Are eyeblink responses to tone in the decerebrate, decerebellate rabbit conditioned responses?
Bloedel and associates recently claimed to have established conditioned eyeblink responses in the acute decerebrate, decerebellate rabbit. Their training procedure was extreme massed practice (mean intertrial interval of 9 s) and they used an idiosyncratic definition of the conditioned response (10% or more of the unconditioned response amplitude). They did not measure or control the excitability of their preparations and did not run any separate control groups for alpha responses, alpha conditioning or pseudoconditioning. Using normal animals we compared their training procedure with procedures standard in the field and analyzed the consequences of their scoring procedure. Our group trained at a 30-s intertrial interval (ITI) showed clear learning in the training session. In marked contrast, 3 groups trained at a 9-s ITI developed no conditioned responses. We also found that the method of scoring used by Bloedel and associates counts many spontaneous responses as conditioned responses (CRs) if unconditioned response (UR) amplitudes are low, excludes genuine CRs if UR amplitudes are high and does not control for the occurrence of spontaneous responses. It must therefore be concluded that the eyeblink responses to tone reported by Bloedel and associates to occur in the decerebrate, decerebellate rabbit are not associative CRs as they develop in the normal animal.
Nordholm
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Neurosciences Program, University of Southern California, Los Angeles 90089-2520.
Lavond
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DG
Thompson
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D000818:Animals; D001767:Blinking / Q000502:physiology*; D002531:Cerebellum / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D003655:Decerebrate State; D008297:Male; D009129:Muscle Tonus / Q000502:physiology*; D009541:Nictitating Membrane / Q000502:physiology; D011817:Rabbits; D012149:Restraint, Physical