- Long-term potentiation (LTP) is a fundamental process in synaptic plasticity and is widely considered a key cellular mechanism underlying learning and memory.
- LTP occurs primarily at the postsynaptic sites of excitatory synapses.

- The correct answer is Dendritic spines.
- These small, membranous protrusions on the dendrites provide the structural basis for synaptic connections where neurotransmitters bind and initiate intracellular signaling cascades that strengthen synaptic transmission.
- The increase in synaptic strength during LTP is largely due to the insertion and phosphorylation of AMPA receptors at these dendritic spines, enhancing their responsiveness to glutamate.

Other options such as the axon hillock and cell body are important for action potential initiation and integration, but they are not the primary sites where synaptic strengthening through LTP takes place. The presynaptic terminal is involved in neurotransmitter release, but LTP mainly involves postsynaptic modifications.

In summary:
- LTP predominantly occurs at dendritic spines, the site of excitatory synaptic input.
- It involves postsynaptic changes such as increased AMPA receptor density.
- This synaptic enhancement underlies learning and memory processes.

Reference: Kandel E.R., Schwartz J.H., Jessell T.M. Principles of Neural Science, 5th Edition, Chapter 51, Page 1224