area V4 V4 is one of the main subdivisions of the visual cortex, in the occipital lobes of the cerebral cortex. V4 was named by Semir Zeki in the 1970s and has been closely associated with the perception of colour, although it is not limited to this role.
attention A key cognitive and perceptual process in which the brain prioritizes the processing of some signals at the relative expense of others. There are many types of attention (such as attention to spatial locations, objects or object features). Attention is usually studied in the context of vision, but it is present for other senses as well.
cerebral cortex The deeply folded outer layers of the brain, which take up about two-thirds of its entire volume and are divided into left and right hemispheres that house the majority of the ‘grey matter’ (so called because of the lack of myelination that makes other parts of the brain seem white). The cerebral cortex is separated into lobes, each having different functions, including perception, thought, language, action and other ‘higher’ cognitive processes, such as decision making.
change blindness A phenomenon in which surprisingly large changes in a visual scene can go unnoticed if there is a gap between the images or if there are other more salient changes accompanying the transition. Change blindness, like inattentional blindness, suggests that our perception of the world may not be as reliable as we usually assume.
colour constancy The process by which our visual system compensates for changes in illumination that affect the balance of light waves reflected from coloured surfaces. For example, a bed of roses will result in a different mixture of wavelengths at dawn than at midday yet, even though colour depends precisely on this mixture, we will perceive the roses as a particular shade of red in both cases.
frontal lobes One of the four main divisions of the cerebral cortex and the most highly developed in humans compared to other animals. The frontal lobes (one for each hemisphere) house areas associated with decision making, planning, memory, voluntary action and personality.
inattentional blindness Related to change blindness, in inattentional blindness visible but unexpected objects can go unnoticed if attention is fully occupied elsewhere. In a famous demonstration by Dan Simons, volunteers failed to notice a man dressed as a gorilla walking across a basketball court when they were focusing on counting the number of successful passes.
motor cortex Part of the cerebral cortex, located towards the rear of the frontal lobes, which is responsible for the planning and execution of actions. The primary motor cortex sends control signals directly to the spinal cord and from there to the muscles. Higher-order motor areas are involved in more abstract sequencing and planning of actions and in initiating voluntary actions.
superior colliculus A pair of small structures beneath the cerebral cortex that play an important role in guiding fast visual reflexes, such as object tracking. Visual signals travelling via the superior colliculus do not reach the cortex.
Our eyes are the mere starting point for seeing colours. The eyes contain special receptors for detecting the wavelength of light, this being the physical property of light most closely associated with colour. However, if we move an apple from sunlight to indoor candlelight, then we still see it as red even though the wavelengths of light reflecting off it can be very different due to the different lighting conditions. This aspect of colour is computed by the brain instead of the eyes. Moreover, some of the colours we can see (such as magenta) don’t have a corresponding wavelength – they are entirely constructed by the brain. There is a part of the brain – ’area V4’ – present in both hemispheres, that is responsible for the perception of colour. Damage to this region of the brain creates the experience of seeing the world in black and white. Why would there be a dedicated region of the brain for processing colour? The V4 region of the brain is thought to compute ‘colour constancy’ – that is, it infers the colour of a surface taking into account the lighting conditions. This ability may have evolved in our primate ancestors due to the need to reliably identify food sources, such as red fruit in green foliage.
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The brain tries to figure out the true colour of a surface independent of the lighting conditions; so seeing colour isn’t just detecting wavelengths of light.
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There aren’t seven colours in a rainbow. We just think there are because we have only a limited number of words for describing the colours we see. The way that we divide colours into categories affects the way we see them. For instance, some cultures don’t have separate words for green and blue, and these people are worse at telling colours apart that are greeny blue (such as turquoise).
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3-SECOND BIOGRAPHIES
EDWIN LAND
1909–91
Proposed one of the first accounts of colour constancy
SEMIR ZEKI
1940–
Famous for his studies on area V4
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Jamie Ward
Although the physical wavelength of light reflected from the green squares is the same, one of them is perceived by the brain as much brighter.
Patient GY had a car accident as a teenager that damaged a small region of his brain and meant that he was ‘blind’ in one part of his visual field. When shown a moving light in his ‘blind’ field, he would claim not to be able to see it. When forced to guess whether the light moved to the left or right he would be more than 90 per cent accurate despite maintaining that he could not see it. This paradox is termed ‘blindsight’. The key to understanding it comes from the fact that there is not just one route that connects the eyes to the brain but many (around ten routes in humans), so damaging the brain might affect one route selectively (whereas damaging the eyes would tend to affect them all). These routes have evolved for different functions – one uses light to calibrate the biological clock (useful for getting over jet lag) and another is used to orient the eyes to sudden changes. These routes are still functioning in patients such as GY, enabling him to ‘see’ to some extent. The route that is damaged in GY (and others like him) is the main route involving the cortex – it is important for seeing fine detail and is closely linked to the conscious experience of seeing.
