An Introduction to Memory
“What was the name of that song? The one that kind of has that bass at the start, then the guitar riff? It’s on the tip of my tongue…what’s the name?” Sound familiar?
Our propensity to forget facts shows how poor our memory can be. Yet stick a catchy tune, or a rhyme, and the lyrics seem to stay with us – why is that? Why do some people remember words to a song better than others? Or why do some people remember the tune to a song better than others? It’s all about our memory. It’s how we remember that shapes us; and, unfortunately, the loss of memory can do that too.
Memory, without getting too eloquent, often forms the basis of our everyday interactions. This covers the encoding, storage, and retrieval of information. For example, imagine you are walking through the woods, and you spot a green snake. Our previous interaction with a snake may have occurred when you were nine, and it bit you. You remember this, and so, whenever you now see something similar, you decide to move away. This is a simplistic example, but the model can be applied in many situations. As a result, this ‘memory model’ can map out how our brains function, when it comes to memory. However, in psychology, there are many variations of a ‘memory model’; this has been a topic of debate for many decades.
MODELS OF MEMORY
Early models formed the basis for further research. First, the multi-store model (MSM), established by Atkinson and Shiffrin in 1968, proposed three main components: a sensory, short-term, and long-term store, sequentially interlinked with the other. However, the MSM had criticisms – primarily, that the model was over-simplified. According to the positions of short-term (STM) and long-term memory (LTM), STM impairment would lead to a dysfunction of LTM. However, patients with lesions could have an impaired STM, yet a preserved LTM. While it supports multiple systems, it shows MSM failing in its sequential idea. As a result, an improved model was proposed by Baddeley and Hitch in 1974: here, the term ‘working memory’ was more prominently used. This involved separate loops for auditory and visual memory, later combined with an episodic buffer to transition information.
Additionally, there is a question as to whether memory is a unitary construct: that is to mean, are there domain-specific subcomponents? Or do all their functions fall under the same cloth? The models, proposed before, are regarded as multiple-system models – conversely, unitary models have been suggested as well. Nairne’s 1990 model described the components of memory as a continuous stream; and, based on correct cues, information is recalled. The model accounts for various phenomena, such as similar information displacing those previously-learned, but relies heavily on interference theory to support imperfect memory recall. Interference theory suggests events, occurring before or after learning, impede the correct retrieval of memories. However, there are several faults with unitary models: the biggest flaw is that none, so far, align with neuroanatomical evidence. For example, one model implies that memories have constantly-shifting locations within the brain, while another describes information floating within unspecified structures. Mental events cannot be detected in the brain with our current imaging techniques. Thus, both unitary models can only describe their mechanisms from this perspective. Current scientific evidence supports neither and subsequently, it can be suggested that unitary models provide an oversimplification and may be anatomically incorrect.
EVIDENCE OF MEMORY
The simplest answer to what is involved with memory involves experiments – and a common pathway would be to focus on lesion studies: through loss of function, examining behaviour, one can infer function through neural correlates, thus examining the biology. Our long-term memory can be broken down into further subsets: we have explicit and implicit memory. Explicit memory is the recollection of facts and figures: what can be explained. Meanwhile, implicit memory deals with unconscious actions, such as riding a bike: we know we can ride a bike, but we cannot explain how or why – we just do. If the diagram of LTM is correct – that it can be divided into subsets – there must be evidence; the case study of Kent Cochrane, commonly known as KC, provides us with such evidence. They found that impairment of the medial temporal lobe leads to anterograde amnesia: the inability to form new memories.
"Implicit memory deals with unconscious actions, such as riding a bike: we know we can ride a bike, but we cannot explain how or why – we just do."
This is where the study of memory gets tricky; a more in-depth analysis is featured in another article, but the premise is as follows: we know the hippocampus is involved with memory formation. But where are our memories stored? They are not exclusively stored in the hippocampus – studies have shown removal of the hippocampus does not lead to complete loss of memory, but certain types of memory affected. Additionally, what if our memory models are incorrect? After all, there is a surprising wealth of evidence to say so. Should we turn our attempts to a different method of studying memory? These questions are still being discussed, showing how complex and challenging the study of memory is.
Our idea of memory is constantly changing: new evidence can sometimes throw previous models into question. Our job, as scientists, is to review the evidence, and decide whether it actually poses a significant threat to models of memory. A further scenario to think about: suppose you were retelling your friends what happened when you were in a car accident one time – the car smashed into the rear, and luckily no glass got broken. However, your friend, who was with you during that accident, doesn’t describe the same picture: there was some glass shattering, but the cars only bumped into each other. Which one of you is correct? And even so, how could one of you describe so inaccurately? Is your memory failing you, or is it something more than that?
Atkinson, R.C., and Shiffrin, R.M. (1968). Chapter: Human memory: A proposed system and its control processes. In Spence, K.W. and Spence, J.T. (Eds.), The psychology of learning and motivation, 2: 89-195. New York: Academic Press.
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Karlsen, P.J., Allen, R.J., Baddeley, A.D., and Hitch, G.J. (2010). Binding across space and time in visual working memory. Mem Cognit. 38(3): 292-303. doi: 10.3758/MC.38.3.292.
Nairne, J.S. (1990). A feature model of immediate memory. Mem Cognit. 18(3): 251-269.
Paulesu, E., Frith, C.D., and Frackowiak, R.S. (1993). The neural correlates of the verbal component of working memory. Nature, 362(6418): 342-345Tulving, E. (1998). Study of memory - processes and systems. In Foster J.K. & Jelicic M. (Eds.), Memory: Systems, Process, or Function? 11-30. Oxford: Oxford University Press.