The Vision Group logo incorporates a fractal network known as a "chexagon." Chexagon is the fanciful shorthand for "cortical hexagons," a conjectured structure for visual processing in the human brain. For more extensive discussion of chexagons, consult the following papers:

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A hexagonal orthogonal-oriented pyramid as a model of image representation in visual cortex (1989)
Andrew B. Watson & Albert J. Ahumada Jr., IEEE Transactions on Biomedical Engineering 36(1), 97-106.
An orthogonal oriented quadrature hexagonal image pyramid (1987)
Andrew B. Watson & Albert J. Ahumada Jr., NASA Technical Memorandum 100054.
Recursive, in-place algorithm for the hexagonal orthogonal oriented quadrature image pyramid (1989)
Andrew B. Watson,Proceedings of the SPIE 1099, 194-200.

High resolution postscript drawing of the chexagon.
Math Mathematica Notebook for drawing chexagons.