Stripping Down Science (20 page)

This shows that, whatever the extra connections are in the brains of people with this form of synaesthesia, they must lie downstream of the system that selects a word to use but upstream of the system that translates this thought into a physical word we can say. How that's for research you can get your teeth into?

Most people are comfortable with the idea that what goes on in your own head is for your mind's eyes only. That's because, put simply, thoughts are nothing more than clusters of nerve cells firing off in a certain sequence. And, unless you choose to tell someone what you're thinking, this means it's impossible for anyone else to know. At least, that
was
the case. Because recent advances in brain scanning and mapping techniques mean that scientists are moving ever closer to being able to decode what's going through the heads of the average person, ushering in an era when your thoughts will no longer be your own.

This was elegantly demonstrated by a team of US scientists led by University of California Berkeley researcher Jack Gallant.
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He and his colleagues have developed computer software that, based on the pattern of brain activity in a human subject, can predict with 90% accuracy what image – from a selection of thousands – a person is looking at.
The technique uses functional magnetic resonance imaging (fMRI), an existing technology that can decode nerve activity by comparing how much energy is being consumed by each region of the brain at any one time. When a part of the brain becomes busily engaged processing a piece of information, its oxygen demand shoots up, which boosts the local blood flow, and this is what the scanner can see.

What the Berkeley team have done is develop a system that looks very closely at the regions of the brain concerned with visual processing. By showing human subjects a series of 1750 different photographs and then comparing how the brain responded to each image, the team were able to match up, at very high resolution, how different aspects of the photographs produced correspondingly different brain activities. After five hours, the system had learned how the brains of the human volunteers were responding to individual details of the visual images.

Next, to find out how well it really knew its subjects, the researchers put the software to the test. They asked it to predict the pattern of brain activity that would be produced when the subjects viewed 120 different images that they had never
seen before. The predictions were then compared with the scan results collected when the subjects viewed the images for real. Astonishingly, the software was getting it right 92% of the time in one volunteer and 72% of the time in the other. This is compared with a success rate of 0.8% (1:120) which would be achieved if random guesswork were being used.

To find out whether the system could cope with much larger numbers of images, the team then tested its performance against a suite of 1000 photographs, achieving a similar success rate of 82%. They also re-tested the same participants two months and then 12 months later and found that the system was still working as well as it had previously, indicating that once it had learned how a subject's brain processes visual information, the system could continue to work reliably into the future.

Thinking ahead, Jack Gallant points out that these results show ‘that it may soon be possible to reconstruct a picture of a person's visual experience from measurements of brain activity alone.' In other words, go one step further and, by reading off the pattern of brain activity, translate what is in someone's mind's eye into a physical
picture on a computer screen. ‘Imagine a general brain-reading device that could reconstruct a picture of a person's visual experience at any moment in time.'

Which means that ‘turning your dreams into reality' could take on an entirely new meaning in future.

‘Brain' box

The human brain contains about 100 billion nerve cells, each making an average of 1000 connections to other brain cells. These cellular links are known as synapses and when a brain cell becomes active, the synapses squirt out nerve transmitter chemicals (neurotransmitters) that lock onto adjacent nerve cells and alter their activity. By making, breaking or altering the relative strengths of these connections – a process called long-term potentiation (LTP) – the brain creates mouldable neural networks that can store and process information, including making memories.

This means that when it encounters certain stimuli, the brain responds with characteristic patterns of activity, which is what Jack Gallant and his team were seeing in their fMRI study.

When someone's said to be brain dead, doctors usually mean a patient who is in what's called a persistent vegetative state. This is where an individual can appear to be awake, their eyes can be open, they even periodically seem to go to sleep, but they remain completely unaware, unreactive and unresponsive to the world around them. Most remain in this state permanently.

