The Hebb Synapse Before Hebb: Theories of Synaptic Function in Learning and Memory Before , With a Discussion of the Long-Lost Synaptic Theory of William McDougall.

Since the work of Semon was rediscovered by Schacter in 1978, there has been a renewed interest is searching for the "engram" as the locus of memory in the brain and Hebb's cell assembly has been equated with Semon's engram. There have been many theories of memory involving some concept of synaptic change, culminating in the "Hebb Synapse" theory in 1949. However, Hebb said that the idea that any two cells or systems of cells that are repeatedly active at the same time will tend to become "associated," was not his idea, but an old one.