Verification of skeletal activity in tibial nerve recordings: a reply to Roberts (1991).

In Dworkin and Dworkin (1990), we described classically conditioned tibial nerve responses that were uncorrelated with vasomotor responses in the same limb. We pointed out that this finding conflicted with the persisting idea that skeletal and autonomic responses are permanently locked into fixed action patterns that can not be reorganized by learning (Cohen & Obrist, 1975). Roberts (1991) has doubted our interpretation. In this reply, we rebut his arguments and also describe new pharmacological and other recent data showing unambiguously that the nerve activity we measured was not of postganglionic sympathetic origin. We conclude that the nerve activity was most probably due to motoneurons and reiterate that the results of our experiment specifically failed to support a general assertion of obligatory central coupling between skeletal and autonomic mechanisms.