Here's Looking at You - the Science of Vision

Every single minute, a woman dies from pregnancy related causes somewhere in the world.  That's one statement from the Population Institute in Washington made to highlight World Population Day, held by the United Nations Population fund on the 11th of July.

Global population is growing at a phenomenal rate - It took all of human history until 1830 for world population to reach one billion. The second billion was achieved in 100 years, the third billion in 30 years, the fourth billion in 15 years, and the fifth billion in only 12 years.  Population is predicted to exceed 9 billion by 2050.

We're made very aware of the threats of a changing climate, how rising sea levels could force millions out of their homes, threaten food security and increase conflict, but rising population can only make all of these effects worse.  Larger populations need more land for crops, reducing forest cover, decreasing biodiversity and ecosystem services and actually making climate change worse.

Overpopulation is also at the root of more immediate human problems - poverty, HIV/AIDS, childhood illness, access to drinking water and the effectiveness of vaccination programmes are all made worse by being overpopulated.

World Population day hopes to raise awareness of the issues of overpopulation, especially to governments who are considering ways to save money in the current financial climate.

There's no quick fix for overpopulation, and it's certainly not something we can solve in a single day, but an awareness of the problems and opportunities can help us, and our governments, make the right decision.

Investments in women's education, family planning, public health and other social services can make a difference, and should not be allowed to suffer because of the global financial crisis.  Already, developing nations are feeling the consequences of the financial crisis in the west -the credit crunch has affected funding for HIV/AIDS programmes in Africa;  90% of family planning in Uganda relies on overseas funding and half of the funding for healthcare in Africa comes from funding sources in America.  A financial crisis in the west risks becoming a humanitarian crisis in the developing world.

Chris -   Now this week was also Cambridge University's Darwin Festival.  What actually happened was that we've had a full week of events which have been designed to celebrate the 200th anniversary of the birth of Charles Darwin who was actually a Cambridge University student.  Also, it's 150 years since he published arguably one of the most famous books of all time, The Origin of Species which effectively rewrote our understanding of the world of biology around us.  But one event that took place as part of the festival and really leapt out was a Canadian hip-hop artist - he's actually an erstwhile medieval historian - His name's Baba Brinkman, and he unveiled his answer to Darwin which is his Rap Guide to Evolution and he spoke to David Fisher all about it.

David -   The week here at Cambridge has seen mostly older scholarly types in panel discussions or alone at the lectern, analysing, speculating, debating, and theorizing over every nuance of Charlie Darwin's existence.  So, for a summary of the week, here's rap artist Baba Brinkman who covers every angle of every session in his hip-hop show, The Rap Guide to Evolution.

Baba -   So whatcha know about natural selection?

Go ahead and ask a question and see where the answer gets you.

Try the impassive aggressive or try smashing heads in and see which tactic brings your plans to fruition.

And if you have an explanation in mind then you're wasting your time coz the best watchmaker is blind.

It takes a certain base kind of impatient mind to explain away nature with intelligent design.

But the truth shall set you free from those useless superstitious beliefs of the literal Adam and Eve and that Edenic myth 'coz their family tree is showing some genetic drift.

Take it from this bald headed non-celibate monk with the lyrical equivalent of an elephant's trunk. 

It's time to elevate your mind's state and celebrate your kinship with the primates. 

The weak and the strong, who got it going on.  We lived in the dark for so long. 

The weak and the strong, Darwin got it going on.  Creationism is dead wrong.  Tell them Dawkins...

David Fisher -   This Canadian rapper is no scientist.  His area is medieval literature.  After applying rap to the Canterbury tales, he was approached by a microbial genomist who asked if he could do for Darwin what he did for Chaucer.  Baba read his way through a pile of books on evolutionary biology and out spawned his Darwin show, covering every aspect of the great man's work.  And according to Baba, there's a curious similarity between the creation, sorry, the growth, the evolution of an artistic work and any living thing.

Baba Brinkman -   When I first started writing the show back in January, early drafts of the script sounded a little bit like this: 

Yo!yo!

The origin of species ain't no faeces. 

Dawg, believe me. 

Yeah!

And that was all I think of. 

And then I thought, I thought.  Well, maybe my show needs to get rewritten and sometimes, people ask me how does a show get written? 

Like this, performance, feedback, revision.

And how do I generally develop my lyricism? 

Kind of like this, performance, feedback, revision. 

And how do human beings ever learn to do anything? 

Like this, performance, feedback, revision.

And evolution is kind of just an algorithm, isn't it?

That goes like this, performance, feedback, revision.

So, really the genetic code of very living thing was written like this,

Performance, feedback, revision.

So, the genes are like a text with a thousand pages and revisions occur in the random changes that come from mutations and then when they...

Chris -   That's rap artist Baba Brinkman from Canada who was able to be here in Cambridge touring with his rap, effectively Darwin set to a rap tune.  He was talking to David Fisher who was an honorary member of The Naked Scientists for a week but you'll normally find him at ABC at Radio National in Sydney, Australia.

We've actually got a recording of that entire show and we're going to be publishing it for you as a special podcast on our website later this week.  So, if you check out thenakedscientists.com/podcasts, then you should be able to listen to all of Baba Brinkman's show.

