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Breaking Science

The Breaking Science team come to BBC Radio Five Live to break open this week's science stories.

The Breaking Science team discussed new research that might help our understanding of how we smell:

Kat Arney: They do say a rose by any other name would smell as sweet, but what does make us think that a rose smells nice but my feet smell bad? My feet don’t smell that bad. But until now scientists have known relatively little about how the smelly molecules, known as odorant molecules, are recognised by the receptors in our noses. But new research by Harumi Saito published in the journal Science Signalling this week could shed some light on this mystery.

Chris Smith: So come on then, tell us why does a rose to me smell like a rose and your feet smell, well let’s not go there.

Kat Arney: Well our sense of smell is an amazing thing and our noses have hundreds of olfactory receptors, each of which can pick up a different smelly molecule and this then sends a signal into the brain which gets interpreted as a smell. But we only know around about 50 of these smelly molecules and that somewhat limits our understanding of the whole system.

Chris Smith: So what are the researchers actually doing in this study to try and home in on what’s going on?

Kat Arney: Well they used a technique called high throughput screening which allowed them to carry out many, many experiments in a short time, and this allowed them to test 93 different odorants, these are the smelly molecules, against a panel of 464 different olfactory receptors, and they picked up 52 specific odorants that activate mouse receptors and the screen pulled out 10 new odorants that activate human receptors.

Smelling a flower.
[image © copyright Jupiterimages]

So this has, you know, made a big increase on what we know about the number of specific molecules that interact with the smell receptors. And the scientists used the knowledge from their screen to then develop a computer model that can help to predict what kind of odorant molecules might fit with different olfactory receptors.

Now it’s probably possible to look at a whole range of smelly chemicals and try and predict which olfactory receptors they might bind to. So this is basically going to speed up the process of research in this area so scientists will have better ideas of which routes to follow rather than just taking shots in the dark.

Chris Smith: It’s interesting because before Christmas I spoke with a perfumer who makes smells for a living, nice smells, and he had the chemical equivalent of synaesthesia, he could imagine a smell and see the molecule in his mind’s eye that would smell like that, so I guess he’d be very interested in a function or a model like that.

Kat Arney: Absolutely. Fascinating.

Listen to the whole programme, originally broadcast on BBC Radio Five Live, February 2009

Blogging about

Breaking Science

The Breaking Science team come to BBC Radio Five Live to break open this week's science stories.

In this extract from episode six of Breaking Science, Doctor Chris Smith and Helen Scales discuss a scientific development which might, one day, lead to the ability to ‘zap’ memories

Helen Scales: Have you seen a film called The Eternal Sunshine of the Spotless Mind? I quite enjoyed it, actually.

Chris Smith: I haven’t. Who’s in it?

Helen Scales: Jim Carey and Kate Winslet, and what happens is she wants to have the memories of an ex-boyfriend taken out of her brain. But,  this kind of fantastical idea might not be confined to the realm of make-believe, because one day this could be a human reality. A team of scientists, led by Joe Tsien from the Brain & Behaviour Discovery Institute at the Medical College of Georgia in the States, have developed a way of rapidly and specifically erasing memories from mice.

The study is in this week’s edition of the journal Neuron, and it revolves around an enzyme called calcium/calmodulin-dependent protein kinase II. A big mouthful but otherwise known as CaMKII, and this has been linked to many different aspects of learning and memory. And they used mice that have actually been genetically modified to have an over-expression of this CaMKII gene, but they also were able to turn it on and off for specific lengths of time, by injecting a specific inhibitor molecule into the brains of these mice.

Chris Smith: So what exactly did they do in this study, and how did they prove that they were able to erase these memories?

Helen Scales: They took these mice, and they did various different things to them, but one of the main things was they gave them a shock. They put them in containers and put a really loud noise in them, and then later on you can look and see if that mouse has actually remembered that shock and that fear by something called the freezing response. You can put them back in the same container, and if they stop and don’t move, except for breathing, then that gives you the idea that they’ve actually remembered that shock from before.

Chris Smith: And they’re frozen because they’re anticipating it might be going to happen again?

