Entoptics

In rock art all over the world you find odd pieces of abstract, usually geometric, patterning - chevrons, spirals, lattices, zig zags, dots, wave forms and so on. In the Aurignacian and Magdalenian caves of southern France and northern Spain, these abstractions are more common at the entrances to the caves than they are further in, where the animal portraits we are familiar with usually appear. In his book The Mind in the Cave, David Lewis-Williams suggests these marks may be understood as entoptic phenomena. Entoptic = within vision. In other words, this imagery 'may originate ... between the eye itself and the cortex of the brain.' He distinguishes two types of entoptic imagery: phosphenes, induced by physical stimulation, such as pressure on the eyeball itself; and form constants which derive from the optic system beyond the eye. There is a spacial relationship between the retina and the visual cortex which means that points close together on the retina, if stimulated, lead to the firing of equivalently placed neurons in the cortex. Lewis-Williams suggests that, when psychotropic substances are taken, as he believes they were by most ancient artists, the usual order of this process is, or can be, reversed so that 'the pattern in the cortex is perceived as the visual percept.' People in this state may see the structure of their own brains.

I was reminded of this recently when Peter Simpson gave me a copy of a small pamphlet he had published with a reproduction of a Colin McCahon drawing on the front. This was going to be the cover of a statement on aesthetics, called On the Nature of Art, written by McCahon and his friend and collaborator, John Caselberg, in the early 1950s but not published until 1999. The drawing has a lighted candle on a table in the foreground, behind which, and to one side, is a kerosene lamp, also lit; the beams of this lamp open out across the drawing to illuminate a piece of rectangular lattice-work which looks just like a piece of entoptic imagery derived from laboratory experiments in human neurology/perception, and also one of those grids you find in rock art. I very much like the idea that those who make art are looking both ways at once, into the brain/mind and out at the world of appearances as well; and that, when we look at the things they have made, we are as it were looking both ways twice: in and out of the artist's brain/mind and simultaneously in and out of our own.