The inner eye of Two Cultures

Marina Warner, as a student of art and literature, is stimulated and challenged.

Possessors of the evil eye, according to the ancient magical concept, threw a malignant influence on the object of their gaze; in modern Italian, they are known as iettatori , from Latin iacere , to hurl or throw. The belief was connected to the Platonic idea that the eyes issued "species" that interacted dynamically with the field of vision, and that perception was consequently active. Medusa, the most extreme case, literally fascinated her victims - she bound them, like a bundle of sticks, by merely casting an eye on them. The notion that modesty required women to lower their eyes arose from fear of these species-projectiles, and of their erotic power over poor unfortunate males who might come into view.

All of these notions have of course been tossed onto the rubbish heap of superstition a long time ago, and vision has been understood to result from receptive imaging on the retina, processed by the brain. The model of the eyeball connected to a screen on which pictures are projected, upside down, and are then correctly "read" by mental powers, was taught in my biology O-level classes in the early 1960s, and still largely obtains.

Semir Zeki, professor of neurobiology at the University of London, is not of course a believer in the petrifying powers of the gaze or in mal'occhio , nor does he show interest in these fantasies of visual folklore, but he does revolutionise the conventional view of the passive eye in favour of a dynamic, generative concept of vision. Inner Vision sets out, with admirable lucidity, clear diagrams and splendid colour plates, that "Vision... is an active process, not the passive one that we have for long imagined it to be", and that several aspects of visual experience - colour above all - do not inhere in natural phenomena, but result from the brain's interpretation of data. "We see in order to know," Zeki writes, and, in seeing, we form our experience of phenomena. Claude Monet, for example, sorted out through sheer intensity of attention the different wavelengths of light on the facade of Rouen cathedral and thereby created unsurpassed studies in the mutability of colour playing on the same form. The function of "the creative process [of seeing] ..." Zeki continues, "constitutes an extension of the function of the visual brain".

However, we can interact with the world as beheld only to the limits of our brain power; we cannot go beyond them - in some unsettling sense, the physical properties of the world are constituted by our powers of perception, and slip out of representations of reality when our brain cells cannot apprehend them. Bees are sensitive to ultra-violet light, for example, but it is invisible to human eyes; there are consequently no UV paintings. This might seem obvious, but the implications are less so: if the limits of vision in some way define the limits of knowledge, then extending vision will break through those borders.

By drawing on artists' adventures in representing the world as it offers itself to the eye, Zeki journeys through the mind's labyrinthine byways along several different tracks. First, he is interested in the stimuli that pictures and sculptures produce in the brain, and specifically in different pockets and cells in and around the primary visual cortex; he summarises some extremely absorbing evidence from experiments of the past 25 years. As anyone is aware who has known the victim of a stroke or an accident, some faculties survive, while others are destroyed, depending on the specific locality of the lesion in the brain; as a result, terrible, distressing conditions such as the inability to recognise faces (prosopagnosia) or sudden total colour blindness have contributed hugely to the mapping of consciousness and vision on to cerebral anatomy. A patient who was afflicted with akinetopsia (blindness to motion) could not even pour a cup of tea because she could not see the level of the liquid rise in the cup. Not only do colour, form, movement, orientation, angle and other aspects of visual information light up different bulbs in the head, as it were, but they do so at different speeds. The advances in detailed knowledge of the brain's working are astonishing; they have the effect of making the phrenologists, with their exact compartmentalisations of powers and affects, look oddly prescient.

In his attempt to connect brain science to human beings' unusually developed desire to make images, Zeki relates recent findings of neurobiology to aesthetics and, indeed, wonders if "one might be able to develop the outlines of a theory of aesthetics that is biologically based". He argues that many artists, especially when breaking with representational tradition, are - unknowingly - working with the image-processing systems of the mind: "Most painters are also neurologists," he writes, "they are those who have experimented upon and, without ever realising it, understood something about the organisation of the visual brain." Thus, when Alexander Calder eliminated colour from his mobiles, or at least simplified it to black, white and red, he instinctively grasped that motion impinges more forcefully - becomes more visible - when not muddled up with lots of different colour signals. Similarly, Kasimir Malevich's experiments with red squares or Mondrian's geometric grids play to the brain's predominance of cells that respond to saturated reds and to vertical and horizontal ordering. In this light, the tangled involutions and profuse, fractal complexities of much "outsider art" begin to look like direct impressions of the mental troubles that the artists often suffer from: unusual psychological states mediated through equally unusual perceptual processing.

