Chapter 37: alexia and agraphia

Studies of alexia and agraphia have played important roles in understanding how complex cognitive functions are related to brain structure and activity. Modern interests in brain-behavior relations began during the second half of the 19th century as an outgrowth of flawed correlative studies by neuroanatomist Franz Gall and subsequent clinical-pathological analyses by Jean-Baptiste Boulliaud on speech and the frontal lobes. In 1856, Louis Victor Marcé drew attention to writing disorders and postulated a cerebral faculty for writing. Following Paul Broca's epochal reports on aphemia, many European physicians investigated reading and writing impairments after brain injury. Albert Pitres published the first detailed description of isolated agraphia, and Adolf Kussmaul identified alexia as an isolated symptom of brain disease. Jules Dejerine in 1892 provided the first clinical-pathological descriptions of pure alexia, and he suggested a key role for the left parietal lobe in reading and writing. In the 20th century, varieties of agraphia or alexia were linked to apraxia (Hugo Liepmann), impaired body image (Josef Gerstmann), spatial misperception, and interhemispheric disconnection. Other analyses focused on error types that defined new clinical syndromes (e.g. deep dyslexia) and provided evidence for cognitive modularity.