Film still from "The Brain That Wouldn't Die", Sterling Productions
The flatworm can regenerate its entire brain in only a few days, and so scientists decapitate them, but the worms retain memory of a previous experiment, despite having lost their head, and how this works is unexplained, although it implies that information is stored somewhere else besides the head.
Smells are encoded into memory via the limbic system, and this means recording body-states along with the smells. Our body remembers the way it felt the last time that smell was received. We know that a phantom limb remains in the brain, despite its having been amputated, but does a memory remain in the body despite having lost its head? It should be interesting to note here that odor receptors are all over the body, in organs and even in muscle tissue.
phys.org, August 2013
"An automated training paradigm reveals long-term memory in planaria and its persistence through head regeneration" Journal of Experimental Biology jeb.087809 First posted online July 2, 2013, DOI: 10.1242/jeb.087809