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0:00:00 > 0:00:02- Subtitles- - Subtitles
0:00:02 > 0:00:05- Every single second of every day...
0:00:05 > 0:00:09- ..our senses gather information - about our environment.
0:00:09 > 0:00:14- The senses connect us - to our surroundings.
0:00:14 > 0:00:17- I'm Dr Anwen Rees, - a Physiology lecturer...
0:00:17 > 0:00:20- ..at Cardiff Metropolitan - University.
0:00:21 > 0:00:27- I'm Dr Katie Hemer, a Bioarchaeology - specialist at Sheffield University.
0:00:27 > 0:00:31- We will look at the way the brain - uses information...
0:00:31 > 0:00:34- ..to create - a unique picture of the world.
0:00:35 > 0:00:39- We will look at familiar - and unfamiliar senses...
0:00:39 > 0:00:41- ..and how they collaborate.
0:00:41 > 0:00:43- And how to trick them.
0:00:49 > 0:00:53- SIGHT
0:00:56 > 0:01:00- More than any other sense, - we see the world.
0:01:01 > 0:01:06- A glance tells us the size, shape, - colour and proximity of everything.
0:01:06 > 0:01:10- It also identifies objects - and how fast they're moving.
0:01:15 > 0:01:19- How does the sight system - combine all this information...
0:01:19 > 0:01:22- ..to create a snapshot - of our surroundings?
0:01:24 > 0:01:28- Should we believe everything we see?
0:01:32 > 0:01:34- How do we see the world?
0:01:34 > 0:01:38- Light bounces off an object - and enters the eye via the pupil.
0:01:38 > 0:01:42- Muscles in the iris, - the coloured area of the eye...
0:01:42 > 0:01:45- ..regulates that light.
0:01:46 > 0:01:50- Light passes through a clear lens - whose thickness can adjust...
0:01:51 > 0:01:55- ..to allow you to focus on distant - objects and near objects alike.
0:01:56 > 0:01:58- The lens focuses light - onto the retina.
0:02:00 > 0:02:04- There are 100 million cells - called rods on the retina.
0:02:04 > 0:02:07- They allow us - to see black, white and grey.
0:02:07 > 0:02:11- There are also 7 million cones - which allow us to see colour.
0:02:11 > 0:02:13- The three types of cones...
0:02:14 > 0:02:18- ..are sensitive to primary colours - - red, blue and green.
0:02:18 > 0:02:22- They combine to allow us - to see millions of colours.
0:02:22 > 0:02:25- The retina converts light - into electrical events.
0:02:26 > 0:02:30- They travel down the optic nerve - to the visual cortex, in the brain.
0:02:30 > 0:02:35- Pictures reach the brain upside-down - but the brain flips them around.
0:02:38 > 0:02:41- Most of us have had an eye test - in the past.
0:02:43 > 0:02:46- Almost 70% of the UK population - wears spectacles.
0:02:46 > 0:02:50- What happens to the eyes - to make us have to do this?
0:02:50 > 0:02:54- And why is it so important - to have regular eye tests?
0:02:58 > 0:03:00- I met Dr Norma Davies...
0:03:01 > 0:03:05- ..at the School Of Optometry - & Vision Sciences, Cardiff.
0:03:05 > 0:03:10- I want you to put your eye - close to that circle.
0:03:12 > 0:03:16- Norma will test my eyes - to see how healthy they are.
0:03:16 > 0:03:18- X, O, A, T.
0:03:24 > 0:03:27- You ran a lot of tests - on my eyes today.
0:03:27 > 0:03:29- Can we go through them, please?
0:03:30 > 0:03:34- First, we used the optomap, - the retinal imaging device.
0:03:35 > 0:03:39- The green and orange background here - is the retina.
0:03:40 > 0:03:42- The yellow area - is the optic nerve...
0:03:43 > 0:03:45- ..which carries messages - to the brain.
0:03:49 > 0:03:50- That's the macula.
0:03:50 > 0:03:52- Is the macula important?
