Thought representation can be divided into enactive, image, and lexical modes. Each system of representation has intrinsic organizational properties, although organizational formats developed with acquisition of one mode can be used in all other modes. Ordinarily, there is free translation of information between systems of representation. Neurological or psychological pathology may interfere with specific representational capacity or freedom of translation between modes of representation. By postulating controls at the boundaries of representational systems, one can specify the cognitive operations involved in defensive mechanisms. Use of the proposed model would allow precise description of conscious experience, especially of such global terms as "regression."