Final answer:
In an extracellular recording with LTP induction, there will be an increased EPSP due to a larger number of AMPA receptors inserted into the postsynaptic membrane, leading to higher postsynaptic neuron excitability.
Step-by-step explanation:
When Long-term Potentiation (LTP) is induced, an extracellular recording would typically show heightened synaptic efficacy. This means that when glutamate is released from the presynaptic neuron, the postsynaptic neuron will exhibit a larger excitatory postsynaptic potential (EPSP) due to an increased number of AMPA receptors that have been inserted into the postsynaptic membrane.
The strengthened synapse ensures that the postsynaptic neuron is more likely to fire in response to the presynaptic neurotransmitter release.
The increase in synaptic strength is a result of a calcium- and CaMKII-dependent cellular cascade, which not only results in the insertion of more AMPA receptors but also enhances the conduction through these receptors. Consequently, upon subsequent glutamate release, a greater depolarization of the postsynaptic membrane occurs, effectively making the synapse more responsive to neurotransmitter signals.