number of studies that have been carried out on their visual acuity (Hodos and Leibowitz, 1976;Hodos, et al, 1991a;Gaffney and Hodos, 2003;Güntürkün and Hahmann, 1994;Hahmann and Güntürkün, 1993;Schmid and Wildsoet, 1998;Porciatti, et al, 1991;Hirsch, 1982;Reymond and Wolfe, 1981;Reymond, 1987;Martin and Gordon, 1974;Fite, 1973;Fite and RosenfieldWessels, 1975;Fox, et al, 1976;Dabrowska, 1975;Blough, 1971; Orders combined. Since a great deal of diversity is found in avian visual morphology, specialized for various econiches, it would not be surprising to find avian species that had contrast sensitivities currently considered to be in the mammalian range.…”