Blocking and the detection of odor components in blends

Recent studies of olfactory blocking have revealed that binary odorant mixt ures are not always processed as though they give rise to mixture-unique co nfigural properties. When animals are conditioned to one odorant (A) and th en conditioned to a mixture of that odorant with a second (X), the ability to learn or express the association of X with reinforcement appears to be r educed relative to animals that were not preconditioned to A. A recent mode l of odor-based response patterns in the insect antennal lobe predicts that the strength of the blocking effect will be related to the perceptual simi larity between the two odorants, i.e. greater similarity should increase th e blocking effect. Here, we test that model in the honeybee Apis mellifera by first establishing a generalization matrix for three odorants and then t esting for blocking between all possible combinations of them. We confirm e arlier findings demonstrating the occurrence of the blocking effect in olfa ctory learning of compound stimuli. We show that the occurrence and the str ength of the blocking effect depend on the odorants used in the experiment. In addition, we find very good agreement between our results and the model , and less agreement between our results and an alternative model recently proposed to explain the effect.