The graphemic/motor frontal area Exner's area revisited

• Published in: Annals of neurology Vol. 66; no. 4; pp. 537 - 545
• Main Authors: Roux, Franck-Emmanuel, Dufor, Olivier, Giussani, Carlo, Wamain, Yannick, Draper, Louisa, Longcamp, Marieke, Démonet, Jean-François
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-10-2009; Wiley-Liss; Wiley
• Subjects: Adult; Behavioral psychophysiology; Biological and medical sciences; Brain Mapping - methods; Cognitive science; Electric Stimulation - methods; Female; Frontal Lobe - physiology; Fundamental and applied biological sciences. Psychology; Handwriting; Hormones and behavior; Humans; Magnetic Resonance Imaging - methods; Male; Medical sciences; Middle Aged; Motor Cortex - physiology; Neurology; Neuroscience; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Young Adult; Frontal; Nervous system diseases
• ISSN: 0364-5134; 1531-8249
• DOI: 10.1002/ana.21804

Objective
In 1881, Exner first described a “graphic motor image center” in the middle frontal gyrus. Current psycholinguistic models of handwriting involve the conversion of , orthographic representations into motor representations before a sequence of appropriate hand movements is produced. Direct cortical stimulation and functional magnetic resonance imaging (fMRI) were used to study the human frontal areas involved in writing.
Methods
Cortical electrical stimulation mapping was used intraoperatively in 12 patients during the removal of brain tumors to identify the areas involved in oral language (sentence reading and naming) and writing, and to spare them during surgery. The fMRI activation experiment involved 12 right‐handed and 12 left‐handed healthy volunteers using word dictation (without visual control) and 2 control tasks.
Results
Direct cortical electrical stimulation of restricted areas rostral to the primary motor hand area (Brodmann area [BA] 6) impaired handwriting in 6 patients, without disturbing hand movements or oral language tasks. In 6 other patients, stimulation of lower frontal regions showed deficits combining handwriting with other language tasks. fMRI also revealed selective activation during word handwriting in left versus right BA6 depending on handedness. This area was anatomically matched to those areas that affected handwriting on electrical stimulation.
Interpretation
An area in middle frontal gyrus (BA6) that we have termed the graphemic/motor frontal area supports bridging between orthography and motor programs specific to handwriting. Ann Neurol 2009;66:537–545