This is a part of the Hot Topic podcast series from the Model Systems Knowledge Translation Center on Changes in Memory After TBI. Dr. David Arciniegas discusses Memory Is Not a Single Thing.

So when we talk about memory, one of the things that's important to remember is, memory's not a single thing. Memory has a number of stages. One is learning. The way we get information. Whether that's seeing it or hearing it or feeling it, all of those are modes of learning, if you will. Once information is presented, the brain then needs to represent it, to figure out, well, what is that pattern of seeing or hearing or feeling or combinations of those things?

And begin to commit it to those structures in the brain that help us make sense of it. Once that's been done – we call that process encoding – that pattern becomes, to use the language of the neuroscientists, consolidated, meaning it goes from simply being represented and encoded – a picture, if you will, in the brain of what it is – to something that becomes there long-term.

That network is available to be activated again at some point in the future. All of that would be the initial process of learning new information and beginning to lay down a memory. Later on, with that network having been consolidated, made stable, your frontal lobes or any part of that network, if it comes online, a sound that is familiar, a sight that is familiar, a feel that is familiar – something that's been in that network from the start, can turn it on. You could also turn it on because you're asked to turn it on and think about it and get that network acting. That, we call memory retrieval. So learning, encoding, consolidation, retrieval.

All different parts of the memory process. Depending on where we are in the brain injury cycle, all of those can be disturbed. So early after brain injury, the problem tends to be learning, one or more of the modes of learning – vision, hearing, feeling, et cetera is compromised by the injury. Or, encoding and consolidation. If you can't pay attention, you're not going to encode.

If you're so confused that you can't actually hold onto information long enough, you're not going to consolidate it. And late after injury, those two processes, encoding and consolidation, may still be impaired, but the real trick is then getting it when you need it. Retrieving it. So laying down new information and then getting it out when you need it become the chronic problems for people with injuries.

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