0:03:52 > 0:03:54- Is the macula important?- - Yes.
0:03:55 > 0:03:57- The macula is the area of the eye...
0:03:57 > 0:04:02- ..where the resolution of what - you see is higher than elsewhere.
0:04:02 > 0:04:07- If you damage the macula, - it has a huge impact on your sight.
0:04:09 > 0:04:13- Next, the standard eye test - with those silly spectacles!
0:04:14 > 0:04:16- What were you looking for there?
0:04:16 > 0:04:21- We put different lenses in them - - stronger and weaker.
0:04:22 > 0:04:26- The aim was to find the best point - for you to see the bottom line.
0:04:27 > 0:04:29- I asked you if you saw better...
0:04:29 > 0:04:33- ..with the first or second side - of the lens...
0:04:33 > 0:04:35- ..to check for astigmatism.
0:04:36 > 0:04:41- Katie, I'd like you to read - the letters, one eye at a time.
0:04:41 > 0:04:43- I can see the top letter.
0:04:45 > 0:04:46- I think it's a T.
0:04:47 > 0:04:48- What is 20/20 vision?
0:04:48 > 0:04:50- On the chart we used...
0:04:51 > 0:04:56- ..the second line from the bottom - denotes 20/20 vision.
0:04:56 > 0:05:01- Americans call it 20/20. - We call it 6/6 vision in Britain.
0:05:01 > 0:05:05- That's what is classed - as normal vision.
0:05:05 > 0:05:08- X, O, A, T, Y.
0:05:08 > 0:05:13- You read the bottom line, - so your sight is better than normal.
0:05:13 > 0:05:14- With my glasses!
0:05:14 > 0:05:15- With my glasses!- - Yes.
0:05:15 > 0:05:17- Place your chin here.
0:05:17 > 0:05:21- I didn't enjoy the next test, - which was for glaucoma.
0:05:23 > 0:05:27- Yes, the one where we blow - a puff of air into your eye.
0:05:28 > 0:05:30- Well done. You had a shock there!
0:05:30 > 0:05:32- Yes. I didn't like it.
0:05:32 > 0:05:35- It gives us a reading - of the pressure in your eye.
0:05:36 > 0:05:39- Glaucoma is a disease - which affects the optic nerve.
0:05:40 > 0:05:45- You cannot regain any sight - lost as a result of glaucoma.
0:05:46 > 0:05:49- There's more to an eye test - than checking sight.
0:05:50 > 0:05:51- Yes, most definitely.
0:05:52 > 0:05:55- For example, we can detect glaucoma - at an early stage.
0:05:57 > 0:06:01- Diabetes, high blood pressure - and high cholesterol...
0:06:01 > 0:06:07- ..can show up in the eyes of people - who had no idea anything was amiss.
0:06:08 > 0:06:12- There's much more to it - than a new pair of spectacles.
0:06:13 > 0:06:14- Do my eyes look healthy?
0:06:14 > 0:06:16- Do my eyes look healthy?- - Yes. They look great.
0:06:21 > 0:06:24- Does our sight - differ from that of animals?
0:06:25 > 0:06:29- Zoologist, Dr Gethin Evans, - invited me to see for myself.
0:06:30 > 0:06:32- WHISTLING
0:06:38 > 0:06:41- Gethin, this is a familiar sight - in Wales.
0:06:41 > 0:06:45- What can these animals tell us - about our sight?
0:06:45 > 0:06:49- The first obvious thing with sheep - is the position of the eyes.
0:06:49 > 0:06:52- They're on the side of the head.
0:06:52 > 0:06:57- That's because sheep evolved from - an animal which was hunted...
0:06:57 > 0:07:01- ..so better peripheral vision - was advantageous to them.
0:07:01 > 0:07:07- Canine and human eyes are at the - front of the head, facing forward.
0:07:08 > 0:07:12- We can see what's in front of us, - which is ideal for hunting.
0:07:14 > 0:07:18- Is it true that dogs only see - in black and white?
0:07:18 > 0:07:23- No. Dogs do have colour vision - but it's different from ours.
