It is true that the article you posted later in response to my queries does indeed contain references to the term "SPW". Thank you for providing that clarifying link.
Unfortunately the terminology and origin of the term "SPW" (or "SPW-R")remains unknown to me, despite the second article using it freely. The article says, for example:
"... John O'Keefe investigated SPW-Rs in more detail in 1978 while studying the spatial memory of rat..."
Queries on Google seem to indicate that the term "SPW-R" refers to the same concept as the acronym "SWR" (a true acronym), but I'll never know, being too impatient to consider the matter further.