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Some patients with damage to the visual parts of the brain claim not to be able to see something but can then accurately guess what they are seeing. This is called blindsight.
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We all occasionally move our eyes to something that turns out to be important without knowing why we moved them there. It is almost as if our eyes can see something that ‘we’ cannot yet see. However, this isn’t a discrepancy between the eyes and the brain. Rather it reflects two different routes within the brain itself – a fast seeing route (via the superior colliculus) that moves the eyes and a slow seeing route (via the cortex) than can detect the details of what is seen.
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NEURAL CORRELATES OF CONSCIOUSNESS
3-SECOND BIOGRAPHIES
GEORGE RIDDOCH
1888–1947
Neurologist who studied visual impairments in brain-injured soldiers in the First World War
LARRY WEISKRANTZ
1926–
Researcher who coined the term ‘blindsight’
NICHOLAS HUMPHREY
1943–
Researcher and philosopher with an interest in vision
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Jamie Ward
Blindsight means you don’t always get the whole picture. You may not have seen it, but your brain saw it.
For a small percentage of the population, words may be coloured (so Tuesday might be blue), music may have a taste, or numbers may be visualized on a twisting, turning landscape. This remarkable way of experiencing the world is termed synaesthesia. People with synaesthesia have additional sensations (such as someone smelling as well as hearing a sound) that appear effortlessly to them. It emerges early in life and tends to be stable; so if Tuesday is blue now, then it will be tomorrow and next year. One key to understanding this is to realize that our conscious perceptions (such as of colour) are created by the brain, so they can be turned on not only by our sensory organs but also by activity in other parts of the brain. In synaesthetes, the colour centre of the brain may be turned on not only by seeing colours but also by hearing words. The latter may happen because people with synaesthesia have unusual patterns of connectivity between regions of the brain that tend to be more segregated in others. This rewiring may be genetic (synaesthesia runs in families) but it is not a disorder. For instance, having synaesthesia may improve memory.
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Our perceptions aren’t always triggered via our sensory organs (eyes, ears, etc) but can be triggered by activity in other regions of the brain. For synaesthetes, seeing colours could result from hearing someone speaking.
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Daniel Tammett used his synaesthesia to help him remember the digits of pi to over 20,000 decimal places. For Daniel, each digit has its own colour, size and shape and the sequence of digits is a colourful landscape along which he can walk in his mind’s eye. For people without synaesthesia, visualizing things often improves their memorability, and linking sequences to familiar routes can be used as a strategy for learning, say, the order of a pack of playing cards.
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NEURAL CORRELATES OF CONSCIOUSNESS
3-SECOND BIOGRAPHIES
FRANCIS GALTON
1822–1911
Victorian polymath who popularized the notion of synaesthesia
V. S. RAMACHANDRAN
1951–
Neuroscientist who links synaesthesia with evolution of language and creativity
RICHARD CYTOWIC
1952–
Researcher and author of The Man Who Tasted Shapes
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Jamie Ward
Sensory substitution devices convert information from one sense into another. Their normal purpose is to enable blind people to ‘see’ by using their intact senses of hearing or touch. For instance, one early device used an array of pins on the wearer’s back to create a two-dimensional tactile impression of a visual scene. This enabled blind people to recognize distant objects and even created a feeling of the objects being ‘out there’ in front of them, even though it was only their back that was stimulated. Modern versions are miniaturized and stimulate the user’s tongue, being linked, via a computer, to a webcam on their head. Alternative devices use sounds to convey vision – for instance, different pixels in an image are translated to different pitches and different points in time. After training, users (blind or sighted) come to recognize the sound waves as ‘shapes’, and the sounds activate parts of the brain normally dedicated to visual or tactile shape detection. The ability of the brain to adapt to these devices is a striking example of plasticity that, in some very real sense, creates a cyborg – a functioning entity that is part man, part machine.
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Technology can be developed that translates vision into hearing or touch, providing blind people some access to the visual world. The brain translates the auditory or tactile input back into something like vision.
