Thread by @garwboy

When does short-term memory become long-term? How 'recent' does a memory need to be to be classed as the former, not the latter?

From a week ago? A day? Hours?

Actually, *60 seconds*. Max. Anything you remember from more than a minute ago is a long term memory

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#BrainStuff

Short-term and long-term memory are actually very different things, in terms of how they work in the brain. It's like comparing printed books to blackboards, or some other analogy which doesn't make me sound like I'm from the 19th century

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The main difference between long-long term and short-term memory is that long-term memories have a physical presence in the brain. Short term... doesn't. Not strictly speaking. It's more patterns of neurological activity. While still complex, they're way more fleeting.

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As far as we know, your basic unit of memory, the 'engram', is made up of dedicated synapses, connections between neurons. New information enters our brain, our brain thinks "I'll keep hold of this", and does so by creating some new neurological connections to represent it.

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That's one of the main things our hippocampus does. It takes sensory/cognitive/emotional information in, and forges new neural connections to represent that particular combination of info. I.e., it forms new memories.

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Aside: because we're constantly experiencing stuff and converting it to memories, our hippocampus is a v active and demanding brain region. So, even a brief disruption in vital resources (e.g. oxygen) can cause havoc with memory. That's why strokes can be so disruptive.

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Back to the point; long-term memories are ones our brains have created new physical connections to support. It's taken the time to 'write them down', so new synapses (and collections thereof) are to memory like ink and paper are to printed stories; couldn't exist without them

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However, as with writing things down, forming new neural connections for memories takes *time*. Some estimates suggest it takes up to a minute for the brain to reliably knit together neurons and form an enduring memory.

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That's not compatible with the world around us though. It moves too fast, changes too quickly. If we had to wait a whole minute before we could represent something in our heads, we'd have died out long ago. Most predators are faster than that.

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So, we have SHORT-term memory. This is information that we can retain right away, because it seems to be represented by patterns of activity in the frontal lobes, where we do our thinking. Much faster, no need to forge whole new connections.

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HowEVer, using distinct patterns of activity between neurons is a rapid way to store information, but not a robust or enduring one. It's like writing a shopping list in the condensation on your bathroom mirror, while the shower's running. Quick? Yes. Enduring? No.

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I hesitate to use the analogy as so many neurobods don't like it, but I can't think of a better one

Short-term memory is like your computer's processor, long-term memory is like the hard drive. One is faster, and can manipulate info, while the other is sturdier and enduring

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If anything, your brain's short term memory is surprisingly limited, in terms of capacity. Latest data suggest we can hold four 'things' in it at any one time.

What counts as a 'thing' varies from situation to situation, because brains be braining.

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Ultimately, if there's something we actively *want* to remember, we work to keep it in our short term memory, long enough for our sturdy but cumbersome long term memory processes to store it via neural connections.

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Hence we recite names, addresses, phone numbers, email addresses etc. if we don't want to forget them. It's gives our deeper brain processes the time required to lock them in to long-term memory.

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This is tricky, though. Not only does short term memory have a very limited capacity, new stuff is always trying to barge its way into it, because we're awake and experiencing new things all the time. That's why we can forget very recent things if distracted/interrupted

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In many ways, trying to keep something important in your short term memory is like trying to write down a brilliant idea on a blackboard, but one that's placed right in front of the entrance to a very busy train station. It's possible, but it's not easy.

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So that's why short-term memories last for a minute, max. That's how long our brain can sustain them. After that, they're saved as long-term memories, or gone.

Ever wandered into a room and thought "Why the hell did I come in here?" Well, now you know why that happened

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I guess the label 'short term' is more broadly used for other things, like leases, loans, relationships etc. which are on a different scale of brevity, hence short-term memory is usually assumed to last waaaaaaay longer than is the neurological reality.

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Anyway, that was some #BrainStuff I always found interesting. It, and much more like it, can be found in my debut book, The Idiot Brain, which is still going strong.

amazon.co.uk/Idiot-Brain-Ne…

amazon.co.uk/Idiot-Brain-Ne…

Thanks for reading (tolerating) this far

/end