Why do my hands remember things that my brain doesn't?
July 30, 2005 7:31 AM   Subscribe

memory-filter: Why or how does the body seem to remember learned physical action sequences before you can mentally recall what they are?

I wonder about this almost every week because I open up a money safe with a combination lock at my job on saturdays. I usually have a hard time trying to recall what the safe combination is, but if I just start turning the dial, then I remember the numbers as I turn. If I try to recall the numbers without physically unlocking it, I can still usually do it, but it takes much longer to remember.

There's probably some technical explanation for this among neuroscientists, but bonus points for explaining in simple enough terms that I don't completely lose interest.
posted by p3t3 to Science & Nature (16 answers total)
I think it's muscle memory or proprioception - it's the same concept behind martial arts katas and military training like fire and movement - the idea is that you continually perform the same action until the body "learns" the required action and can perform it without you having to concentrate on the task.

It's useful in the above circumstances as it does not rely on you thinking about your actions which can be spectacularly fatal or dangerous if you pause to think.

I have the same thing with all the telephone numbers I need to recall as part of my job which is dead handy sometimes...
posted by longbaugh at 7:56 AM on July 30, 2005

"I usually have a hard time trying to recall what the safe combination is, but if I just start turning the dial, then I remember the numbers as I turn."

This seems more like a memory that is linked to motor performance, rather than proprioception. It's like when you associate two things together, and remembering one thing automatically evokes the other.
posted by Gyan at 8:14 AM on July 30, 2005

This topic was touched on yesterday on Science Friday.

I experience this when trying to recall songs on guitar that I haven't played in a while. It's as if each hand position is stored relative to the one before it. If I can remember a bar or two, I can unlock the entire song.
posted by crumbly at 8:24 AM on July 30, 2005

@ Gyan- Sort of like how smells trigger memories then?

Thanks as well for the NPR and Wikipedia links. I've read some Oliver Sacks type neuropsych books in the past, and reading up on some of this info is retriggering my interest in these types of things.

Maybe I'll look for another good book on the subject for my leisure reading.
posted by p3t3 at 8:32 AM on July 30, 2005

It's cerebellar. Proprioception is the ability to tell where your joints are in space. Very different.

The cerebellum is the primary area responsible for "muscle memory." The cerebellum remembers series of motions--like tying a tie, or opening a bank vault--through error-checking neural circuits.

When you're a kid, for example, and you reach out to pick up a cup full of water and accidentally knock it over, your eyes register that your muscles didn't successfully complete the action you wanted them to. This sends a strong signal to the cerebellum that "oops, the muscle pattern was off a bit--too fast, too slow, too strong, too much to the right, etc." And so next time, your muscles will correct for that when you reach for something again.

That's why practice makes perfect, and you get better at things after repetition. Your cerebellum gets used to the series of muscle movements, and has a huge number of times to correct any errors made during the sequence, so that you can do the action faster or more error-proof.
posted by gramcracker at 8:38 AM on July 30, 2005

Apologies for referring to it as proprioception - I have always called it muscle memory and that is simply where the wiki took me when I looked it up. You might also search under the terms "kinesthetic memory", "neuro-muscular facilitation" or "sensory-motor learning".
posted by longbaugh at 8:50 AM on July 30, 2005

Ah, so that's why I don't have to remember people's phone numbers. I just pick up the phone and think "call mom" and it happens.
posted by oaf at 9:52 AM on July 30, 2005

Well, there's that and the fact that she's had the same phone number since before I was born. So I guess I really mean commonly-used phone numbers, not just any phone numbers.
posted by oaf at 9:55 AM on July 30, 2005

The inferior olivary nucleus is probably more important than the cerebellum for what we neurologists call "motor learning," although those structures are adjacent and intimately connected. The cerebellum's effects we tend to think of as modulatory (as in gramcracker's excellent description), rather than as a generator of movement. But the storage seems to happen in or owing to the neuronal activity in the inferior olive. ("Muscle memory" is a term I've heard, but muscles don't really remember anything.)

