Neural substrates of the cognitive processes underlying spelling: Evidence from MR diffusion and perfusion imaging

Background: Despite a rich literature on the cognitive processes underlying spelling, there is little known about the neural substrates of these processes. Aims: The study aimed to identify regions of brain dysfunction associated with impairment of each cognitive process underlying spelling. It was hypothesised that impairments of distinct components of the spelling task would be associated with different areas of low blood flow or infarction in acute stroke patients. Methods & procedures: Associations between impairment of each component of the spelling process and hypoperfusion and/or infarct of any of 11 Brodmann's areas (BAs) were identified in a consecutive series of 80 patients studied within 24 hours of onset of left hemisphere stroke. Impairment of each component of spelling was identified with tests of written naming, word comprehension, spelling words and pseudowords to dictation, direct and delayed copying, and case transcoding. Infarct and/or hypoperfusion in each BA was identified with MR diffusion-weighted imaging and perfusion-weighted imaging. Significant associations were identified with a correlation matrix, and the strongest associations were confirmed with chi square analysis. Outcomes & results: Impairments of various cognitive processes were associated with separate regions of tissue dysfunction. Conclusions: It was concluded that spelling involves a network of relatively independent processes that rely on different brain regions.