Don Hebb

This all comes from Don Hebb's paper from 1949.
CAs are the basis of psychological concepts.
The CA is activated by (among other things) the presentation of an instance of the concept.
A dog is presented and your dog CA may start to reverberate.
As long as its reverberating, the concept is in short term memory.
The concept is formed by synaptic weight modification (and more) driven by presentation from the environment.
It uses the Hebbian learning rule for which Hebb is more famous.
We've got a CA review paper with the editor of Biological Cybernetics.
There's scads of evidence in a range of animals.
It's best from single unit recording, but there's also evidence from fMRI, MEG, transcranial magnetic stimulus, and others.
It looks like they're all over the cortex except maybe V1, and in some sub-cortical areas.
CAs often cross brain areas.