Normal writing processes and peripheral acquired dysgraphias

The cognitive operations involved in writing may be divided for convenience into central and peripheral processes. Central processes include semantic, syntactic and other sentence-level operations, along with those processes responsible for either retrieving from memory the spelling of a familiar word or assembling from sound a plausible spelling for an unfamiliar word or nonword. The end-product of these central processes is an abstract graphemic representation of words as letter strings. Peripheral writing processes translate that abstract graphemic representation into a range of possible output modes, including handwriting, typing, and spelling aloud. A model of peripheral writing processes is presented, concentrating on the processes responsible for creating handwritten output. A number of different peripheral acquired dysgraphias including mirror writing are then reviewed and interpreted in terms of impairment at different levels in the conversion of abstract graphemes into written letters and words.