After a much-too-long break following its April Fools Day season premiere, Rick and Morty finally returned to Adult Swim with a Mad Max: Fury Road sendup that sees Morty and Summer trying to deal with the impending divorce of their parents.
This being Rick and Morty, of course, there's little time for an in-depth exploration of their feelings; Summer goes full-on nihilistic cannibal, while Morty finds solace in smashing post-apocalyptic humans to a bloody pulp in the Thunder and/or Blood Dome (save your arguments for the Semantics Dome, E.B. White).
Morty—he of puny arms and weak constitution—becomes a ruthless killing machine after Rick transplants the "muscle memory" of a fallen warrior into one of Morty's arms. The arm starts thinking for itself, killing all-comers with impunity. Like most Rick and Morty gags, it is futuristic, seemingly totally infeasible, and at least sort of based on real science.
Would transplanted muscles retain "memories" from their donors?
In the episode, poor Morty's new arm immediately goes rogue. He's unable to control it, and it starts killing everyone who approaches him. This is, of course, extremely outlandish.
It's worth mentioning that certain muscles do function independently of the brain, in some sense (the heart has a built-in pacemaker and beats on its own). And there have been studies showing that in certain species of nematodes (roundworms), locomotion is possible without nervous system input at all.
A 2011 paper in the Journal of Physiology cites a sequence in the movie Burn After Reading in which George Clooney thanks "muscle memory" for performing a series of complex tasks that result in him shooting a man who surprised him. "Normally, Coen Brothers movies are not a reliable source for information about neuroscience," the paper reads. "But in this case they touched upon an interesting controversy: Can muscles really drive behavior independent of the nervous system?" It then cites several nematode studies in which their bodies "generate spontaneous voltage spikes independent of the nervous system."
We aren't nematodes, of course. Perhaps a better, more potentially realistic analogue would be that bit in The Matrix where Neo "downloads" the ability to do kung fu.
This hypothetical was put another way by a Quora user a couple years ago: "When will we be able to transmit muscle memory and abilities to one another? For example, one could get the muscle memory of [soccer star Lionel] Messi's skillful play and either copy it onto another person or a robot powered by AI."
Some recent research into the nature of muscle memory and motor function in general gives us cause for optimism here.
A scientific review of studies on the subject published in the Journal of Experimental Biology last year confirmed that muscle memory is indeed a thing, but the review noted only that there is "a cellular memory in skeletal muscle in which hypertrophy is 'remembered' such that a fiber that has previously been large, but subsequently lost its mass, can regain mass faster than naive fibers."
This means, then, that a muscle that was once strong can become strong again relatively quickly. This research found that this type of muscle memory happens in the muscle cells themselves (specifically, the myonuclei), not in the brain or nervous system.
Arm and hand transplants are in their infancy. But it's not so crazy that the arm transplanted to Morty, which used to belong to a man who watched his entire village burn to the ground, would become stronger faster than the one Morty was born with. His main arm exercise seems to be furtively masturbating.
Of course, having a particularly strong muscle doesn't necessarily mean you'd be able to instantly perform highly specialized fighting skills. For that, we would need something like we see in The Matrix. In order to transfer skills, we'd need instant human-to-human (or machine-to-human or human-to-machine) memory transfer.
In a Live Science article about the plausibility of Matrix-like skill downloads, Brown University neuroscience professor Takeo Watanabe (then of Boston University) notes that "motor learning is similar to perceptual learning." For our purposes, this is a good thing, because there is currently much science dedicated to manipulating, recovering, implanting, transferring, and destroying memories. These experiments are largely taking place in rats, snails, and other animals that are much less complex than humans. But if memories used in motor skill acquisition are similar to other types of memories, it stands to reason that perhaps one day far in the future we could manipulate and transfer them to facilitate instant learning.
It's at least plausible that, one day, Rick's muscle memory invention might not be so crazy after all
There is also a considerable amount of research being done right now into "decoded neurofeedback," a type of neuroscience in which participants are taught skills at a faster-than-normal rate by activating specific parts of the brain. Watanabe speculates that if such a process could be sped up, perhaps we'd be able to see some Matrix-like skill acquisition.
Scientists are also learning more about a controversial field of study called "genetic memory," which some say can help explain "savants" who are capable of performing complex tasks at a high level with little to no instruction.
"Genetic memory, simply put, is complex abilities and actual sophisticated knowledge inherited along with other more typical and commonly accepted physical and behavioral characteristics," Darold Treffert, a psychiatrist who studies "savant syndrome," wrote in a 2015 Scientific American article.
History is filled with examples of people who have suffered head injuries, strokes, or comas and have suddenly been able to sculpt or play music at a high level. "The challenge is how to tap that dormant capacity non-intrusively and without a brain injury or similar incident," Treffert wrote.
New genetic modification techniques like CRISPR are not only working to modify the genomes of embryos, but also to change DNA in adults; if the key to "genetic memory" is unlocked, then, it's at least plausible that, one day, Rick's muscle memory invention might not be so crazy after all. Most things we do are likely a combination of nature and nurture, so we'll likely need a mix of all of this technology plus some training on Morty's part. And then there's the question of transplantation rejection—but that's an adventure for another day.
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