Associative Learning-Induced Synaptic Potentiation at the Two Major Hippocampal CA1 Inputs for Cued Memory...

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Learning and Memory

Background:

• Functional plasticity at hippocampal synapses is critical for learning and memory.
• The specific mechanisms of learning-associated synaptic plasticity in the dorsal CA1 hippocampus (dCA1) are not well understood.

Purpose of the Study:

• To investigate learning-induced synaptic plasticity in the dCA1 following a single session of reward-based trace conditioning.
• To identify the specific hippocampal pathways involved in this plasticity.

Main Methods:

• Local field-potential recording and optogenetic inhibition in the dCA1.
• NMDA receptor blockade during conditioning.
• Whole-cell recording of sensory-evoked synaptic responses in dCA1 neurons.
• Multiple-site recording to track plasticity time course.

Main Results:

• Conditioning increased dCA1 synaptic responses to the conditioned stimulus (CS) at both Schaffer collaterals (Rad) and temporoammonic (LMol) inputs.
• Synaptic potentiation of CS-responding excitatory synapses was confirmed at both pathways.
• The time course of synaptic potentiation in Rad and LMol emerged later and saturated earlier than behavioral responses.

Conclusions:

• Reward-based trace conditioning induces functional synaptic plasticity in the dCA1.
• This plasticity occurs at both Schaffer collateral and temporoammonic pathways.
• The findings demonstrate a cued memory-associated synaptic plasticity in the hippocampus.