Neuronal responses ofHelix pomatia to tactile stimulation

Conclusion

• 1. Convergence of effects from different parts of the skin and reciprocal relationships between the caudal and cranial parts on neurons of the subesophageal ganglion in the snail have been found.

• 2. Identical patterns of excitation and inhibition have been note in adjacent neurons.

• 3. Two types of neurons are distinguished: those possessing spontaneous activity and responding by a change in frequency of discharge and those not possessing spontaneous activity and responding by a group of action potentials.

• 4. Weakening or disappearance of responses in observed in both types of neurons on repetition of tactile stimulation at the same point, and reappearnce of response is observed with a change in locus of stimulation.

• 5. Three hypotheses concering mechanisms of “habituation” are compared: adaptation of tactile receptors, desensitization of the synaptic membrane of the central neuron, and potentiation of inhibitory synapses of interneurons in the nerve net, leading to parallel inhibition. It is concluded that habituation is based on a central synaptic organization, similar to that of extinction of the orienting reflex.