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Is the success of sensory substitution dependent on the user having previous vision? Could a person, blind from birth, report new experiences as a result of these devices? There is no straightforward answer. Someone blind from birth would not fully understand what vision is like. People who became blind early in life have reported unusual experiences after using these devices (sensing something in front of them as their back is stimulated) but it is unclear if this is ‘seeing’ (they don’t report shades of light and dark).
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3-SECOND BIOGRAPHIES
PAUL BACH-Y-RITA
1934–2006
Pioneered this field from the 1960s with his tactile-visual devices
KEVIN O’REGAN
1948–
Scientist and philosopher who argues that vision can be experienced from other senses
PETER MEIJER
1961–
Inventor of an auditory sensory substitution device the ‘vOICe’
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Jamie Ward
The visual world feels uniformly rich and detailed rather than patchy. However, our everyday experience of searching for a ‘hidden’ object – say, our car keys – that turns out to be right in front of us suggests that we don’t process all the objects in our field of view to the same degree. There have been some fun experiments that illustrate this. If you are counting the number of passes in a basketball game, you may fail to notice a man in a gorilla suit who walks across the court (this is called inattentional blindness). Similarly, if a library assistant ducks below the counter to find your book and a new assistant pops up in the same place, then you may not notice the difference at all (this is termed change blindness). Vision and the rest of our senses are continually bombarded with information and the brain has developed a mechanism – attention – that acts as a filter by allowing some information to be prioritized (such as by amplifying its neural signal) at the expense of other information. This prevents us from being continually distracted (so we don’t notice the touch of our clothing because we don’t attend to that signal), but ‘missing the obvious’ can sometimes be the price that is paid.
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Not all objects in a crowded visual scene get processed fully. The brain contains a filtering mechanism (attention) that prioritizes a few things at a time.
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There are similar examples in the domain of hearing. If we listen to several streams of conversation at the same time, we can, to some extent, filter out the irrelevant ones. We may even fail to notice when an unattended voice changes from male to female or English to German. In this example, unattended information, processed in the auditory parts of the brain, is not propagated to ‘higher’ regions of the brain (like the prefrontal and parietal areas) that allow it to be fully processed.
RELATED BRAINPOWER
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HOW WE PICK UP A CUP OF COFFEE
3-SECOND BIOGRAPHIES
DONALD BROADBENT
1926–93
Psychologist who conceptualized attention as a filter
RONALD RENSINK
1955–
Conducted pioneering studies on change blindness
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Jamie Ward
Pay attention. How many passes did you count? How many slam dunks? And why is Michael Jordan wearing that gorilla suit?
The skill of hand-eye co-ordination is not as simple as it seems, as decades of research on robotics has found. Locating the cup of coffee is the first challenge. Our visual system can tell us where it is located on the retinal image, but we do not want to reach inside our eyes to find the coffee cup. To locate the coffee cup in the external world, we need to know the position of the eyes in the socket and the position of the head relative to the body (depth is yet another issue). So signals from the eye and neck muscles need to be linked to vision. In this way, we transform a visual image from something that is centred on the eyes to something that is centred on the body and, hence, can be acted upon. There appear to be separate pathways in the brain for locating and acting on an object (such as picking it up) versus knowing what the object is (such as recognizing it as a cup of coffee), although the two pathways normally work together effortlessly. Knowing what an object is affects how we interact with it – think picking up a paperweight versus an egg. Robots trained to pick up a paperweight will get sticky fingers when encountering the egg unless they have some kind of object recognition system.
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Locating a cup of coffee involves linking visual information with information about the current posture of the body, which involves highly specialized mechanisms in the brain.
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Computer vision and robotics can learn important lessons from the human brain. One lesson to be learned is that the body is important. We actively explore the world by moving our eyes, head and body, and this exploration gives us new sources of information. For instance, noticing how the visual world changes as a result of moving our head provides clues to depth and occlusion.
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3-SECOND BIOGRAPHIES
MEL GOODALE & DAVID MILNER
1943– and 1943–
Championed the idea that vision-for-action is different from vision-for-perception
RICHARD ANDERSEN
1950–
Neuroscientist who has explored how visual space is transformed from eye to body co-ordinates
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Jamie Ward
Brain the size of Jupiter, speaks 400 languages, can calculate pi to infinity, but still can’t pick up a cup of coffee without spilling it.
Oliver Sacks, now into his ninth decade and still writing prolifically, is Professor of Neurology at the New York University School of Medicine. British born and a graduate of Oxford and New York universities, he has lived and worked in the United States since the 1960s.