0:07:23 > 0:07:26- There are three types of cone - in human eyes.
0:07:26 > 0:07:29- They allow us - to see red, blue and green.
0:07:29 > 0:07:33- There are only two types of cone - in canine eyes.
0:07:33 > 0:07:36- They see colours - like brown, blue and yellow...
0:07:36 > 0:07:40- ..but they don't see red - in the same way as humans.
0:07:42 > 0:07:44- What about other animals?
0:07:44 > 0:07:48- There's a wide variety of receptors - in animals' eyes.
0:07:48 > 0:07:52- Birds have four different - colour receptors.
0:07:52 > 0:07:55- Ultraviolet light - is visible to them, unlike us.
0:07:56 > 0:08:00- The mantis shrimp views the world - in 12 primary colours.
0:08:00 > 0:08:02- Nine more than humans.
0:08:02 > 0:08:06- Why do animals need to see - different colours from us?
0:08:06 > 0:08:10- It allows them - to see more of their surroundings.
0:08:10 > 0:08:14- The bee goes from flower to flower - collecting pollen.
0:08:14 > 0:08:19- Several flowers have ultraviolet - patterns on leaves and flowers...
0:08:19 > 0:08:24- ..which act like airport landing - strips, guiding bees to the pollen.
0:08:25 > 0:08:28- Are there any strange eyes - in nature?
0:08:29 > 0:08:31- Yes - our eyes! Mammals' eyes.
0:08:31 > 0:08:33- We all have a blind spot.
0:08:33 > 0:08:37- Animals such as the octopus - don't have a blind spot...
0:08:37 > 0:08:41- ..because their eyes - evolved in a different way...
0:08:41 > 0:08:44- ..but the nerves - are behind the retina.
0:08:44 > 0:08:49- An octopus's eyes are better, - in some respects, than our eyes...
0:08:49 > 0:08:52- ..because they don't have - a blind spot.
0:09:06 > 0:09:09- We're all used to wearing these - in cinemas...
0:09:09 > 0:09:12- ..to allow us to see images - on a flat screen in 3D.
0:09:13 > 0:09:16- How do we see the world around us - in three dimensions?
0:09:20 > 0:09:23- When we look at something, - our eyes cross.
0:09:23 > 0:09:26- Because our eyes - are two inches apart...
0:09:26 > 0:09:30- ..the brain receives - two slightly different pictures.
0:09:30 > 0:09:33- One from the left eye - and one from the right eye.
0:09:34 > 0:09:37- The brain combines the two - into one picture...
0:09:37 > 0:09:40- ..and through this, - it measures depth.
0:09:40 > 0:09:43- This is called stereoscopic vision.
0:09:44 > 0:09:46- Stereoscopic vision...
0:09:46 > 0:09:50- ..allows us to create a 3D picture - of our surroundings.
0:09:50 > 0:09:54- Here, at Bangor University, - a team led by Dr Simon Watt...
0:09:55 > 0:09:59- ..tests this ability, - which varies from person to person.
0:10:01 > 0:10:03- This machine is unique.
0:10:04 > 0:10:07- It can push our stereoscopic vision - to its limit.
0:10:08 > 0:10:13- Two screens show a different image - for each eye.
0:10:13 > 0:10:18- Your eyes are separated, so they see - the world from different positions.
0:10:18 > 0:10:20- They get slightly different images.
0:10:20 > 0:10:25- There's information in that about - the depth structure of the world.
0:10:25 > 0:10:29- If you can replicate that by - presenting one image to one eye...
0:10:30 > 0:10:34- ..and a different image to the other - you can simulate that situation.
0:10:35 > 0:10:39- A series of mirrors allows the team - to produce an image...
0:10:40 > 0:10:43- ..which is as near or far - from the eye as they choose.
0:10:44 > 0:10:48- During the test, different images - reach the left and right eye.
0:10:48 > 0:10:52- The brain must combine them - to create a 3D pattern...
0:10:52 > 0:10:55- ..just as it does in everyday life.
