A new paper, however, says different. Philadelphia's Joshua Jacobs et al report that they found a spot in the left temporal lobe of a male patient, stimulation of which evoked memories of the man's time at high school. The guy was in his 30s at the time, so these are quite distant memories.
When it first happened, he is reported to have said:
Iʼm, like, remembering stuff from, like, high school…. Why is this suddenly popping in my head?Repeated stimulation of the same electrode - but not nearby electrodes - caused other high school memories to emerge.
Even more interestingly, when the same stimulating electrode was used to record activity during memory retrieval, the "high school spot" was found to be significantly less active when high school was being remembered, compared to when various other kinds of memories were being accessed.
This graph shows that all kinds of memories evoked high-frequency activity in the high-school zone, but high-school memories did so less:
No other electrode location caused the same effects (or indeed, any detectable memory effects), although as you can see on the image at the top, the electrode coverage was not huge.
A little background: the guy had these electrodes in place because he suffered from epilepsy, resistant to medication, which was believed to originate in the temporal lobe. Temporal lobe epilepsy can cause memory phenomena rather like this, but this patient had never experienced that, and the electrically-evoked memories were experienced as entirely novel.
It's a nice case report and it raises many questions. Why is the high-school spot less active during memory retrieval? That seems the wrong way around (I did a double-take to make sure I was reading it properly).
And what would happen if you somehow disabled (or overactivated) this area, and asked him to remember a particular school memory? Would he draw a blank, or would he remember it but without the "high-school-ness"? What would that feel like?
Either way, this case suggests that memories are stored in the brain "by topic", in the sense that "similar" memories are associated with nearby areas of the brain. At least sometimes. But then, why didn't nearby electrodes evoke other memories? If there's a high-school spot, why not a kindergarten spot, a my-first-job spot?
Maybe those spots lay in areas with no electrode coverage... but the fact that many temporal electrodes didn't bring back any memories suggests that there's lots of cortex which isn't part of a "spot". Perhaps those areas are "spare", waiting to be used up? Clearly, he wasn't born with a high school spot. It must have emerged during high school. But in that case there had to be a "blank" area first.
Jacobs J, Lega B, and Anderson C (2011). Explaining How Brain Stimulation Can Evoke Memories. Journal of cognitive neuroscience PMID: 22098266
8 comments:
I enjoyed this material. Thanks. ... Unfortunately, your list of maybes must allow for a LOT of unknown variables and a much larger pool of subjects. It is entirely unknown what this man's emotional/logical/experiential links between high school and elementary school are, for example, although we might assume they would be associated by topic. Or such memories could be suffused in a larger matrix of "school" cell connections that are simply too specific for this early probing to detect. ... It will be interesting to see what avenues of research arise from this.
I can not access articles on the MIT Press. Did they do a control?
Maybe what is being stimulated are functional areas of the brain that are more dominant at certain stages of development. Maybe Piaget's cognitive stages have a ever-present representation in the brain and stimulation of those regions causes these effects - ie it's not about memories but about stage.
Maybe maybe. Makes a good story doesn't it? Beware!
"(...)the "high school spot" was found to be significantly less active when high school was being remembered,(...)Why is the high-school spot less active during memory retrieval? That seems the wrong way around (...)"
I agree with you: this is interesting.
Could it be that a normal human brain is inhibiting emotional memories to "surface" unless a sensation or a will to remember something activate neurons in order to inhibit the inhibition?
Also ECT -a useful treatment for some cases- causes firing of many neurons and gives memory troubles as a side effect. And so does valium and alcohol acute intoxication.
DS: They had two kinds of controls - the other electrodes, none of which produced the same effects.
And they used other "non high school" memories. High school memories caused less activation compared to those control memories at the electrode in question, but no others.
However the control memories were not ideal because they were either general knowledge, or more recent memories e.g. "Who interviewed you for your current job".
So it might be that that electode is not for high school so much as the time of high school. Would be interesting to ask him about something else that happened during high school; but then, when you're at school, most of your memories are school related. Even say 9/11, I bet most school kids heard about it "at school" and that's what they'll remember.
So it's hard to distinguish.
I'm the author of the paper and was excited to come across this post. Thanks for everyone's interest.
A PDF copy of the manuscript is available on my website http://jacobs.biomed.drexel.edu/.
In response to some of the comments, I entirely agree that it would have been great to do more control studies on this patient. Unfortunately we only had a few hours to test this patient before his electrodes were explanted, so more controls were not possible.
Hi Josh, thanks for the comment and congrats on a great paper. Yes, it's easy enough for us to ask for more control experiments but that doesn't always mean it's possible...:)
Hy. I just stopped to thank you for your posts as they proved to be really useful as research material.
I write for a legal blog and this month I had to deal with a lot of articles about medical lawsuits and malpraxis , as well as lawsuits resulting from improper use of pharmaceutical products and negative side-effects of drugs.
Post a Comment