Not actually “mental time travel” at all, is it?

Paul Raven @ 19-07-2011

But it makes for an attention-grabbing skiffy-tastic headline, AMIRITEZ? The actual story here is rather less OMFG: University of Pennsylvania have obtained the first neurobiological evidence in support of the theory of episodic memory.

“Theories of episodic memory suggest that when I remember an event, I retrieve its earlier context and make it part of my present context,” Kahana said.  “When I remember my grandmother, for example, I pull back all sorts of associations of a different time and place in my life; I’m also remembering living in Detroit and her Hungarian cooking. It’s like mental time travel. I jump back in time to the past, but I’m still grounded in the present.”

Jumping back in time to perceptions of the past while still grounded in the present? Strikes me that rewatching old home movies is at least as good a metaphor as time travel, but I’ll grant you that a lot less people would have reported it if it were pitched that way.

Neuroscience is still a fairly new scientific frontier, and while the last decade has seen the arrival of amazing new tools (and enhancements of existing ones), I believe it’s fair to say that these methods are still pretty crude, and the interpretations of results somewhat speculative. But even so, it’s interesting to see these early phases of our attempts to measure something as inherently intangible as the mind:

The memory experiment consisted of patients memorizing lists of 15 unrelated words. After seeing a list of the words in sequence, the subjects were distracted by doing simple arithmetic problems. They were then asked to recall as many words as they could in any order. Their implanted electrodes measured their brain activity at each step, and each subject read and recalled dozens of lists to ensure reliable data.

“By examining the patterns of brain activity recorded from the implanted electrodes,” Manning said, “we can measure when the brain’s activity is similar to a previously recorded pattern. When a patient recalls a word, their brain activity is similar to when they studied the same word.   In addition, the patterns at recall contained traces of other words that were studied prior to the recalled word.”

“What seems to be happening is that when patients recall a word, they bring back not only the thoughts associated with the word itself but also remnants of thoughts associated with other words they studied nearby in time,” he said.

The findings provide a brain-based explanation of a memory phenomenon that people experience every day.

“This is why two friends you met at different points in your life can become linked in your memory,” Kahana said. “Along your autobiographical timeline, contextual associations will exist at every time scale, from experiences that take place over the course of years to experiences that take place over the course of minutes, like studying words on a list.”