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Memory trace in feeding neural circuitry underlying conditioned taste aversion in Lymnaea
Etsuro Ito1, Emi Otsuka, Noriyuki Hama
1Laboratory of Functional Biology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Japan. eito@kph.bunri-u.ac.jp
Plos One
|August 18, 2012
Summary
Long-term memory in pond snails involves changes in neural circuits. Taste aversion training enhances neurotransmitter release from the N3t cell, specifically facilitating its inhibitory connection to the N1M cell in the feeding central pattern generator.
Area of Science:
- Neuroscience
- Animal Behavior
- Cellular Biology
Background:
- The pond snail Lymnaea stagnalis exhibits long-term memory, specifically conditioned taste aversion (CTA).
- Previous research indicated altered synaptic responses in the feeding central pattern generator (CPG) following CTA training, involving the cerebral giant cell (CGC) and neuron 1 medial (N1M) cell.
Purpose of the Study:
- To investigate the specific synaptic changes underlying long-term memory in Lymnaea stagnalis CTA.
- To elucidate the role of the neuron 3 tonic (N3t) cell in the neural circuit mediating CTA memory.
Main Methods:
- Electrophysiological recordings were used to monitor synaptic inputs in isolated snail brains.
- Monitored monosynaptic excitatory postsynaptic potentials (EPSPs) in B1 and B3 motor neurons, representing inputs from the CGC to the N3t cell and from the N3t cell to the N1M cell, respectively.
Main Results:
- While synaptic inputs from the CGC to the N3t cell (monitored via B1 neurons) showed no change after CTA training.
- Spontaneous monosynaptic EPSPs from the N3t cell to the B3 motor neurons were significantly enlarged following CTA training.
Conclusions:
- CTA training specifically facilitates the monosynaptic inputs from the N3t cell to downstream neurons, including the N1M cell.
- This facilitation is attributed to increased neurotransmitter release from the N3t cell, representing a memory trace for CTA.
- The N3t cell's inhibitory action on the N1M cell is strengthened in response to conditioned stimuli, contributing to CTA memory in Lymnaea.
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