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Fly School

Description:
The processes used by humans to perform certain forms of learning are the same as those in many other species. Even the humble fruit fly is an excellent model of how genes affect our ability to learn.
Transcript:
Genes for Learning The processes used by humans to perform certain forms of learning are the same as those in many other species. Even the humble fruit fly is an excellent model of how genes affect our ability to learn. Conservation of function Because we share so many of our genes, humans and many other species often learn in very similar ways. If study learning in humans, cats, rats, dogs, slugs, and worms, therefore, we can see very similar patterns of results. In the following example we will look at learning in fruit flies. Different types of memories Just like humans, flies have many different types of memory, and some flies are better at remembering than others. Short-term memory tends to last less than an hour. Long-term memory can last for days or even a lifetime. Middle-term memory seems to fall between the two. Different genes affect our ability to form different types of memories. A number of factors determine whether a memory will transfer from long-term memory… Making associations For flies, a particular smell is often associated with food. This is an association that the fly has to learn. Here we can see a fly in a ‘T’ maze. To the left, our fly can smell OCT; to the right he can smell MCH. Remembering associations: Flies learn to associate a particular smell with a particular outcome (e.g. a food reward) relatively quickly. However, they also forget quickly. Here we have a bunch of flies in a giant T-maze. They learned the association 3 hours ago – click the mouse to see where they go. 50% of our flies are not smart – there is merely a 50% chance of guessing correctly. However, we can make our flies smarter. One factor that determines whether we acquire a memory is the type of training we receive. When humans learn, and when flies learn, we usually adopt one of two strategies – spaced learning and massed learning. Spaced training is training that is spread over a number of sessions. Mary, any ideas about how we should animate this? Massed training is concentrated on a single session – in other words it is cramming. Mary, any ideas about how we should animate The flies that underwent spaced training performed significantly better than the massed training group (those flies that had crammed). This is just as true for humans as it is for flies. So the lesson here is – DO NOT CRAM! But what makes cramming such a bad strategy? The answer is that these different strategies have different effects on how your brain works. When we learn an association, a series of molecular interactions result in the activation of CREB proteins. CREB proteins are transcription factors, which means they can turn on and off a number of genes in the body, some of which are involved in forming long term memory. This means that CREB proteins can effectively turn on and off long-term memory formation. These memory genes work by strengthening the synaptic connections between two neurons. If they remain active for long enough, the synapses will undergo a permanent change. The synapse gets bigger – a long term memory will have formed! The effect of CREB activators decays over time. If we learn in one block (i.e. if we cram), this decline is never interrupted. If we learn in spaced intervals, however, CREB is repeatedly activated, we can stall the decline. This means that the memory genes stay active longer, which eventually increases the likelihood of a long-term memory forming. Let’s return to the three groups of flies we witnessed earlier. The flies with massed training have failed to form a long term memory. The flies with the spaced training formed a memory that may last their entire life. This is entirely due to the protein synthesis in their brains. The same is true in humans – for long-term learning, it is better to rehearse frequently rather than have one burst of cramming. We can also turn this model on its head. Our third group of flies have been injected with CREB activators. These perform equally as well with massed or spaced training. This is because they are able to lay down long-term instantly. They are so good, in fact, that they are able to lay down long-term memories after only one training session. In other words, they have a photographic memory. It is a very real possibility that in the very near future we may be able to take a pill to enable us to develop photographic memories. There are a number of ethical arguments why such a drug should or should not be made available to the general public.
Keywords:
drosophila, t-maze, maze, fruit flies, fruit fly, fly, flies, ltm, stm, long term memory, short term memory, learning, memory, electric shock, shock, training, experiment, tully, dubnau,
Creative Commons License This work by Cold Spring Harbor Laboratory is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

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