Many, many questions still remain, however: about how the brain binds together the data it is processing into a unified picture; about the range of functions many areas perform, such as the intriguingly named "fusiform gyrus", a newly important site of cognition, operative in seeing colours and recognising people (if you cannot put a name to that face, it is your fusiform gyrus that is playing up). Above all, how do the pleasurable sensations excited by a painting rhyme with visual stimuli? Sometimes Zeki's ideas suggest that cognition is in itself a pleasure, a bit like a shiatsu massage of the cerebral nodes. Could Hogarth's "Line of Beauty" possess a biological value? Are redness, squareness, rectilinearity intrinsically satisfying? These possible inferences of Zeki's explorations (he does not himself make them) might lead one back to other discredited pseudo-sciences, Neoplatonist and alchemical syntheses and even onto synaesthetic, semi-mystical theosophical territory and its Rudolf Steinerian dependencies. Mondrian travelled these regions in his perceptual quest, as did Kandinsky who, above all painters, invented a visual language of line, colour and rhythm in order to deliver those aesthetic feelings of wonder and delight that travel through the brain to suffuse all the rest of the beholder and still remain mysterious.

Because vision does not mirror the world but actively constitutes it, art and artists have the potential to extend perception and deepen memory's networks of thoughts. We can accept readily that after looking at a Leonardo drawing (or, better still, copying it), we understand more about the spin on the crest of a wave or the foliage of a star of Bethlehem plant. But what about pressing the boundaries of vision beyond the empirically observable? The artist Adam Lowe and the historian of science, Simon Schaffer, from the department of the history and philosophy of science at Cambridge, have collaborated on "Noise", an exhibition about ways of picturing phenomena that - like atomic particles, the reverberations of the Big Bang, the sound waves of a soprano's voice, and cosmic rays - lie beyond the grasp of the eyes. Some of these adventures in apprehending the invisible are rich and strange indeed, and their very unfamiliarity makes them difficult to "read": here the import of Zeki's argument comes home, for while we all now know from a hundred episodes of Casualty how to read the quivering spurts of a ECT cardiogram, we have to be taught to grasp the meaning of the lovely spirals that spin off the central flow of energy when a "charmed particle" is produced in bubble-chamber photographs of atoms, on display on the walls of Kettle's Yard in Cambridge (until March 26) and the Wellcome Trust Two10 Gallery in London (until 19 May).

The exhibition includes other remarkable exercises in analytic picturing: Margaret Watts Hughes (d. 1907) used a kind of loud-hailer to record her own acoustic vibrations, and thus discovered "Chiadni" effects or those thrilling, changing ring patterns, whorls and ebb ripples that appear in a tray of sand or liquid when you send sound waves through it. Watts Hughes took a remarkable, Leonardoesque step farther, however, and recorded the patterns her singing produced by coating a glass plate and taking an impression of the figures appearing in the medium - she used several varieties of powder and fluids.

Lowe and Schaffer also include examples of brain imaging, by Cat scans and other technological media, such as Zeki relies on to communicate his information, and they draw attention to the images of coded, rather than representational status. (Just in case anyone is wondering, there are no colours in the brain, or indeed any inside the body, in spite of all those amazing iridescent magnified photographs, collected by William A. Ewing, for example, which have endowed the human gut with the baroque efflorescence of the Great Barrier Reef.) "Noise" comes with a catalogue full of surprises, information, useful essays by Bruno Latour and Peter Galison and many others, and is in itself experimentally designed to pleasurable effect, setting the brain cells firing away with colour over-printing, fold-out flaps and original juxtapositions of scientific and artistic endeavours that have, in Zeki's formulation, used vision "to acquire knowledge about this world". For a visitor with no grounding in the sciences, the exhibition needs patient absorption: its heart lies in the novelty and uniqueness of visual languages, many of them richly rewarding precisely because their unfamiliarity opens new pathways of understanding. For this, the catalogue offers an invaluable guide, preferably to be consulted ahead of time.

The interaction of the artistic imagination and scientific inquiry is enjoying unprecedented attention, stimulated in recent times by the inspired, lyrical curiosity of writers such as the late Primo Levi and Miroslav Holub, and today by the fiction and poetry of A. S. Byatt, Lavinia Greenlaw and Robert Crawford. Suggestively, this novel and energetic engagement does not establish science's modes of analysis and perception as true or right in opposition to poetry's or art's; rather, as in the fields of anatomy and botany, where knowledge grew through picturing, the innovatory work of Zeki and the multiple adventures in representation on display in "Noise" reveal that the heuristic poetic activity of the visual cortex, its dynamic engagement with its objects, not only convey but can actively create understanding of the phenomena of physics, medicine, and astronomy that lie far beyond the immediate field of vision.

Marina Warner is the author of No Go the Bogeyman: Scaring, Lulling and Making Mock .