The spectral sensitivity of the pigeon (Columba livia)

Abstract

The pigeon's retinal function has been studied by electroretinography. The duplex nature and the cone-predominancy of the retina have been demonstrated by the ERG waveform, by the effects of stimulus intensity, by the position of the retina stimulated, and by darkadaptation.The scotopic spectral sensitivity was determined with small b-waves evoked by a stimulus inclined at 30° to the optical axis in fully dark-adapted eyes. The scotopic spectral sensitivity curve has its maximum at 502 mμ and is in close agreement with the absorption spectrum of the pigeon's rod pigment.The sensitivity curves obtained from the ERG evoked by the light directed along the optical axis of the retina did not fit the rod pigment curve. Furthermore, a change in the spectral distribution of the sensitivity from the scotopic to photopic (the Purkinje shift) was observed when the response criterion value for determining the sensitivity was changed from a scotopic b-wave range to photopic b-wave range.The photopic sensitivity was determined by 40 c/s flicker ERG elicited by axial stimuli. The sensitivity curve was in fair agreement with the absorption spectrum of the pigeon's cone pigment (λmax = 544 mμ).The effect of the oil droplets and the discrepancies between the photopic sensitivity curve (λmax = 547 mμ) and the photopic dominator curve (λmax = 580 mμ) otbained by the earlier workers are discussed.Another spectral sensitivity curve having its maximum at 605 mμ was obtained after selective adaptation to 547 mμ light. This suggests the possibility of a third pigment in the pigeon retina.Two narrow-bandwidth spectral sensitivity curves that were in good agreement with the green and red modulators reported in the ganglion cell spike of the pigeon by Donner were found. One, which corresponded to Donner's green modulator, was obtained with high amplitude b-waves evoked axially. The other, which corresponded to Donner's red modulator, was obtained with the ERG off-response. This indicates that the ERG of the pigeon shares the spectral properties of the ganglion cells.