Sacks has always striven to unite science with the arts, to find a sympathetic, universally comprehensible way to explain the behaviour of the brain and consciousness without neglecting the physiology and neural circuitry that underpins it. His bestselling books are based on case studies of his patients’ and his own experiences (as a migraine sufferer and an experimenter with mind-altering drugs, for example). He presents the diseased, damaged, or broken mind not through the clinical observations of an Olympian physician, but from the horse’s mouth, in the words of the patients themselves, whether they are living with Tourette’s, Parkinson’s, aphasia, autism or other conditions. This offers the opportunity to report on the glories that can come from an ‘abnormal’ response to the world, as well as the problems it presents, an approach that accommodates both the pragmatic and the poetic. To the New York Times, Sacks is the Poet Laureate of Medicine, and in 2001 he was awarded the Lewis Thomas Prize for Writing about Science. His most famous book is probably The Man Who Mistook His Wife for a Hat, 24 essays reporting in from the extremes of the mind.
As a neurologist, Sacks is also known for the work he did in the 1960s with survivors from the 1920s pandemic of sleepy sickness (encephalitis lethargica), who had been comatose for almost 40 years. Sacks believed that the new experimental drug L-DOPA, although designed to improve dopamine uptake as a therapeutic intervention in Parkinson’s disease, might wake them up; and it did, but the outcome was not universally happy. His second book Awakenings, is an unflinching account of what happened.
Sacks has been showered with awards and his work is invaluable in bringing difficult conditions to the attention of the everyday reader. However, he remains a somewhat controversial figure. A few fellow peers feel that he could be exploiting his patients as material for his literary career; others, that he is possibly too idiosyncratic and insufficiently rigorous in his reporting methods. Yet in terms of public profile, he could be described as neurology’s Stephen Hawking: his humane, empathetic, and engaging approach makes him the neurologist most likely to be recognized by non-neurologists.
Born in London
1954
BA in physiology and biology from The Queen’s College, Oxford
1966
Worked at Beth Abraham Hospital, New York, with survivors from the 1920s encephalitis lethargica pandemic
1966–2007
Instructor and later Clinical Professor of Neurology at Albert Einstein College of Medicine, New York
1973
Published Awakenings, a report on the experiences of his sleep sickness patients
1985
Published The Man Who Mistook His Wife for a Hat and Other Clinical Tales, his first bestseller
1992–2007
New York University School of Medicine
1995
Published An Anthropologist on Mars: Seven Paradoxical Tales about people with brain disorders who also manage creative high-profile lives
2007
Joined the medical faculty of Columbia University Medical Center as professor of neurology and psychology
2007
Published Musicophilia: Tales of Music and the Brain
2010
Published The Mind’s Eye, case studies about the experience of visual impairment
2012
Published Hallucinations, studies of his own and his patients’ experience of hallucinations, both disease- and drug-induced.
2012
Appointed Professor of Neurology at the NYU School of Medicine and consulting neurologist at its Epilepsy Center
Alien hand syndrome is found after certain types of brain damage. Patients feel that movements of a limb (normally the arm) are not initiated by them and, hence, feel ‘alien’, as if the limb has ‘a mind of its own’. The movements can be meaningful or meaningless. For instance, the alien hand might unzip a sweater that the other hand just zipped up, or the alien hand may levitate spontaneously, making ‘tentacular’ movements of the fingers. The character of Dr. Strangelove, in the movie of the same name, displayed this symptom. There are multiple regions of the brain involved in producing actions. The primary motor cortex sends signals down the spinal cord to produce movements of the limbs. However, the primary motor cortex itself receives signals from other parts of the brain in the frontal lobes that shape and control our actions. Normally, these parts of the brain function together – our actions don’t feel alien because the parts of the brain that produce movements communicate with the parts of the brain that control and guide action. If our motor cortex becomes disconnected from these controlling regions, then movements are produced that are unexpected and, hence, ‘alien’.
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Your arm might feel out of control if your motor cortex becomes disconnected from other parts of your brain.
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The alien hand syndrome might have something in common with hallucinations. The former involves movement and the latter involves sensations (hearing voices or seeing faces that aren’t there), so they are superficially different. However, they may reflect similar kinds of brain mechanisms, that is they reflect spontaneous activity within sensory or motor regions of the brain that are ‘unexpected’ by higher regions of the brain.
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3-SECOND BIOGRAPHIES
KURT GOLDSTEIN
1878–1965
Reported the first known case in 1908
STANLEY KUBRICK
1928–99
Directed the movie Dr. Strangelove – how did he know about the symptom?
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