Associative learning in Aplysia: Evidence for conditioned fear in an invertebrate

Edgar T. Walters, Thomas J. Carew, Eric R. Kandel

Research output: Contribution to journalArticlepeer-review


Aversive classical conditioning of Aplysia californica, a gastropod mollusk suited for neurobiological study, produces a learned reaction to the chemosensory conditioned stimulus that is expressed as a marked facilitation of four defensive responses: two graded reflexes (head and siphon withdrawal), an all-or-none fixed act (inking), and a complex fixed action pattern (escape locomotion). In addition, the conditioned stimulus produces a concomitant depression of at least one appetitive response, feeding. These extensive and selective actions of the conditioned stimulus in Aplysia resemble the actions of conditioned fear stimuli in higher mammals and suggest that the functional equivalent of fear occurs in invertebrates and thus may be an adaptive mechanism that is widespread in the animal kingdom.

Original languageEnglish (US)
Pages (from-to)504-506
Number of pages3
Issue number4481
StatePublished - 1981

ASJC Scopus subject areas

  • General


Dive into the research topics of 'Associative learning in Aplysia: Evidence for conditioned fear in an invertebrate'. Together they form a unique fingerprint.

Cite this