A little thread on #neuroscience #history. I was sorting my PDF collection and came across an old review paper from Perrot & Penfield summarizing an amazing number of cases (1132!) where #brain stimulation was used in presurgical mapping

https://academic.oup.com/brain/article-abstract/86/4/595/321416?redirectedFrom=fulltext

I downloaded the paper a long time ago after a conversation with Endel #Tulving about #EpisodicMemory and the brain. Penfield's work was often (loosely) considered as evidence that the #brain recorded experience that could be played back.

Once I got the paper, one thing of note is that the occurrence of anything resembling memory recall from stimulation was in a small number of patients - about 8% and only when the #TemporalLobe was stimulated. Interestingly, 10% showed what was classed as hallucinations.

This does have some implications for popular notions of how memory works, but even then, Penfield acknowledged that memory was not a localized phenomena, but rather distributed. The stimulation results activated circuits of "functionally connected" neurons.

NB: this is one of the first uses of the word "functional connectivity" in #neuroscience. Penfield uses it in his 1958 paper as well. It's not used the same way nowadays but has similar connotations that neurons can be linked in circuits that underlie a particular function.

Sidebar: the origin of "functional connectivity" that we use in #Network #Neuroscience these days comes from multi-cell recording work of Gerstein & Perkel.

https://www.cell.com/biophysj/pdf/S0006-3495(72)86097-1.pdf

Anyway, Penfield did acknowledge a potentially central role for hippocampus in memory as being a neural record of experience. Remember this is the late 1950's and early '60s when the temporal lobectomy work from Scoville & Milner was relatively new!

There definitely has been a ton of work since then that refines these observations, but I am still struck that the incidence of elaborate experience evocation from focal stimulation is still small - only 4% in the work cited below with rhinal cortex stimulation.

One can debate the implications for our concepts of #memory and #brain (e.g., local vs. distributed; veridical record vs. informed reconstruction). But today I'd rather say that it's worth reading this old literature to see how brain theories have evolved. /fin