Complex sentence: In neuroscience, an excitatory postsynaptic potential (EPSP) is a temporary increase in postsynaptic membrane potential caused by the flow of positively-charged ions into the postsynaptic cell.
Split into simpler sentences: In neuroscience, an excitatory postsynaptic potential (EPSP) is a temporary increase in postsynaptic membrane potential. EPSPs are caused by the flow of positively-charged ions into the postsynaptic cell.