Proprioception refers to the sensory ability to detect what angle your joints are at; and particularly the ability to detect movement around a joint. It's extremely highly developed. I test it by having a patient close their eyes, grasping their index finger past the first knuckle (on the sides, so pressure cues do not give me away), and flexing the joint minutely up or down. Normal people can easily detect the direction of deflections that move the fingertip less than a millimeter. Unsurprisingly, if proprioception is broken for whatever reason, motor learning becomes impaired.

"Conscious" recall is a language function and lives in the left parietal and temporal areas, especially the hippocampus.
posted by ikkyu2 at 12:04 PM on July 30, 2005

"Conscious" recall is a language function and lives in the left parietal and temporal areas, especially the hippocampus.

I guess we (or at least I) generally tend to think of the brain as one big machine, when it's acutally lots of smaller ones that don't always have perfect cross-referencing abilities. It seems like the "conscious" memory should have access to all the other memory functions, but the brain doesn't necessarily work that way. Interesting stuff. Thanks again to everyone.
posted by p3t3 at 1:07 PM on July 30, 2005

A lot of the learning is in your spinal cord, not your brain. Your spinal cord has "grey matter" in it, or to put it another way, the learning material of your brain extends all the way down your spine.

A reason for this is nerve signal speed. Nerve signals are slow. If the neural processing happens closer to the muscles, reflexes are faster. Nerve signal speed can be massivly sped up via mylination, but a mylinated nerve is much MUCH fatter, so you can't clump many of them, and there are other drawbacks.

The speed difference due to mylination and difference in distance between hand to spine and hand to brain is also why if you touch a dangeriously hot (or cold) surface, your hand will jump back from it immediately, even though you won't be able to immediately feel whether it was hot or cold.

So one reason you can't consciously access muscle memory is that it's purpose is to be physically closer to the muscles, which in turn makes it farther from the bulk of the brain, and thus more independant from it.
posted by -harlequin- at 7:25 PM on July 30, 2005

I'm like this with passwords. Sometimes I have to actually *type* a password at work before I can tell a coworker what it is. My fingers remember it, but my mind doesn't.
posted by mrbill at 12:20 AM on July 31, 2005

A lot of the learning is in your spinal cord, not your brain. Your spinal cord has "grey matter" in it, or to put it another way, the learning material of your brain extends all the way down your spine.

Grey matter is processing material (connected by 'white' matter). But not all grey matter can learn, diffrent parts of the brain can do diffrent things.
posted by delmoi at 2:51 PM on July 31, 2005

Actualy human motion involves two parts of the brain The first part (The cerebellum, IIRC) creates a "plan" which gets sent to another part (the motor cortex?) which is aranged as a big grid. Each single action is then sent out at the right moment. by that part of the brain.

I would guess that cerebellum stores these plans in short term memory, and if they're used over and over again get stored in long term memory. The numbers of the combination/phone number 'emerge' from that stored plan, without you actualy needing to remember those bits of information.
posted by delmoi at 2:58 PM on July 31, 2005

Others have answered this far more effectively than I can, but I can tell you two personal experiences with muscle memory — even though I no longer have any idea whatsoever how to play piano, my fingers can still do a good chunk of "Star Wars" on their own.

And given the fact that I can type while half-awake or even partly unconscious (neither of which are the case at the moment), I have a feeling some of my typing ability is in my muscle memory now, too. :)
posted by WCityMike at 3:54 PM on July 31, 2005

Great question!

I've noticed this with certain PS2 games that I've played to death (eg. SSX). If someone grabs the control and asks me how to play I simply cannot answer. I need to hold the controller and pretend I'm actually playing before I can articulate how the buttons work.

It feels stupid for a game I know so well... but now I'm glad this knowledge isn't wasting space in my valuable hippocampus.
posted by bruceyeah at 7:56 PM on August 1, 2005

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