What and Where

18″ X 24″, Ink and 12K gold on stainless steel
scratch holography

This painting was commissioned by The Center for the Neural Basis of Cognition to commemorate Carnegie Award recipient Dr. Leslie Ungerleider’s substantial contribution to the field of vision science.  Her work in delineating the dorsal and ventral visual processing pathways led to the discovery that the ventral pathway predominantly processes information related to how we recognize objects (what), whereas the dorsal pathway interprets how objects are related to one another in space (where).  The painting is designed to reflect this dichotomy in its layout and conceptual content.  The lower, or “ventral” half of the painting depicts a field of black pyramidal neurons on a white gold background, providing a simple stimulus to engage the object recognition circuitry of the viewer’s ventral pathway.  In contrast, the upper, or “dorsal” half of the painting depicts a holographic, three-dimensional field of neurons designed to highlight spatial relationships, engaging the viewer’s dorsal pathway in the process.  Thus, the viewer recruits the appropriate “what vs. where” processing circuitry in order to perceive the two halves of the painting.

Scratch Holography Demonstration:

What and Where final from Greg Dunn on Vimeo.

Scratch holograms are created by etching semicircular, two dimensional arcs into stainless steel or other smooth surfaces.  Each pixel of an object is translated into a two dimensional polar coordinate.  When an entire field of these arcs are etched and lit from above using a hard, point light source, the tiny reflections made off of the scratches combine to form a pattern of reflected light that appears to be at a different depth than the surface of the painting.  Varying the radii of these arcs allows the pixel to have greater or lesser depth, giving the illusion that there is a three dimensional space contained somewhere within the painting.  Much like the raw visual data coming in from the retina must be transformed into a perception in later stages of cortical processing, a scratch hologram when perceived under normal room light appears as nothing more than fine scratches on metal, requiring specific processing and lighting conditions in order to reveal the meaning hidden within.

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