A system for drawing and drawing-related neuropsychology

Abstract

Drawing and copying are complex synthetic activities. They can be based on visual inputs (designs, pictures, or objects) that are present while the subject is drawing or that are removed after exposure so that the drawer depends on temporary memory. Alternatively, the inputs may depend on speech and evoke longer-term visual representations. This account develops a model that combines the perceptual and the linguistic/semantic routes in a system that has as its output a sequence of graphic processing modules. In outlining this system, I draw on data from normal and brain-impaired subjects and explore a series of special problems: (1) What use can we make of a sequence from 2D, 2½D, and 3D perceptual analysis? (2) What sort of buffer do we need that acts as a work-space for the read-out of visual representations, and in particular, can we assume that it is an imagery buffer? (3) What is the structure of the knowledge system we use when drawing from long-term object representations? (4) What are typical depiction decisions and processes involved in drawing from object perception or visual representations? (5) What relation might there be between deficits in drawing and copying on the one hand and manual gesture on the other? This article also describes some new graphic tasks that can help to fractionate further the mechanisms of graphic construction.