Tonight I have been pleasantly surprised to have been awarded a Highly Commended prize at the Max Perutz Science Writing Award, sponsored by the MRC. I got to spend a lovely night in the Gherkin, where we drank good wine, ate delicious food and, thanks to the DJ, danced a bit of Tango! Thanks also to the MRC for organising a Master Class on writing with poet Lavinia Greenlaw and the Guardian's science journalist Alok Jha.
The essay below is considerably more down to earth and less philosophical than my previous entry, though I hope it still is able to convey my amazement at the phenomena we call vision and consciousness.
The essay below is considerably more down to earth and less philosophical than my previous entry, though I hope it still is able to convey my amazement at the phenomena we call vision and consciousness.
Memories of a brain cartographer
Look. The world before you seems simple. It almost appears as though, somewhere inside your head, a cinema projector displays what your eyes capture and interpret. But that's not how we function. Instead, your brain is a cartographer, housing on its cortex a multitude of sensory, mostly visual, maps. Like regular maps, brain maps are drawn in a continuous and fluid way. Just as neighbouring countries are placed adjacent on a map, neurones that respond to similar visual locations are also grouped together.
Depending on the task at hand, our brains pick the best map to get the job done. When we talk about the Earth, depending on the context we interpret it in terms of political, geographical or weather maps, each with its rules and highlights. Just like a map maker, the brain interprets the world surrounding us by simplifying it: it splits it into categories, uses landmarks, and traces frontiers.
Over a dozen maps have recently been found in humans, spread about the brain's cortex. Some maps detect the edges and corners that delineate the outlines of objects. Others only take heed of movement or colour. Another few just seem to predict where you'll soon lay your eyes. Still others are centred on where your eyes are pointed, or relate to the position of your head or hands.
So, that variety is fascinating, but what does this add to science? Well, much of current brain science focusses on labelling a particular brain region with some function. Research programmes often try to find the "centre" for, say, envy, face perception or motivation. Remarkably few have actually explored how the brain manages to map and co-ordinate itself, that is, how it actually works.
My research focusses on learning more about visual maps, especially how they interact with attention and memory. Both are central to actual perception; for example, as you read this line you "see" the ones above and below, but ignore them; and if you close your eyes you'll find it hard to recall items around the paper or screen you read this from.
To find visual maps I use an fMRI (functional Magnetic Resonance Imaging) scanner to obtain 3D images of brain activity through time, while volunteers perform a visual task. In one such task, participants look at a computer screen split into sectors, each sector filled with a pattern of waves changing in shape with time and disappearing. Their job is to pay attention to and then remember the patterns in some places while ignoring the rest. Then, I extract two different results. One contains the hot spots of activation during the attention and memory periods. The other, using a fairly new technique, finds chunks of brain where the pattern, not the general level, of activity, varies depending on the spatial location of stimulation.
In this way, I found that the occipital cortex, in the back of the head, showed much map-like activity when volunteers both paid attention to the visual stimuli and kept them active in memory. Interestingly, during the memory period the maps in occipital cortex were not active overall, but only subtly changed their pattern of activation. On the other hand, maps in parietal cortex, at the top and back of the brain, could be detected only during the attention period. Curiously, these same areas showed very high activation during memory, despite displaying no map-like responses.
The benefit of this increased knowledge becomes clear when we look at cases of brain damage that result in some form of visual deficit. Patients with blindsight are effectively blind, but can learn to navigate the environment. Visual neglect, on the other hand, affects attention such that patients can "see" but simply don't notice things happening in half of their visual field. Individuals with optic ataxia can describe how objects look, but find it impossible to interact with them. In contrast, those with visual agnosia are unable to name or describe objects, but can grasp them perfectly.
Many such syndromes can be better understood and treated if we know the precise properties of both the damaged and intact visual maps. We could guide rehabilitation by taking advantage of the plasticity of the brain. We might, thus, stimulate the activity of intact visual maps that communicate with the damaged ones, helping reactivate and regenerate them. This research hints at ways we might "encourage" brain cortexes to do this.
