Context Extinction and Associative Learning in Lymnaea (original) (raw)

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

Learning & Memory, 2000

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.

Neural changes after operant conditioning of the aerial respiratory behavior in Lymnaea stagnalis

The Journal of neuroscience : the official journal of the Society for Neuroscience, 1999

In this study, we demonstrate neural changes that occurred during operant conditioning of the aerial respiratory behavior of Lymnaea stagnalis. Aerial respiration in Lymnaea occurs at the water interface and is achieved by opening and closing movements of its respiratory orifice, the pneumostome. This behavior is controlled by a central pattern generator (CPG), the neurons of which, as well as the motoneurons innervating the pneumostome, have previously been identified and their synaptic connections well characterized. The respiratory behavior was operantly conditioned by applying a mechanical stimulus to the open pneumostome whenever the animal attempted to breathe. This negative reinforcement to the open pneumostome resulted in its immediate closure and a significant reduction in the overall respiratory activity. Electrophysiological recordings from the isolated CNSs after operant conditioning showed that the spontaneous patterned respiratory activity of the CPG neurons was signif...

Operant conditioning of aerial respiratory behaviour in Lymnaea stagnalis

Journal of Experimental Biology

In this study, we operantly conditioned the aerial respiratory behaviour of the freshwater snail Lymnaea stagnalis. Aerial respiration in Lymnaea stagnalis is accomplished by the spontaneous opening and closing of its respiratory orifice, the pneumostome, at the water surface. Weak tactile stimulation of the pneumostome area, when the pneumostome is open, evoked only the pneumostome closure response, which is one aspect of the escape-withdrawal reflex. Pneumostome stimulation resulted in its closure and the termination of aerial respiratory activity. A contingent tactile stimulation paradigm was used to operantly condition the animals. Stimulation of the pneumostome whenever the animal attempted to breathe resulted in significantly fewer attempts to open the pneumostome as training progressed. The latency of the first breath (subsequent to stimulation), the number of breaths and the total breathing time were measured before and after each training period. Significant, quantifiable c...

Learning, memory and a respiratory central pattern generator

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 1999

In an attempt to elucidate the causal mechanisms underlying learning and memory we have developed a model system, aerial respiration in the pond snail Lymnaea stagnalis. A three-neuron central pattern generator (CPG) whose sufficiency and necessity have been demonstrated mediates this behaviour. Aerial respiration, while an important homeostatic behaviour, is inhibited by the activation of the whole body withdrawal response that the animal uses to protect itself. We found that it was possible to operantly condition snails not to perform aerial respiration in a situation, a hypoxic environment, where aerial respiration should predominate. Operant conditioning was achieved by eliciting the pneumostome withdrawal response, part of the whole body withdrawal response, each time the animal attempted to open its pneumostome to breathe. Yoked control animals did not demonstrate an alteration in breathing behaviour. Subsequently we determined neural correlates of this associative behaviour and found that neuronal changes are distributed throughout the CPG. This preparation may afford us the opportunity to determine the casual neuronal changes that underlie learning and memory of associative conditioning.

Associative learning and memory inLymnaea stagnalis: how well do they remember?