0:10:55 > 0:10:59- As the test continued, - I found it increasingly difficult...
0:11:00 > 0:11:02- ..and my eyes were strained.
0:11:03 > 0:11:08- 3D technology works by forcing us - to use our stereoscopic vision...
0:11:08 > 0:11:13- ..to focus on images in front - of the screen rather than on it.
0:11:14 > 0:11:19- Everyone's sight is different, so - this isn't enjoyable for everyone.
0:11:20 > 0:11:25- With a better understanding - how stereoscopic vision works...
0:11:26 > 0:11:30- ..the aim is to improve the - experience of watching a 3D movie.
0:11:31 > 0:11:35- A percentage of the population - is stereoblind...
0:11:35 > 0:11:39- ..and can't form 3D images - using stereoscopic vision.
0:11:39 > 0:11:44- This doesn't necessarily render them - incapable of perceiving depth.
0:11:45 > 0:11:49- If you don't have stereo vision, - you're losing one signal of many.
0:11:49 > 0:11:53- If you're trying to judge - how far apart two things are...
0:11:54 > 0:11:55- ..you'd really struggle.
0:11:56 > 0:11:58- And maybe catching a moving ball.
0:11:58 > 0:12:02- For everyday perception - of the world, you're less certain...
0:12:02 > 0:12:04- ..but not in a way you'd notice.
0:12:05 > 0:12:07- The brain uses size - to perceive depth.
0:12:08 > 0:12:10- So it is possible to trick it.
0:12:10 > 0:12:14- In this example, it thinks the chair - and me are the normal sizes.
0:12:16 > 0:12:18- I look small in this position.
0:12:22 > 0:12:24- And now, I'm the correct size.
0:12:25 > 0:12:26- Hello, Katie!
0:12:28 > 0:12:29- .
0:12:32 > 0:12:32- Subtitles
0:12:32 > 0:12:34- Subtitles- - Subtitles
0:12:37 > 0:12:41- We blink around 15 times per minute - without really noticing.
0:12:41 > 0:12:43- Blinking cleans the eye...
0:12:43 > 0:12:48- ..but it also means we spend - 10% of our waking hours in darkness.
0:12:48 > 0:12:51- Blinking helps us concentrate.
0:12:51 > 0:12:56- During a conversation, we tend to - blink the same time as the speaker.
0:12:56 > 0:12:59- Around 10% of us - are likely to sneeze...
0:12:59 > 0:13:03- ..when we move from darkness - into a bright light.
0:13:03 > 0:13:06- This is known as - the photic sneeze reflex.
0:13:06 > 0:13:09- Around 8% of men are colour-blind...
0:13:09 > 0:13:13- ..and can't distinguish colours - containing red or green.
0:13:13 > 0:13:17- Women can be colour-blind, - but it's far more unusual.
0:13:19 > 0:13:22- Eating carrots won't improve - your night vision.
0:13:22 > 0:13:26- This was a story invented - during World War II...
0:13:26 > 0:13:30- ..to conceal the fact that Britain - was using a new type of radar.
0:13:31 > 0:13:35- But carrots do contain vitamin A, - which is good for the eyes.
0:13:38 > 0:13:41- At the University Of Bath, - Dr Michael Proulx...
0:13:41 > 0:13:46- ..is developing a device with which - you can 'see' with your ears.
0:13:47 > 0:13:51- Low notes are down here. - High notes are things further away.
0:13:52 > 0:13:53- I must close my eyes.
0:13:54 > 0:13:59- The camera on the glasses turns - what's in front of me into sound...
0:13:59 > 0:14:02- ..which travels from my left ear - to my right ear.
0:14:03 > 0:14:07- The further away the object is, - the higher the pitch of the note is.
0:14:08 > 0:14:11- If the pen is lying flat, - the sound is constant.
0:14:14 > 0:14:16- I hear one constant note.
0:14:17 > 0:14:19- I'll change the orientation of it.
0:14:19 > 0:14:24- The pen is at an angle, with the - left end closer than the right...
