Critical period of memory enhancement during taste avoidance conditioning in Lymnaea stagnalis

PLoS One. 2013 Oct 3;8(10):e75276. doi: 10.1371/journal.pone.0075276. eCollection 2013.


The present study investigated the optimal training procedure leading to long-lasting taste avoidance behavior in Lymnaea. A training procedure comprising 5 repeated pairings of a conditional stimulus (CS, sucrose), with an unconditional stimulus (US, a tactile stimulation to the animal's head), over a 4-day period resulted in an enhanced memory formation than 10 CS-US repeated pairings over a 2-day period or 20 CS-US repeated pairings on a single day. Backward conditioning (US-CS) pairings did not result in conditioning. Thus, this taste avoidance conditioning was CS-US pairing specific. Food avoidance behavior was not observed following training, however, if snails were immediately subjected to a cold-block (4°C for 10 min). It was critical that the cold-block be applied within 10 min to block long-term memory (LTM) formation. Further, exposure to the cold-block 180 min after training also blocked both STM and LTM formation. The effects of the cold-block on subsequent learning and memory formation were also examined. We found no long lasting effects of the cold-block on subsequent memory formation. If protein kinase C was activated before the conditioning paradigm, snails could still acquire STM despite exposure to the cold-block.

MeSH terms

  • Animals
  • Avoidance Learning / physiology*
  • Conditioning, Psychological / physiology*
  • Lymnaea*
  • Memory / physiology*
  • Protein Kinase C / metabolism
  • Taste*


  • Protein Kinase C

Grant support

The authors have no support or funding to report.