A new study, conducted at the University of Pennsylvania, by Sean Polyn, PhD, and reported today in the journal Science, demonstrates that memory is the brain's effort to return to a past state. It is not simply a recalling of fact or envisioning of the past, but rather a mechanism by which the brain recreates the chemical and neurological state of its organization at a past time.

Daniel DeNoon, writing for WebMD, calls it "mental time travel". The discovery that the physiological activity of the brain could be traced directly to what kind of information is being taken in or remembered, leads researchers to believe that the brain remembers by returning itself to a physiological framework as close as possible to that it knew in the moment to be remembered.

The study presented subjects with images of faces, places and common objects. Using functional magnetic resonance imaging (fMRI), researchers were able to detect and record which parts of the subjects' brains were active in perceiving each of the stimuli.

When subjects were later asked to recall the images they had seen, in any order at their whim, while the fMRI again scanned for brain activity, Dr. Polyn's team found that just before the volunteers named the stimulus they were recalling, the fMRI showed their brain state to be indicative of encountering a certain class of image —face, place or object— matching the state recorded in the initial perception.

The brain scans were, as such, able to tell the researchers as long as 5 seconds before the subjects did, what class of object they were remembering. In essence, the "constellation" of neurological properties is not "viewed" anew by the brain, but experienced as it was in the initial encounter.

At the level of everyday experience, it helps to explain why remembering where we were, or whom we were speaking with, just before misplacing something like keys or a wallet can help bring us to a recognition of where the object is. We retrace our steps by situating our mind to experience the relevant environment again, ideally leading us to the needed hints of memory.

It may also help to explain the neurochemical bases for "muscle memory", which musicians and athletes rely upon to function at high levels and which some believe drives cardiovascular function, tactile sensation and metabolism to "participate" in our memories of powerful or traumatic events. [s]