| Popis: |
Birds offer a number of important advantages for the study of life-span development of the visual system. Their vision is excellent (Hodos, et al., 1985; Wright, 1972; Blough, 1956) and their life span often is considerably shorter than that of humans (Altman and Ditman, 1974). They also are relatively inexpensive to obtain and maintain, especially domesticated species such as pigeons, canaries, chickens, budgerigars and quail from which individuals at nearly all stages of the life span can frequently be obtained. In the article that follows we shall describe a series of anatomical, behavioral and electrophysiological studies we have carried out on pigeons (Columba livia) and Japanese quail (Coturnix coturnix japonica). The behavioral studies consisted of the measurement of visual acuity with operantconditioning techniques as a function of age. The electrophysiological studies evaluated the retina’s contribution to life-span changes in acuity by means of the flash electroretinogram and the pattern electroretinogram. The anatomical studies investigated life-span changes in cellular components of the retina in birds of known visual acuity. |
