Final answer:
Summation is the process by which multiple EPSPs can combine to trigger an action potential in a neuron, while spatial summation refers to simultaneous stimulation at different synapses. Long-term potentiation enhances synaptic connections through increased AMPA receptor insertion, crucial for learning and memory.
Step-by-step explanation:
Summation occurs when new EPSPs develop before previous ones have decayed, leading to a stronger collective depolarization that can trigger an action potential. This process is key in determining whether a neuron will fire based on the net change in voltage. Conversely, spatial summation occurs when a neuron is stimulated at several different locations by various presynaptic neurons potentially creating EPSPs and IPSPs. The integration of these various excitatory and inhibitory inputs occurs at the axon hillock and determines if the threshold for action potential is reached.
Long-term potentiation (LTP) and long-term depression (LTD) are processes related to the strengthening and weakening, respectively, of synaptic connections. LTP reinforces the association between neurons that frequently activate together, making future responses to a given stimulus stronger. This mechanical change involves inserting more AMPA receptors into the postsynaptic membrane, increasing its sensitivity to neurotransmitters. Meanwhile, LTD represents the opposite end, where less-used connections become weaker, demonstrating synaptic plasticity's dynamic nature and its critical role in learning and memory.