Olfactory perception and bulbar electrical activity in several avian species

Abstract

Our earlier work on the olfactory responses of pigeons has been extended to six other species of birds, viz., canary ( Serinus canaris), bobwhite quail ( Colinus virginianus virginianus), mallard duck ( Anas platyrhynchos), turkey vulture ( Cathartes aura), raven ( Corvus corax), and blackvented shearwater ( Puffinus puffinus opisthomelas). Heart rate and respiration were monitored in all of these forms during presentation of olfactory stimuli of pure air or bright light. In all but raven, canary and quail, the electrical activity of the olfactory bulb was also recorded through permanently implanted electrodes. Amyl acetate, pyridine, and trimethylpentane were used as olfactory stimuli with all species; the vulture and shearwaters were also tested with natural stimuli of decayed meat and ground fish, respectively. Olfactory bulb electrical activity showed characteristic vertebrate components such as inspiration-linked intrinsic spindles in the frequency range between 20 and 40 Hz, a large ac spike at the onset of odor stimulation that probably corresponds to the electro-bulbo-olfactogram of dc recording, and desynchronization as a result of visual stimulation during a period of relaxation. No consistent species differences were seen. Responses to amyl acetate and trimethylpentane were characteristically different across species. All forms but the raven showed significant somatic responses to some, but not all, of the odorous stimuli presented. Surprisingly, the raven failed to show such responses even to the visual stimulus. The somatic responses were more reliable in species with larger olfactory bulbs, such as the ducks and shear-waters, but were found in birds with extremely small bulbs as well. It seems fair to say that perceptual capacity for olfactory stimuli is likely to exist in all avian species but may differ widely in amount and significance.