Potentiation of phototactic suppression in Hermissenda by a chemosensory stimulus during compound conditioning.

Modifications of Hermissenda's phototactic behavior by compound pairings of light, scallop extract, and rotation were assessed. In general, the scallop extract potentiated phototactic suppression. Potentiation was dependent on (a) conjunctive presentations of scallop and light, (b) number of conditioning trials, and (c) scallop extract concentration. In related experiments, no second-order conditioning or sensory preconditioning of phototactic suppression was observed, indicating that within-compound associations did not contribute appreciably to potentiation. These results represent the first detailed analysis of compound conditioning in a mollusk using discrete presentations of well-characterized conditioned stimuli from distinct sensory modalities.