0:14:24 > 0:14:28- ..so the pitch of the note - rises from left to right.
0:14:31 > 0:14:36- It's possible to use the glasses - to identify more complex shapes...
0:14:40 > 0:14:41- ..such as letters...
0:14:42 > 0:14:45- That's a letter O.
0:14:45 > 0:14:47- ..and even words.
0:14:48 > 0:14:49- Oh, my gosh!
0:14:55 > 0:14:57- It sounds like W O W.
0:14:57 > 0:15:01- I hear the same sound in the right - as the one in the left...
0:15:03 > 0:15:05- ..with and O in the middle.
0:15:06 > 0:15:10- It was difficult. - I had to concentrate really hard.
0:15:10 > 0:15:13- But I did read a word. - I'm happy with myself.
0:15:14 > 0:15:17- The next step - is to learn to locate objects.
0:15:21 > 0:15:24- It's constant, - so it must be in the middle.
0:15:25 > 0:15:27- I'm getting the hang of this device.
0:15:28 > 0:15:32- There's slightly more noise - on the left, so it must be here.
0:15:33 > 0:15:34- There it is.
0:15:35 > 0:15:39- The glasses can pick up - other objects on this table...
0:15:39 > 0:15:42- ..which then adds a different sound.
0:15:43 > 0:15:47- I had to try to focus - on the object in question...
0:15:47 > 0:15:50- ..and ignore the other objects.
0:15:53 > 0:15:56- I'll hear this sound - in my sleep tonight!
0:15:57 > 0:16:02- Next, the biggest challenge yet - - using the glasses to follow a path.
0:16:02 > 0:16:03- Did you notice the sound change?
0:16:03 > 0:16:05- Did you notice the sound change?- - Yes.
0:16:06 > 0:16:11- When I walked down the path, sound - came in waves, then it was constant.
0:16:11 > 0:16:16- When I hit the bricks, the sound - was different but constant again.
0:16:19 > 0:16:24- I went left but I walked into grass - because I hadn't turned enough.
0:16:25 > 0:16:28- Sound came in waves - but it was constant.
0:16:28 > 0:16:33- I turned again and I got a smooth, - constant sound and then waves.
0:16:33 > 0:16:35- That's how I knew I was on the path.
0:16:35 > 0:16:40- The initial application is to find - ways that the visually impaired...
0:16:41 > 0:16:44- ..can use it to do things - sighted people take for granted.
0:16:45 > 0:16:47- Being able to navigate your way - through a city.
0:16:48 > 0:16:51- Also if you're in - an unfamiliar location...
0:16:51 > 0:16:55- ..and you need to find - something simple, like an exit.
0:16:57 > 0:17:01- Michael gives me one more challenge - - avoiding obstacles.
0:17:05 > 0:17:09- The sound was constant and I knew - how the grass and the path sounded.
0:17:10 > 0:17:13- Once the sound changed, - I knew he was there.
0:17:13 > 0:17:16- I just had to work out - which way I should move...
0:17:17 > 0:17:20- ..by listening - on which side the sound was.
0:17:20 > 0:17:23- Then I knew which side to choose.
0:17:28 > 0:17:29- Oh!
0:17:30 > 0:17:32- LAUGHTER
0:17:40 > 0:17:44- These spectacles - turn everything upside-down.
0:17:45 > 0:17:49- They turn a simple task - into a difficult challenge.
0:17:51 > 0:17:53- Such as catching a ball!
0:18:00 > 0:18:02- Ready? I'll count to three.
0:18:03 > 0:18:05- One, two, three!
0:18:05 > 0:18:06- One, two, three!- - Ooh!
0:18:09 > 0:18:10- One, two, three.
0:18:11 > 0:18:15- Everything's upside-down, - so when the ball goes up...
0:18:15 > 0:18:19- ..the body instinctively bends down - to catch it.
0:18:26 > 0:18:31- Your head tells you to go one way - but you should go the other way.
0:18:32 > 0:18:36- After a while, the brain adjusts - to the spectacles...
