Some are smeared, and some are spots

[mmcirvin]

Classic hallucinations explained as normal modes of a differential equation describing propagating excitations in the visual cortex. A couple of papers on the subject are linked here.

Comments

[mmcirvin.livejournal.com]

...Also, one of the things they stress in the papers is that the spiral and tunnel patterns come from the fact that the cells in the visual cortex seems to map to visual angle with something similar to a complex logarithm. That right there immediately explains why Escher hyperbolic tesselations and the paisley spirals in the Mandelbrot set have such a powerful hippie attraction: it's all conformal mapping, dude!