Final answer:
When the presynaptic neuron fires just before the postsynaptic neuron, it may lead to strengthening of the synapse through Long-Term Potentiation (LTP), influenced by the timing of action potentials. This is part of the synaptic summation process which includes both spatial and temporal summation of excitatory and inhibitory postsynaptic potentials to reach the threshold for an action potential.
Step-by-step explanation:
When a presynaptic neuron fires 10ms before the postsynaptic neuron consistently, we typically observe an effect related to Spike-Timing-Dependent Plasticity (STDP). STDP is a biological process that adjusts the strength of the connection, or synapse, between neurons based on the timing of their activity. Specifically, if a presynaptic neuron fires shortly before a postsynaptic neuron and this pattern is repeated, the synaptic strength is usually increased, which is known as Long-Term Potentiation (LTP). This effect is a part of the synaptic summation process where excitatory postsynaptic potentials (EPSPs) combine to sufficiently depolarize the postsynaptic neuron, possibly triggering an action potential if the cumulative depolarization exceeds the threshold.
The summation process can involve spatial summation, where multiple presynaptic inputs located at different sites on the neuron contribute to the overall depolarization. However, a single EPSP may not always be enough to induce an action potential; thus, the temporal summation of multiple EPSPs can be critical. Moreover, the presence of inhibitory postsynaptic potentials (IPSPs) can counteract the effect of EPSPs, influencing whether the neuron reaches the threshold to fire an action potential. The integration of both EPSPs and IPSPs at the axon hillock determines the net change in membrane potential and whether it will cross the threshold for an action potential.