What is temporal and spatial summation in synaptic transmission?

Synaptic transmission, whether chemical or electrical, results in a change in membrane potential of the post-synaptic cell. If an excitatory synapse is activated, this results in a depolarization of the post-synaptic neuron. If the same synapse is activated again, before the membrane potential of the post-synaptic neuron has returned to the resting potential, the same synaptic transmission will produce an even greater depolarization. This effect is temporal summation (adding up the changes in membrane potential over time). The same post-synaptic neuron can receive inputs from multiple pre-synaptic neurons. The membrane potential of the post-synaptic neuron is a result of the combination of these interactions. For example, if two excitatory synapses are activated, the post-synaptic neuron membrane potential will be greatly depolarized. If one excitatory synapse and one inhibitory synapse is activated, the result will be no change in membrane potential, a slight depolarization or a slight hyperpolarization (depending on the relative strength of the synapses). This effect is special summation (adding up the changes in different parts of the neuron).