Long-term potentiation (LTP) at hippocampal synapses requires NMDA receptor activation. The 'Hebbian' property of NMDA receptors that makes them ideal for coincidence detection is:

• A Activation requires only presynaptic glutamate release with high affinity binding
• B Both glutamate (presynaptic) AND postsynaptic depolarisation (removing Mg2+ block) are required simultaneously ✓
• C NMDA receptors are purely postsynaptic ligand-gated channels without voltage dependence
• D Repeated activation desensitises NMDA receptors, strengthening non-NMDA pathways

Explanation

NMDA receptors are unique 'coincidence detectors' because they require two simultaneous conditions to open: (1) binding of glutamate and glycine (co-agonists) from the presynaptic neuron, AND (2) postsynaptic depolarisation to relieve the Mg2+ block that occludes the channel at resting potential. This dual requirement means NMDA receptors only conduct when pre- and postsynaptic activity coincide — the cellular basis of Hebbian plasticity ('neurons that fire together, wire together'). Ca2+ entry through activated NMDA receptors triggers AMPA receptor insertion and LTP.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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