Learning in an isolated prothoracic insect ganglion

Abstract

1. 1. The capacity of the isolated prothoracic ganglion to learn was investigated in adult male cockroaches, Periplaneta americana. The head was removed and the posterior connectives of the prothoracic ganglion were severed. Such a ‘miniature’ system was found capable of demonstrating avoidance learning. 2. 2. The avoidance response could be achieved by a number of different leg positions and appeared to be maintained by proprioceptive feedback. The predominant avoidance response involved flexion of the coxal-trochanter joint accompanied by tibial extension. 3. 3. In an additional group of animals the prothoracic ganglion was removed and they were given the same training and testing procedures as those with an isolated prothoracic ganglion. The results showed that long-term generalized excitability changes could occur from the effects of the shock on the peripheral neuromuscular apparatus itself. The response however was quite stereoptyped and showed none of the complexity seen in those with an intact isolated prothoracic ganglion. No P-R difference was obtained.