Read more: 鈥�Instant Expert: Memory鈥�
All too often, our memory can fail us. We all forget important facts from time to time, but in the most serious forms of amnesia people may have no concept of their recent past whatsoever. Understanding memory failings can help researchers work out how we form and retain memories.
Why do we forget?
Any effective memory device needs to do three things well: encode information in a storable form, retain that information faithfully and enable it to be accessed at a later point. A failure in any of these components leads us to forget.
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Distraction or reduced attention can cause a memory failure at the encoding stage, while a problem in storage 鈥� following brain injury, for example 鈥� can cause us to lose the encoded information. Memories can also 鈥渇ade鈥� and become less distinctive if the storage of other memories interferes with them, perhaps because they are stored in overlapping neural assemblies.
Often, memory failures occur when we try to retrieve information, leading to the feeling that a fact is 鈥渙n the tip of my tongue鈥�. For example, it can be intensely frustrating to forget someone鈥檚 name at a party, only to remember it a few hours later. This problem might be because the brain鈥檚 search algorithms aren鈥檛 perfect, and it may sometimes have trouble distinguishing the right signals from other neural noise.
Despite its drawbacks, forgetting can also be useful and adaptive. Other things being equal, we tend to remember things that are salient and non-trivial; for example, information that is potentially rewarding or threatening.
Amnesia
The 鈥渁mnesic syndrome鈥� (also known as classical amnesia) is one of the purest forms of memory impairment. It is typically caused by a specific injury either to the hippocampus or to a region deep in the brain called the diencephalon, which appear to be involved in consolidating memories. In the case of patient SJ, whom my colleagues and I have studied, the profound amnesia was due to an apparently very focal lesion of the hippocampus caused by an infection. In the case of the patient known as NA, the damage was caused by an accident in which a fencing foil penetrated his brain via a nostril.
People with this disorder lose their ability to recall events before the brain injury in question, a condition known as retrograde amnesia, and also cannot lay down new memories after the injury 鈥� they have anterograde amnesia. The amnesic syndrome does not affect all forms of memory, however. Knowledge of speech, language and other elements of semantic memory are usually preserved, as is short-term memory. People with the condition can also remember specific skills, such as how to drive, and sometimes master new abilities, even though they typically can鈥檛 remember the events that led them to learn the skill! By contrast, the ability to retain new information over any significant period of time is profoundly affected in people with classical amnesia; they find it almost impossible to learn the name of the person they just met, for instance.
The study of memory impairment has considerably informed our knowledge about how memory operates in the fully functional state. As the influential psychologist Kenneth Craik once said: 鈥淚n any well-made machine one is ignorant of the working of most of the parts鈥� it is only a fault which draws attention to the existence of a mechanism at all.鈥�
Can I improve my memory?
At the moment, none of us can reliably improve the biological hardware involved in memory, though it is comparatively easy to damage it via drug and alcohol abuse or injury. So-called 鈥渟mart drugs鈥� and neurochemical agents claim to improve the functioning of our memory circuits, but although some treatments have been shown to help people with impaired memory due to brain damage or illness, their effects seem to be unreliable and insubstantial in healthy people.
We can ensure that we make the best possible use of our memory by living and eating healthily, and by using a range of mnemonics, some of which have been known for thousands of years. Most mnemonics are based on the principles of reduction or elaboration. As the name suggests, a reduction code reduces the information to be remembered (through an acronym like the words Roy G Biv, which helps children to remember the colours of the rainbow). An elaboration code increases the information to be retained, perhaps through a catchy phrase like 鈥淩ichard of York gave battle in vain鈥�, which again is used to remember a rainbow鈥檚 colours. There are some more detailed systems too, like the peg word system. This involves assigning a memorable rhyming word to a number: 鈥渙ne is bun鈥�, 鈥渢wo is shoe鈥�, 鈥渢hree is tree鈥�. A list can then be remembered by linking each item in the sequence to each peg word, through a memorable image.
鈥淲e can make the best use of our memory by living and eating healthily and by using mnemonics鈥�
There are many other ways of increasing your chances of recall, such as actively elaborating or rehearsing information, organising it in a new way, or attempting to explain what you are studying to someone else. Timing your study so that you attempt to remember a piece of information after steadily increasing intervals can also help to lay the foundations for effective long-term recall.