Even as my results add to our knowledge, though, they raise more questions. Why do brain areas sometimes act as maps and other times not? How do maps work when they are inactive? Much work remains to be done, but many benefits remain to be reaped. Still, one thing we can say for certain: there's much more to vision than meets the eye.
Look. The world before you seems simple. It almost appears as though, somewhere inside your head, a cinema projector displays what your eyes capture and interpret. But that's not how we function. Instead, your brain is a cartographer, housing on its cortex a multitude of sensory, mostly visual, maps. Like regular maps, brain maps are drawn in a continuous and fluid way. Just as neighbouring countries are placed adjacent on a map, neurones that respond to similar visual locations are also grouped together.
Depending on the task at hand, our brains pick the best map to get the job done. When we talk about the Earth, depending on the context we interpret it in terms of political, geographical or weather maps, each with its rules and highlights. Just like a map maker, the brain interprets the world surrounding us by simplifying it: it splits it into categories, uses landmarks, and traces frontiers.
Over a dozen maps have recently been found in humans, spread about the brain's cortex. Some maps detect the edges and corners that delineate the outlines of objects. Others only take heed of movement or colour. Another few just seem to predict where you'll soon lay your eyes. Still others are centred on where your eyes are pointed, or relate to the position of your head or hands.
So, that variety is fascinating, but what does this add to science? Well, much of current brain science focusses on labelling a particular brain region with some function. Research programmes often try to find the "centre" for, say, envy, face perception or motivation. Remarkably few have actually explored how the brain manages to map and co-ordinate itself, that is, how it actually works.
My research focusses on learning more about visual maps, especially how they interact with attention and memory. Both are central to actual perception; for example, as you read this line you "see" the ones above and below, but ignore them; and if you close your eyes you'll find it hard to recall items around the paper or screen you read this from.
To find visual maps I use an fMRI (functional Magnetic Resonance Imaging) scanner to obtain 3D images of brain activity through time, while volunteers perform a visual task. In one such task, participants look at a computer screen split into sectors, each sector filled with a pattern of waves changing in shape with time and disappearing. Their job is to pay attention to and then remember the patterns in some places while ignoring the rest. Then, I extract two different results. One contains the hot spots of activation during the attention and memory periods. The other, using a fairly new technique, finds chunks of brain where the pattern, not the general level, of activity, varies depending on the spatial location of stimulation.
In this way, I found that the occipital cortex, in the back of the head, showed much map-like activity when volunteers both paid attention to the visual stimuli and kept them active in memory. Interestingly, during the memory period the maps in occipital cortex were not active overall, but only subtly changed their pattern of activation. On the other hand, maps in parietal cortex, at the top and back of the brain, could be detected only during the attention period. Curiously, these same areas showed very high activation during memory, despite displaying no map-like responses.
The benefit of this increased knowledge becomes clear when we look at cases of brain damage that result in some form of visual deficit. Patients with blindsight are effectively blind, but can learn to navigate the environment. Visual neglect, on the other hand, affects attention such that patients can "see" but simply don't notice things happening in half of their visual field. Individuals with optic ataxia can describe how objects look, but find it impossible to interact with them. In contrast, those with visual agnosia are unable to name or describe objects, but can grasp them perfectly.
Many such syndromes can be better understood and treated if we know the precise properties of both the damaged and intact visual maps. We could guide rehabilitation by taking advantage of the plasticity of the brain. We might, thus, stimulate the activity of intact visual maps that communicate with the damaged ones, helping reactivate and regenerate them. This research hints at ways we might "encourage" brain cortexes to do this.
Even as my results add to our knowledge, though, they raise more questions. Why do brain areas sometimes act as maps and other times not? How do maps work when they are inactive? Much work remains to be done, but many benefits remain to be reaped. Still, one thing we can say for certain: there's much more to vision than meets the eye.
