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In a recent news report, I talked about how walking through doorways creates event boundaries, requiring us to update our awareness of current events and making information about the previous location less available. I commented that we should be aware of the consequences of event boundaries for our memory, and how these contextual factors are important elements of our filing system. I want to talk a bit more about that.
I’ve always been interested in the body’s clocks — and one of the most interesting things is that it is clocks, in the plural. It appears the main clock is located in a part of the brain structure called the hypothalamus (a very important structure in the brain, although not one of much importance to learning and memory). The part of the hypothalamus that regulates time is called the suprachiasmatic nuclei. These cells contain genes that switch on, off, and on again over a 24-hour period, and send electrical pulses and hormones through the body. This is the body’s master clock.
What is it?
Frontotemporal dementia is a disorder of the frontal lobes and includes what was known as primary progressive aphasia. Although it occurs far less often than Alzheimer's disease, among dementia sufferers younger than 65 it is estimated to occur at about the same rate. In other words, frontotemporal dementia is, unlike the most common dementias, not a disorder of age. Most sufferers become symptomatic in their 50s and 60s.
Does photographic memory exist?
"Photographic" or eidetic memory is said to occur in some 8% of children, but almost all of these grow out of it. The phenomenon is extremely rare in adults, and indeed the very existence of photographic memory is still somewhat contentious. However, it may be that particular brain abnormalities can lead to ways of processing information that are dramatically different from the normal (see the case of Kim Peek).
What is a tip-of-the-tongue experience?
The tip-of-the-tongue experience (TOT) is characterized by being able to retrieve quite a lot of information about the target word without being able to retrieve the word itself. You know the meaning of the word. You may know how many syllables the word has, or its initial sound or letter. But you can’t retrieve it all. The experience is coupled with a strong feeling (this is the frustrating part) that you know the word, and that it is hovering on the edges of your thought.
Most mnemonic strategies are based on imagery. There is no doubt that imagery can be an effective tool, but there is nothing particularly special about imagery. The advantage of imagery is that it provides an easy way of connecting information that is not otherwise readily connected. However, providing verbal links can be equally effective.
I don’t often talk about motor or skill memory — that is, the memory we use when we type or drive a car or play the piano. It’s one of the more mysterious domains of memory. We all know, of course, that this is a particularly durable kind of memory. It’s like riding a bicycle, we say — meaning that it’s something we’re not likely to have forgotten, something that will come back to us very readily, even if it’s been a very long time since we last used the skill.
Humans have a long tradition of holding genes responsible for individual differences in behavior (of course, we called it "blood", then, or "family"). In the 20th century, a counter-belief arose: that it was all down to environment, to upbringing. In more recent decades, we have become increasingly aware of how tightly and complexly genes and environment are entwined.