A true neuronal consensual pupillary reflex in chicks.
The existence of a true neuronal consensual pupillary reflex (CPR) in birds has long been debated. In this century Noll (Noll, A. (1915). Archiv für Physiologie (Leipzig), 350-372.) claimed to observe a neuronal CPR in a pigeon, but this was contradicted by Levine (Levine, J. (1955). Science, 122, 699.), who observed a direct transillumination effect (Durchleuchtungs-effekt) due to the retinas of the two eyes of the pigeon being in close apposition. To determine if a neuronal CPR exists, we transected the optic nerves of 28 chicks and observed and videotaped the direct and indirect pupillary responses. Twenty-one of the chicks exhibited no direct response in the operated eye but did exhibit an indirect pupillary response. The non-operated eye showed a direct but no indirect response. These results conclusively demonstrate for the first time that a true neuronal CPR does exist in chickens.
Li
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Section of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA. TL24@Cornell.edu
Howland
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D000818:Animals; D002645:Chickens / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D009900:Optic Nerve / Q000601:surgery; D010775:Photic Stimulation; D012025:Reflex, Pupillary / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology