. . . that there are three main stages in the formation and retrieval of memory?
Encoding or registration
(processing and combining of received information)
(creation of a permanent record of the encoded information)
Retrieval or recall
(calling back the stored information in response to some cue for use in a process or activity)
See this excellent and thorough article from Wikpedia.
"In recent decades, [memory] has become one of the principal pillars of a new branch of science called cognitive neuroscience, a marriage between cognitive psychology and neuroscience."