Chris - Indeed, this was the nodulisporium fungus which is an environmental fungus but it produces nodulisporic acid which the paper we reported on last week is scientists making a version of that called nodulisporamide which targets an ion channel which is only present in insects. It's not present in people and it's therefore neurotoxic to insects but because we don't have their ion channel, it's harmless to us. I suppose it's possible that we could do the same thing for other flying insects. The problem is of course, you'd have to dose enormous numbers of people. If you're going to dose enormous numbers of people or something, you might as well give them an anti-malaria drug in the first place. So, I guess that that's one of the criticisms. Isn't it? That if you're going to do something like that, well, might as well treat the disease that's mostly the problem, but it's a good idea and it may be that that's one way to tackle this.Ben - That's very true. If we already had the facility to dose that many people with any medication then, yes, we'd be using anti-malarials, wouldn't we?

Ben -   Now, that's how the eye itself works even in some very unusual circumstances but an eye alone isn't much use without a brain to interpret what the pictures mean.  It's not fully understood just yet how the brain interprets information from the eyes.  There have been some very great advances recently.  A Japanese team could predict what letter was being read just by looking at brain activity alone for example.  But we do still have a long way to go.  Now one problem is the issue of attention.  How does the brain know what's important in any given view?  Professor Alex Thiele is from Newcastle University where he's trying to work this out.

Alex -   I'm interested in how attention works and particularly in a mechanistic analysis of attention.  So we kind of know what attention does to various aspects of our everyday perception but we don't really understand how it is implemented in the brain.  So I'm looking at the brain chemicals that mediate various aspects of attention and I'm also looking at how neurons are affected by these brain chemicals and how neurons communicate and how neurons interact during attention.  And one current view is that synchronous or oscillatory activity between groups of neurons is a very important aspect of attentional processing and I'm looking at those aspects, how different areas synchronize their activity and what these neuron modulators or neurotransmitters these brain chemicals, what role they play in this synchronicity.

Ben -   Attention is a word that we use in common language a lot.  We pay attention to a television program we're interested in or we pay attention to the weather broadcast for example to know what's coming up.  Does it mean the same thing for you as it would do in common parlance?

Alex -   In a way it does, and at the same time it doesn't.  I think until a few years ago, attention was used in a fairly restrictive manner but most people now start to argue that attention really is just the process that allows us to use task relevant information appropriately.  So if we are involved in a certain task, then we have to pay attention to the aspects that allow us to do the task. In tennis its one specific set of aspects looking at the ball making sure our movements are right.  If we watch the weather forecast, it's a different task.  So attention really allows task relevant information to be processed adequately, and non-task relevant information to be excluded from interference.

Ben -   So, how do we know what's going on in the brain while we're diverting our attention to one particular thing?

Alex -   We know that neurons that process this particular aspect increase their activity so to speak, they shout louder.  We also know that in, certainly in certain areas, neurons are synchronous and synchronous activity is kind of like clapping, a clapping audience that is synchronous where everyone claps at the same time makes the whole theater be much more noisy, much louder and that's what synchronicity in the brain also does in a way so we know the neuron shout louder.  We know they act all together that then make sure that basically, they are above the noise and that aspects of the visual world reach consciousness.

Ben -   The brain is a phenomenally complicated and wonderful thing but it does have a tendency to go wrong.  Are there processes where this attention can break down?

Alex -   We are all distractible.  There are diseases where attention doesn't work properly anymore.  I mean Alzheimer's disease is one example, late stages of Parkinson's, certain stroke types show that attention doesn't work properly. In everyday life it would be more distractibility, that we can't focus properly, but how this actually happens in everyday life.  I don't think people understand properly yet.

Ben -   And one of the things you're looking at is brain chemistry.  How do the different chemicals in the brain translate to paying attention?

Alex -   Well we know very little about that.  We know that certain chemicals which are called modulators like acetylcholine or dopamine or an adrenaline play some role in attention but exactly what role they play is still very little researched.  I mean we recently were able to demonstrate for one particular part of the brain, the primary visual cortex, that acetylcholine mediates its effect through a specific receptor type but that is just in this one particular area.  All the other areas are still, its unknown how acetylcholine works there.  It is also at least to a large extent unknown how for example dopamine contributes to attention in a very detailed and mechanistic manner.  And then there are the more traditional neurotransmitters like glutamate which acts through certain receptors again where specific receptor type may or may not contribute to attention.  So we're just about to begin to understand how these different brain chemicals contribute to various aspects of attention and also to what aspects of attention because as I've said at the outset, attention is a complex phenomenon.  It allows task relevant information to be processed and different neurotransmitters may allow different types of task relevant information to be processed accurately so it's, and well in a way fortunately, but at the same time unfortunately, a rather complicated interplay of all these brain chemicals.

Ben -   So there's so much still to learn.  This is really exciting stuff.  He was a wonderful chap to talk to and really it is an interesting question of what does attention mean to me and what does it mean to him and what it means to other people.  So there you go, that is Professor Alex Thiele from Newcastle University, explaining how the brain relies on coordinated nerve activity and a whole cocktail of chemicals in order to pay best attention to the world, depending on exactly what you're doing at the time.

