Operant Conditioning in Lymnaea: Evidence for Intermediate- and Long-term Memory

Abstract

Aerial respiration of the pond snail, Lymnaea stagnalis, can be operantly conditioned; however, the parameters necessary to produce long-term (LTM) or intermediate term memory (ITM) have not previously been investigated. We conducted training using procedures that varied in the duration of the training session, the number of training sessions per day or the amount of time between subsequent training sessions (SI). We found that by varying the duration and frequency of the training session learning could be differentially produced. Furthermore, the ability to form LTM was dependent not only on the duration of the training session was also the interval between training sessions, the SI. Thus it was possible to produce ITM, which persists for up to 3 hr, and not form LTM, which persists at least 18 hr. Learning, ITM, and LTM can be differentially produced by altering the SI, the duration of the training session, or the number of training sessions per day. These findings may allow us to begin to elucidate the underlying neural mechanisms of learning, ITM, and LTM.

Context Learning and the Effect of Context on Memory Retrieval in Lymnaea

“…Changes in protein synthesis that occur locally and extrasomally (Martin et al 1997;Spencer et al 2000) are hypothesized to underlie this form of memory. Whether a change in context will also affect the ability to retrieve ITM is now being studied using a procedure that only produces ITM (Lukowiak et al 2000a). These experiments and results described here extend the usefulness of operant conditioning of aerial respiration in Lymnaea as a model system in which to directly study how learning and the different forms of memory are mediated at the neuronal level.…”

“…Thus, transcriptional blockers applied just after training prevent the formation of LTM but not intermediate-term memory (ITM). ITM, which persists for only 2-3 h in Lymnaea (Lukowiak et al 2000a), is also dependent on new protein synthesis but not altered gene activity. Thus, using a translational blocker, Scheibenstock and Lukowiak (2000) showed that ITM could be blocked.…”

“…Our previous work showed that the changes observed in aerial respiratory behavior following training are an example of associative learning (Lukowiak et al , 1998(Lukowiak et al , 2000a. However, we have not previously examined the effect of stress, attention, or food availability on the ability of Lymnaea to learn, consolidate the memory, and retrieve the memory.…”

“…This was accomplished by applying a tactile stimulus to the pneumostome on each attempted pneumostome opening during a 30-m period. We then waited 24 h. Based on previous data (Lukowiak et al 2000a), no learning or LTM is produced by this procedure. We then applied a poke to the pneumostome area whenever the animal yoked to the pneumostome attempted to open its.…”

Cognition in Invertebrates

“…Aversive operant conditioning of Lymnaea's aerial respiratory behavior involves stimulating the animal's pneumostome when it surfaces and attempts to breathe (Lukowiak et al, 1996(Lukowiak et al, , 1998(Lukowiak et al, , 2000Lukowiak and Syed, 1999;Spencer et al, 1999;Haney and Lukowiak, 2001;McComb et al, 2002McComb et al, , 2003Sangha et al, 2002Sangha et al, , 2003Scheibenstock et al, 2002;Spencer et al, 2002). The stimulation is aversive, which leads to the animal closing the pneumostome and learning as training progresses to reduce its attempts to open the pneumostome.…”