0:18:36 > 0:18:39- ..and catching becomes easier...
0:18:40 > 0:18:41- ..for some people!
0:18:42 > 0:18:43- Did you throw it?
0:18:56 > 0:19:00- What happens - once the signals reach the brain?
0:19:00 > 0:19:05- The brain must process them and - create a picture of our environment.
0:19:10 > 0:19:12- Here at CUBRIC, - Cardiff University...
0:19:13 > 0:19:16- ..Dr John Evans shows me - how the brain does this.
0:19:19 > 0:19:22- What part of the brain - deals with what we see?
0:19:22 > 0:19:25- This is a model of the brain. - This is the front.
0:19:26 > 0:19:30- The part of the brain - which is responsible for sight...
0:19:30 > 0:19:33- ..is the visual cortex, at the back.
0:19:33 > 0:19:37- It deals with any image which - reaches the brain via the eyes.
0:19:40 > 0:19:44- John's series of MRI tests will show - how my visual cortex works.
0:19:47 > 0:19:50- Are you ready for the first task?
0:19:50 > 0:19:51- Yes.
0:19:52 > 0:19:55- Look at the cross - in the centre of the screen.
0:20:07 > 0:20:11- These tests will show that different - areas of the visual cortex...
0:20:12 > 0:20:16- ..perform different tasks - while the brain processes images.
0:20:19 > 0:20:24- The left side of the brain - processes things on the right.
0:20:25 > 0:20:29- The right side of the brain - processes things on the left.
0:20:31 > 0:20:37- The activity is greater in the green - areas when focusing on the left.
0:20:37 > 0:20:42- The activity in the red areas is - greater when focusing on the right.
0:20:42 > 0:20:47- The activity in the visual cortex - depends on where the activity is.
0:20:48 > 0:20:50- Things can become more complicated.
0:20:51 > 0:20:54- There's an area called V5 - at the back of the brain...
0:20:54 > 0:20:59- ..and it's primarily - associated with motion.
0:21:01 > 0:21:05- If we compare the activity - when you look at a still image...
0:21:05 > 0:21:09- ..to the activity - when you watch moving images...
0:21:09 > 0:21:12- ..we can see an increase - in these areas.
0:21:12 > 0:21:16- It's vital - for processing moving images.
0:21:17 > 0:21:21- How does the brain recognize faces - and read expressions?
0:21:21 > 0:21:25- John puts me back in the MRI scanner - to undergo another test.
0:21:26 > 0:21:31- Anwen, for the next task you'll see - images of places or faces.
0:21:32 > 0:21:36- People are very good - at remembering faces.
0:21:36 > 0:21:39- We pick out faces in great detail.
0:21:39 > 0:21:44- One part of the brain is important - when we process this information.
0:21:45 > 0:21:48- It's known as - the fusiform face area.
0:21:48 > 0:21:52- It's at the base of the brain, - in this area.
0:21:52 > 0:21:57- It works harder when you look at - faces than when you look at places.
0:21:58 > 0:22:00- What happens to this information?
0:22:01 > 0:22:04- When the brain - has processed the information...
0:22:05 > 0:22:07- ..it decides where it should go.
0:22:07 > 0:22:11- Should it make a decision - as a result of what the eyes saw?
0:22:11 > 0:22:15- The information is passed - to upper areas of the brain...
0:22:16 > 0:22:19- ..but that's another story!
0:22:22 > 0:22:27- Different parts of the brain process - different elements of what we see.
0:22:28 > 0:22:31- From shapes and colours - to movement and faces.
0:22:33 > 0:22:38- The brain gives us a complete - picture of the world around us.
0:22:39 > 0:22:43- That's why we rely more heavily - on vision than our other senses.
0:22:44 > 0:22:47- Next week, we'll focus on hearing.
0:22:48 > 0:22:51- How important is hearing - in everyday life?
0:23:08 > 0:23:10- S4C subtitles by Eirlys A Jones
0:23:10 > 0:23:11- .