Final answer:
The enhancement of the postsynaptic cell's response to repeated stimuli is known as facilitation, which plays a key role in long-term potentiation (LTP), a process critically involved in learning and memory.
Step-by-step explanation:
The enhancement of the postsynaptic cell's response to a repeated stimulus is known as D. facilitation. This process is a fundamental component of long-term potentiation (LTP). LTP is a durable increase in signal transmission between two neurons that results from their synchronous stimulation and is essential in learning and memory formation. The principle behind LTP is 'cells that fire together wire together.' When NMDA receptors on the postsynaptic cell become unblocked due to repeated depolarization, a cascade of events is triggered, leading to the insertion of AMPA receptors into the postsynaptic membrane, which in turn increases the probability of postsynaptic neuron firing upon subsequent stimulation.