The Journal of Experimental Biology, 2003

Molluscan model systems for the study of learning and memory This is not by any means an exhaustive review of invertebrate model systems that have been used to study the neuronal and molecular mechanisms of learning and memory; the interested reader is directed to two recent excellent reviews on this subject (Sahley and Crow, 1998; Chase, 2002). We have also restricted our discussion to gastropod molluscs, but this should in no way be taken to mean that the truly groundbreaking work on the mechanisms of learning and memory using 'worms' (e.g. Caenorhabditis elegans) or insects such as Drosophila is not worth mentioning or pursuing but rather that space limitations preclude their inclusion. For much the same reason, the fascinating studies using cephalopod molluscs (e.g. octopus), which exhibit very sophisticated learning and memory capabilities, will also not be reviewed here. Some of the first studies in the 'modern' search for the engram took the comparative physiological and psychological approach. For example, in the early 1900s, Piéron (1911), Dawson (1911) and Thompson (1917) used snails in attempts to discover how learning occurred. However, these studies were, by and large, forgotten, and it really was not until tests that were more natural and meaningful to the organisms were used that a full appreciation of the learning capabilities of gastropods became apparent. The 1960s saw a burst of activity that is still evident today to study how the nervous system is 'wired-up' to mediate specific behaviours and how changes in the behaviour brought about by training procedures are reflected or caused (the real goal) by changes in the activity of specific neurons. Thus, preparations such as Aplysia, Hermissenda, Pleurobranchaea and Tritonia gained popularity. Eric Kandel, with his share of the Nobel Prize for Medicine and Physiology in 2000, attained one of the pinnacles of science in part by using Aplysia. All the species mentioned above are marine creatures, and, with few exceptions (e.g. the land slug Limax and the land snail Helix), conventional wisdom from the 1970s through to the early 1990s was that the freshwater gastropods just did not have the 'right stuff' to be used in the quest for the Holy Grail. This review will focus on why that conventional wisdom was incorrect and why using Lymnaea might just be a very useful path to take to grasp the Grail in hand. Lymnaea as a model system for neurobiology Until the Dutch, under the inspired leadership of Professors Lever and Joose in The Department of Biology at Vrije Universeit in Amsterdam, adopted Lymnaea as their animal of choice for study in the early 1970s, Lymnaea was not often used in neurobiological research. The natural history of the 2097

Modulation of aerial respiratory behaviour in a pond snail

Respiratory Physiology & Neurobiology, 2006

Aerial respiratory in Lymnaea is driven by a three-neuron CPG whose sufficiency and necessity has been directly demonstrated. While this CPG is 'hard-wired' it displays a tremendous amount of plasticity. That is, it is possible by employing specific training procedures to alter how it functions in a specific hypoxic environment. Thus, it is possible to study directly the causal mechanisms of long-term memory formation, forgetting, and modulation of the memory at a single cell level. Thus, it is possible to use a relatively simple three-neuron CPG to study not only important questions concerning regulation of important homeostatic mechanisms but to also use it to study how learning and non-declarative memory are mediated at a cellular level.

Novel neural correlates of operant conditioning in normal and differentially reared Lymnaea

The Journal of experimental biology, 2009

The aerial respiratory behaviour of the mollusc Lymnaea stagnalis is an important homeostatic behaviour that can be operantly conditioned. The central pattern generator underlying this behaviour, as well as motorneurons innervating the respiratory orifice, the pneumostome, have been identified and their activity can be monitored in the semi-intact preparation using electrophysiological recordings. In this study, we used both intact animals and semi-intact preparations to identify novel changes in the respiratory central pattern generator following operant conditioning. In addition, we reared animals in the absence of this respiratory behaviour throughout development, to investigate whether previous experience and activity-dependent plasticity during development are essential to allow neural plasticity in the adult. We found that animals raised normally (allowed to perform aerial respiratory behaviour) exhibited the expected reduction in aerial respiratory behaviour following operant...

Associative Learning Acquisition and Retention Depends on Developmental Stage in Lymnaea stagnalis

Neurobiology of Learning and Memory, 2002

Associative learning dependent on visual and vestibular sensory neurons and the underlying cellular mechanisms have been well characterized in Hermissenda but not yet in Lymnaea. Three days of conditioning with paired presentations of a light flash (conditional stimulus: CS) and orbital rotation (unconditional stimulus: UCS) in intact Lymnaea stagnalis results in a whole-body withdrawal response (WBWR) to the CS. In the current study, we examined the optimal stimulus conditions for associative learning, including developmental stage, number of stimuli, interstimulus interval, and intertrial interval. Animals with a shell length longer than 18 mm (sexually mature) acquired and retained the associative memory, while younger ones having a shell length shorter than 15 mm acquired but did not retain the memory to the following day. For mature animals, 10 paired presentations of the CS and UCS presented every 2 min were sufficient for the induction of a WBWR to the CS. Furthermore, animals conditioned with the UCS presented simultaneously with the last 2 s of the CS also exhibited a significant WBWR in response to the CS. Blind animals did not acquire the associative memory, suggesting that ocular photoreceptors, and not dermal photoreceptors, detected the CS. These results show that maturity was key to retention of associative learning. ᭧ 2002 Elsevier Science (USA)