| MadSci Network: Neuroscience |
Daniel,
This answer turned out to be kind of long, so you may want to print it! I think your topic sentence is a good one. To get some background, and figure out what is going on, though, it needs is to be a bit more specific – I’ll let you know why in a second.
The topic of memory is tremendously complex – we still don’t really know what it is or exactly how it works. Memory involves remembering facts (like what you had for dinner last night or what is the capital of Spain); but it also includes things you learn to do, but don’t necessarily have to think about, like riding a bike. There are also different types of memory for things we see, hear, or read. So, to start off, you need to decide what type of memory you want to test.
Let’s assume you want to test how well a person can remember facts, such as a list of words. Now to address the time of day. I haven’t been able to find a lot of research that looks at how people’s memory changes over the day. I did find two articles (that are listed at the end of this), but they don’t really agree with each other. This is probably because:
a) A lot of different things in your body can be changing over the day, and
b) A lot of different things can affect memory
These two things being the case, just looking at memory over the day might not tell us anything terribly informative; even if we discover memory changes over the course of the day, the next question is Why?!
But this isn’t a problem for people like you and me! We can look at a) and b) together. If we take your topic sentence, and make it a bit more specific, we can start to understand what is going on. The new question would be:
What is something that changes in the body over the length of a day, and how does it affect memory?
First we ask, What are things that could change over the course of the day? We could make a list that it might include:
a) Our brain shape – it could get a little squished as gravity pulls on it all day long.
b) Energy - We may run out of it as the day goes on.
c) Attention - We get sleepy as the day goes on.
d) Chemicals - We may run out of something in our brains, or something may clog it up as the day wears on.
People have found that c) and d) are true, and that they are directly linked. There is a chemical in the brain called Adenosine (you may have heard of it – it’s everywhere, and really important!). As the day wears on, the level of adenosine in your brain increases and increases. This increased adenosine makes you sleepy!
“Ok, ok,” you’re wondering, “where is this all going?” WELL, it turns out that adenosine increases most in the part of the brain that is most directly linked to memory, and that increased adenosine causes memory failure. Putting this all together, we show that adenosine increases during the day, and that increased adenosine hinders memory. This being the case, you can start to make a hypothesis about when people’s memory will be the best!
Interestingly, caffeine, which is in Coke and coffee, blocks adenosine from doing its job. So, as you may know, Coke keeps you from falling asleep. But people have also found that the caffeine in Coke can temporarily improve your memory (perhaps by increasing your level of attention). But an IMPORTANT NOTE is that you shouldn’t drink lots of Coke to improve your memory; caffeine is a drug, and is addictive if you use it a lot. And that is something you absolutely do not want. A little bit of Coke every once in a while is ok, but if you have are having one or two cans every day, that’s not good!! Also, sleep is critical for memory, so trying to stay awake for a long time is actually bad for your memory!
Your second question, asking about how sight and sound affects memory is another HUGE can of worms. I can’t address it right here. One thing that I can quickly say is that if you experience something by both hearing and seeing it, you’ll probably remember it better than if just saw it or just heard it.
I hope this helps! I’ve included some websites and articles that might be of interest.
-Alex
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This news article talks about how caffeine could affect memory: h ttp://news.bbc.co.uk/hi/english/sci/tech/newsid_472000/472473.stm
This is a scientific study of how breakfast and caffeine can affect memory: http://www.biopsychiatry.c om/cofbreak.htm
Some science articles: You’ll probably have to go to a medical school library to find these journals; if there’s no med school library close by, or it doesn’t have these journals, go ask your local librarian about an InterLibrary Loan (ILL).
How memory changes over the day:
Tilley A, Warren P, Retrieval from semantic memory at different times of day. J Exp Psychol Learn Mem Cogn 1983 Oct 9:4 718-24
Testu F, Clarisse R Time-of-day and day-of-week effects on mnemonic performance. Chronobiol Int 1999 Jul 16:4 491- 503
How adenosine increases over the day (note: rats are
more
active at night, so their night is like our day!)
Huston JP, et al, Extracellular adenosine levels in neostriatum and hippocampus during rest and activity periods of rats. Neuroscience 1996 Jul 73:1 99-107
How adenosine causes memory
failure:
Ohno & Watanabe, Working memory failure by
stimulation of hippocampal adenosine A1 receptors in
rats.
Neuroreport 1996 Nov 25 7:18 3013-6