Brains more complicated than previously thought

Neu­rons aren’t sim­ple lit­tle ma­chines, ax­ons talk to each other.

He and his col­leagues first dis­cov­ered in­di­vi­d­ual nerve cells can fire off sig­nals even in the ab­sence of elec­tri­cal stim­u­la­tions in the cell body or den­drites. It’s not always stim­u­lus in, im­me­di­ate ac­tion po­ten­tial out. (Ac­tion po­ten­tials are the fun­da­men­tal elec­tri­cal sig­nal­ing el­e­ments used by neu­rons; they are very brief changes in the mem­brane voltage of the neu­ron.)
“This cel­lu­lar mem­ory is a nov­elty,” Sprus­ton said. “The neu­ron is re­spond­ing to the his­tory of what hap­pened to it in the minute or so be­fore.” Sprus­ton and Sheffield found that the cel­lu­lar mem­ory is stored in the axon and the ac­tion po­ten­tial is gen­er­ated farther down the axon than they would have ex­pected. In­stead of be­ing near the cell body it oc­curs to­ward the end of the axon.
Their stud­ies of in­di­vi­d­ual neu­rons (from the hip­pocam­pus and neo­cor­tex of mice) led to ex­per­i­ments with mul­ti­ple neu­rons, which re­sulted in per­haps the biggest sur­prise of all. The re­searchers found that one axon can talk to an­other. They stim­u­lated one neu­ron, and de­tected the per­sis­tent firing in the other un­stim­u­lated neu­ron.
No den­drites or cell bod­ies were in­volved in this com­mu­ni­ca­tion. “The ax­ons are talk­ing to each other, but it’s a com­plete mys­tery as to how it works,” Sprus­ton said. “The next big ques­tion is: how wide­spread is this be­hav­ior? Is this an odd­ity or does in hap­pen in lots of neu­rons? We don’t think it’s rare, so it’s im­por­tant for us to un­der­stand un­der what con­di­tions it oc­curs and how this hap­pens.”

The origi­nal ar­ti­cle (pay­wall).

As­sum­ing this is all true, how does it af­fect the fea­si­bil­ity of up­load­ing? Any­one want to bet on whether things are even more com­pli­cated than the cur­rent dis­cov­er­ies?

ETA: It seems un­likely to me that you have to simu­late ev­ery atom to up­load a per­son, and more un­likely that it’s enough to view neu­rons as bi­nary switches. Is there any good way to think about how much ab­strac­tion you can get away with in up­load­ing?

Yes, I know it’s a vague stan­dard. I’m not sure how good an up­load needs to be. How good would be good enough for you?