A mouse sits on top of a computer mouse.

Helen Scales: Exactly, and so what the scientists did was having exposed these mice previously to that fear, to that shock, they put them back into the container, up to a month later, and then they turned this gene back on again so that what they think actually is linked to the erasure of that memory. It turned out, by doing that, the mice didn’t actually freeze so much. They didn’t freeze, they didn’t remember that fear memory from before.

Crucially, it was at the point of recall that they were doing this, switching on and off of the gene, and by doing that, it only affected that specific memory that they were trying to remember. They were in that box thinking ‘you know, I know this, I’ve been here before and I’ve been shocked before, something about this I remember’, but by putting the gene on at that exact point, that’s the only memory that’s affected. It leaves all the other ones alone.

Chris Smith: And you can see why that would be really helpful, because there are lots of human conditions like post traumatic stress disorder where people remember certain memories too well and they experience all the stress that goes with it. So if you could selectively abolish a memory, in that way, that could be therapeutically very useful?

Helen Scales: It is the exactly sort of thing they’re looking to apply this to, but Tsien and his colleagues are really eager to point out this is very early stage and you won’t be seeing memory-wiping pills on pharmacy shelves any time soon.

Chris Smith: Well hopefully people won’t erase their memory of what you’ve just told them - fingers crossed.

Listen to the full episode of Breaking Science - originally broadcast October 2008

What is MRI?

Magnetic Resonance imaging (or MRI as it is known) is one of the most amazing developments in medicine of the 20th century. It relies on the fact that we have lots and lots of hydrogen atoms in our bodies and that the magnetic behaviour of the nuclei of those atoms depends ever so slightly on the environment of the atom – in other words whether it is a hydrogen atom in fat, or in water, or in brain tissue, and so on.

To do MRI it is essential to place the patient in a strong magnetic field. This is best created in the type of long tube that you saw Jem and Dallas going into in episode 3 of Bang Goes The Theory.

Patient going into an MRI scanner. [Image of Signa HDx scanner, courtesy of GE Healthcare]

Once the subject is in the bore of the magnet, additional complicated sequences of smaller but rapidly varying magnetic fields are created by currents in coils of wire around the bore of the machine.

As the currents in the coils change the coils move, and this creates the noise that one can hear inside the scanner. These varying magnetic fields are used to create an image of the part of the body under investigation.

MRI is really effective for imaging soft tissue and has a wide variety of uses. One of the best uses is for diagnosing joint problems - as in this image of a knee.

MRI scans are excellent for showing up soft tissue such as ligaments and tendons in joints. This is an MRI scan of a knee. [Image courtesy of GE Healthcare]

What is the difference between MRI and fMRI?

Most of the images created in hospitals using MRI show structural features of the body, but it is also possible to show some information about the oxygen consumption of tissues as well – this is known as functional MRI, or fMRI for short. When the brain is working it needs a good supply of oxygen. The oxygen is carried in the blood in the form of a substance called oxyhaemaglobin. When the oxygen has been used up the remaining substance is called deoxyhaemaglobin.

Rather fortunately for brain researchers, oxyhaemaglobin and dexyhaemaglobin have different magnetic properties, so it is possible to see which parts of the brain are using more oxygen – or working harder.

And here’s a strange fact: one might think that there would then be more deoxyhaemoglobin in the regions of the brain that are working hardest but in fact the opposite is true!

The active regions of the brain need more oxygen, so the blood supply is increased and is increased by so much that there is extra oxyhaemaglobin in the active parts of the brain.

The sequences used in fMRI will pick up this extra blood supply and therefore give us a picture of the active regions of the brain. This technique is called Blood Oxygen Level Dependence, or BOLD, and is widely used by researchers such as those at the MRC, who are looking at the ways our brains carry out certain functions. Hence the lovely images of Jem’s brain solving problems better than Dallas’! .

An fMRI scan showing with areas of increased activity highlighted. [Image courtesy of GE Healthcare]

Find out more

Daniel Bor explains neuroimaging, and what it might tell us about the mind

James Bruce on fluorescence imaging

Study Understanding Health with The Open University