Effect of tectotomy and decerebration on spontaneous and elicited behavior of tadpoles and juvenile frogs.

The performance of tadpoles and juvenile frogs on a battery of behavioral tests was compared before and after tectotomy, removal of the telencephalon (decerebration), tectotomy in conjunction with decerebration, or before and after a sham operation. Posture, righting, and vestibular responses were not altered by any of the lesions at either stage of development, and gross motor abilities were not impaired. Cutaneous reflex thresholds of tadpoles were lower than those of juveniles prior to surgery, but removal of the tectum or the telencephalon, or of both, reduced the thresholds of juveniles to near-larval levels. All of the lesions abolished characteristic defensive responses of juveniles (freezing) and resulted in hyperreactivity to a wide variety of stimuli. Tectotomy and decerebration of larvae each resulted in a 50% reduction in spontaneous locomotion and, in combination, virtually eliminated spontaneous locomotion. None of the lesions had any effect on the level of spontaneous locomotion of juveniles, but activity elicited by the novelty of the testing environment was eliminated in decerebrate subjects. Visual and vestibular nystagmus consisted of eye movements in tadpoles and of head movements in juveniles. Neither nystagmus nor optokinetic locomotion was affected by any of the lesions at either stage.