Complex sentence: The theory is often summarized as "cells that fire together, wire together", a simplified and figurative way of putting the theory of "associative learning" in which simultaneous activation of cells leads to pronounced increases in synaptic strength between those cells.
Split into simpler sentences: The theory is often summarized as "cells that fire together, wire together", a simplified and figurative way of putting the theory. It purports to explain "associative learning", in which simultaneous activation of cells leads to pronounced increases in synaptic strength between those cells.