People who fit this category are usually victims of severe head injuries sustained in road traffic accidents or falls, or patients who have suffered a lack of oxygen supply to the brain through drowning, carbon monoxide poisoning, heart attacks, or strokes. Under these circumstances, there is usually significant damage to the brain. The person remains physically ‘alive' because the primitive parts of the nervous system, which control heart rate, blood pressure and breathing, are still working. But the destruction of the ‘higher' brain regions that make a healthy individual conscious renders the person permanently vegetative: awake, but unaware.

Or so we thought. Because a Cambridge-based brain researcher, Adrian Owen,
⁶⁹
recently succeeded in communicating, using a brain scanner, with a patient written off as brain dead more than five years previously. The team had wondered whether some vegetative patients are unresponsive because the regions of the brain required to initiate bodily reactions have been too badly damaged. They reasoned that if someone was in this position they might nonetheless be able to see things in their mind's eye or imagine themselves performing certain tasks if instructed to do so.

So over a three-year period, the researchers screened 23 patients diagnosed previously as being in vegetative states. With the participants in a brain scanner, they asked them to perform two imaginary tasks. The first was to see themselves playing tennis. This triggers high levels of activity in a region of the brain called the supplementary motor area (SMA), which is concerned with planning movements. The second task was to imagine walking around home or a familiar place. This activates a different brain region – the
parahippocampal gyrus – which is concerned with navigation and sense of direction.

The researchers had already demonstrated, using healthy volunteers, that a functional MRI (fMRI) scanner could detect the differences in brain activity between these two tasks. This meant that if any of the vegetative patients could understand the instructions, such as ‘start imagining playing tennis now', then they ought to be able to alter their thoughts accordingly, which the scanner would be able to pick up.

When the results from the patients began to roll in, the researchers were shocked. Four of the 23 showed signs of awareness and, incredibly, by thinking about tennis to indicate a positive and walking around his house to indicate a negative, one of the patients was even able to answer ‘yes' and ‘no' questions such as, ‘Is your father's name Thomas?'

According to Adrian Owen, ‘We were astonished when we saw the results of the patient's scan and that he was able to correctly answer the questions that were asked by simply changing his thoughts. Not only did these scans tell us that the patient was not in a vegetative state but, more importantly, for the first time
in five years it provided the patient with a way of communicating his thoughts to the outside world.'

What this study shows is that not all patients who appear to be brain dead actually are. But thanks to an imagined game of tennis or a trot around home it might be possible to reach those that are aware and reopen a window into the world for them.

Ask a friend to look at a photo of a face and you'd expect them to be able to tell you what sort of mood the pictured person was in, wouldn't you? Charles Darwin felt the same way and said so in his 1872 book
The Expression of the Emotions in Man and Animals
. Facial expressions, he thought, are a universal window into emotion, unaffected by creed or culture.

Scientists have since taken this belief much further, leading to the creation in the 1970s of a concept called FACS (facial action coding system). Using this approach, a set of universal facial images were created to represent the seven basic human displays of emotion: ‘happy', ‘sad', ‘angry', ‘fearful', ‘neutral', ‘surprised' and ‘disgusted'. These, they argued, should be recognisable by everyone. But some scientists frowned on this convenient claim of a cross-cultural appreciation for facial expression, so University of Glasgow psychologist Rachael
Jack decided to put it to the test.
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And, unfortunately for Darwin, it turns out that some of these so-called ‘universal' facial expressions are commonly confused by different cultures. Or even lost in translation, you might say.

The scientists flushed out this myth by recruiting a group of western Caucasian volunteers and a similar-sized group of East Asians, most of them Chinese students recently arrived in Britain to study. The subjects were asked to look through a collection of 56 images displaying the seven key FACS-coded facial emotions. The picture mix included both oriental and western faces.

As they regarded each image, the participants were asked to decide what emotion was being displayed. While they were doing this, the researchers also monitored the subjects' eye movements to discover the order, timing and priority with which they scrutinised the different regions of the faces presented. The western Caucasian participants performed with consistent accuracy across the entire panel of faces and emotions, but the East Asian subjects fared much less well, confusing ‘disgusted' with ‘angry' faces,
and substituting ‘surprised' for ‘fearful' faces.