Contraction of neuronal branching volume: An anatomic correlate of Pavlovian conditioning

D. L. Alkon, H. Ikeno, J. Dworkin, D. L. Mcphie, J. L. Olds, I. Lederhendler, L. Matzel, B. G. Schreurs, A. Kuzirian, C. Colein, E. Yamoah

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Associative memory of the mollusc Hermissenda crassicornis, previously correlated with changes of specific K+ currents, protein phosphorylation, and increased synthesis of mRNA and specific proteins, is here shown to be accompanied by macroscopic alteration in the structure of a single identified neuron, the medial type B photoreceptor cell. Four to five days after training, terminal arborizations of B cells iontophoretically injected with Ni2+ ions and then treated with rubeanic acid were measured with charge-coupled device (CCD)-digitized pseudocolor images of optical sections under "blind" conditions. Boundary volumes enclosing medial-type B-cell arborizations from classically conditioned animals were unequivocally reduced compared with volumes for naive animals or those trained with unpaired stimuli. Branch volume magnitude was correlated with input resistance of the medial type B-cell soma. Such associative learning-induced structural changes may share function with "synapse elimination" described in developmental contexts.

Original languageEnglish (US)
Pages (from-to)1611-1614
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number4
StatePublished - 1990
Externally publishedYes


  • Associative memory
  • Hermissenda
  • Learning
  • Morphologic correlates

ASJC Scopus subject areas

  • Genetics
  • General


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