Neuronatomical Correlates of Spelling and Writing: Steven Z. Rapcsak and Pelagie M. Beeson
The first descriptions of writing impairment following focal brain damage appeared during the second half of the nineteenth century. A particularly important early contribution was the report of Ogle (1867), which explicitly argued for the anatomical independence of writing from speech based on clinical observations of a double dissociation between agraphia and aphasia. This paper also introduced the first classification system of agraphia by drawing a critical distinction between linguistic impairments of spelling and motor disorders of writing. The publication of Ogle's seminal work was soon followed by attempts to localize the brain regions involved in various aspects of the writing process. These efforts culminated in the development of neuroanatomical models that postulated two distinct cortical writing centers. Following Dejerine's suggestion (1891), it was generally assumed that orthographic information relevant to the correct spelling of familiar words was stored in the dominant angular gyrus. In addition, Exner (1881) postulated the existence of a cortical center responsible for controlling the skilled movements of handwriting located at the foot of the second frontal convolution. Although the putative writing centers were conceptualized as being physically separate from the cortical speech areas identified by Broca and Wernicke, this neuroanatomical arrangement did not always imply complete functional independence. In fact, many theorists considered written expression to be parasitic upon speech and maintained that it necessarily required phonological mediation. In particular, some investigators proposed that writing involved subword-level phonological-to-orthographic transcoding (that is, phoneme-grapheme conversion) (Grashey, 1885; Wernicke, 1886), whereas others believed that orthographic representations for familiar words could be activated only indirectly via the spoken form of the word (Wernicke, 1874; Dejerine, 1914). However, there were also those who considered writing an autonomous Ian-
guage skill that depended on the coordinated activity of the parietal and frontal writing centers without the obligatory participation of the cortical speech areas (Charcot, 1883; Pitres, 1894; Bastian, 1897).