I recall listening to a Radiolab (Radiolab: Podcasts | WNYC Studios | Podcasts) episode where Robert Krulwich made an analogy about the sequence of events that takes place when we do any action. I think he talked about “wagging your tongue”. First, the brain decides it wants to wag the tongue. “Mission control, we need to wag the tongue”. Then, the brain sends signals to the tongue which makes it wag. Then, there is some feedback to the brain indicating the the tongue did, indeed, wag. “Mission control, we have tongue wag confirmation. The tongue is wagging.”
I can’t seem to find the episode and/or clip despite hours of searching.
Part of the trouble with my search was that the topic had nothing to do with “tongues”. Instead, Robert simply used “tongue wagging” as an analogy for some other topic.
In fact, I’d run across the Radiolab episode you mentioned during my search. I listened to it (and its part 2) again, to be sure I hadn’t missed something. Unfortunately, neither was the episode I was seeking.
However, your post did make me rethink how I was thinking. I was searching with terms like “tongue” and “brain”. Instead, I thought, “What might a conversation between the brain and an extremity be an analogy for?” and that reminded me of the phenomenon of “phantom limbs”. I imagined that Robert was using the “tongue wagging” analogy to describe the way the brain communicates with an extremity…even one that isn’t there.
One search and listen later, and I’d found my episode: The Butcher's Assistant (starting at 1:10).