Ben -   The only visual information we have about the outside world, thinking about it objectively is patterns of light that fall on our eyes.  We've just heard how the brain can interpret that light differently depending on what you're doing at the time.  But actually, all this means that we don't really see what's really there, the context itself is important.  To find out why, Beau Lotto from the University College London is looking at optical illusions, and finding out how bees see the world.  Meera Senthilingam went along to have her eyes fooled...

Beau -   So what we're looking at is a very well-known, very simple illusion called simultaneous brightness contrast and so we see two small squares and each of those squares is on two different surrounds.

Meera -   Yes.  Looking at this, there are two grey squares.  One's on a darker grey background and one's on a white background and to me now, these two smaller grey squares look like different shades of grey.

Beau -   That's right.  But if you put up a photometer, if you put up a light measurer to them, you would find out that those smaller squares are physically the same.  Their emitting the same amount of light to your eye and yet they look differently bright.  Now most textbooks would say, the reason for this is simply that one is on a light surround and one is on dark surround but that answer can't be right because I can also create an illusion where something on a dark surround looks darker than something on a light surround.  The illusion goes exactly the opposite direction.  So it can't simply be about, it's the lightness and the darkness of the surround that matters.  The argument here is what those relationships meant for your behaviour in the past?

Meera -   So having used all these images and knowing what you know so far, do you know much about the actual physiology and the mechanisms going on in our brains that cause us to see these illusions in this way.

Beau -   Well to understand how we see illusions is to understand how we see generally.  And what this work suggests is that the only way we can understand perception is to quantify our history of experience or with humans, this is very difficult because our history is for the most part lost to us.  But fortunately, to understand something like seeing colour and dealing with the ambiguity of light stimuli, we don't need to work, focus on humans when in fact, we don't even need to focus on mammals.  We can look at insects and in particular, we can look at bumblebees.  So the beautiful thing about bumblebees is that they see colour and we see colour.  Their brain is able to resolve the ambiguity of light stimuli and the wonderful thing about bumblebees as opposed to honeybees is that we can completely control their visual experience which means that we can raise them in an environment where we know everything about the colours that they have seen.  And we can look to see how that experience shapes itself in the architecture of their brain and also the resulting behaviours.

Meera -   So how do you know ago about testing these bees because I just now have an image of you showing lots of illusions to bees.

Beau -   Well in a way we do actually.  So we do that in a space we call the bee matrix.  It's a plexiglass cube that's one meter on all sides and at one end, you have 64 flowers that are lit up from behind and with these flowers, we can control the colour by putting filters behind them and we can train the bees to go to certain colours and not others.  So if they land on the right colour, they get a sugar reward.  If they land at the wrong colour, they get saltwater.  So what we can do is we can train them to go to, for instance, find the blue flower, except the blue flower is now under different colours of light.  So the light coming from the blue flower varies.  So what they have to do is they have to use their relationships between the flowers and the surround in order to figure out which is the cracked one and what we found is that they do that.  They actually encode the colour relationships so they can learn to go to the bluest flower in the array or the yellowest flower in the array.  Now sometimes, a grey flower is the bluest flower if everything else is yellow so it's actually a pretty complex thing that they're doing and then what we can do is we can look to see how those relationships are encoded in the architecture of their brain.  So the brain doesn't do absolutes.  It can't do absolutes.  There's no point in seeing absolutes.  What it does is it encodes relationships and it's actively encoding the relationships that matter.

Meera -   And this is all not just through the training of them from their birth but it actually just goes through the past evolution of the bees and of us humans.

Beau -   That's true so we come into the world with the ability to encode relationships.  When we talk about experience, we don't distinguish between evolutionary history or development or memory.  Basically, they're all different ways of doing the same thing which is to shape the brain according to its trial and history of experience.

Meera -   So you now know this about the bees' behaviour but what are you working on now and next in order to understand just what's going on inside the brain?

Beau -   So what we want to do now is trying to discover how those relationships are actually encoded in the structure of their brain and to do that, we can take little electrodes which are fine, fine wires and stick them into the brain of the bee and we can listen to their brain cells while they see the history of their own visual experience.  The reason why we do it in humans and bumblebees is that these are very, very different types of brains taking the same kind of information coming up with the same solution.  And if we can understand how both types of brains do it, then we can understand the principle that is relevant to both.

Chris - No. People did think but it happens too quickly. The photic sneeze reflex to recap is when you go out on a sunny day, bright light comes to you and you suddenly feel this irresistible urge to sneeze often multiple times. About one person in five is affected, tends to run in families, and it seems to be a neurological phenomenon. It's not a tear tickling your nose phenomenon because you tend to sneeze quicker than your eyes water so people have sort of written off that theory unfortunately. So we think it's more the same thing that makes your pupil get smaller and you blink in response to bright light, probably the same bit of the brain that's doing that is also crossing over into the sneezing center a little bit and triggering both reflexes.Ben - So it's wiring rather than plumbing?Chris - Absolutely!