Final answer:
Long-term potentiation (LTP) is a sustained increase in synaptic strength, while long-term depression (LTD) is a decrease, both critical for synaptic plasticity, transmission of neural impulses, and the biological foundations of learning and memory.
Step-by-step explanation:
Long-term potentiation (LTP) and long-term depression (LTD) are important mechanisms that underlie synaptic plasticity, crucial for learning, memory and changes in neural connectivity. LTP is characterized by a prolonged increase in synaptic strength while LTD involves a decrease. During LTP, repeated stimulation of a synapse leads to calcium and CaMKII-dependent mechanisms that insert additional AMPA receptors into the postsynaptic membrane, enhancing the cell's responsiveness to glutamate. On the other hand, LTD involves a reduction of AMPA receptors from the postsynaptic membrane due to a lower presynaptic firing rate, which triggers cascades involving calcineurin and protein phosphatase 1.
These processes are critical for modifying synaptic connectivity to facilitate learning and memory and are often studied in the context of the hippocampus, a brain region intimately involved in these cognitive functions. Therefore, LTP has been proposed as the mechanism for learning and memory, crucial for the transmission of impulses across synapses and overall neural adaptation.