Letter selection and letter assembly in acquired dysgraphia.

OBJECTIVE We explored the constituents of the graphemic buffer in a patient with acquired dysgraphia and tested the hypothesis that the graphemic buffer is composed of 2 dissociable components: letter selection and letter assembly. BACKGROUND Research on dysgraphia has established the graphemic buffer as a component of the spelling mechanism, and the buffer is considered a short-term memory store that is critical for letter production. However, little is known about the components within the buffer. METHOD We devised 2 spelling tasks that rely differentially on letter selection and letter assembly. In the selection task, our patient produced the letters that composed a target word, but she did not have to provide serial position information. In the assembly task, B.H. was given all the letters of a target word and was asked to spell the word by arranging the letters in the proper serial order. RESULTS Compared to spelling to dictation, our patient did not benefit from being given letter identity information (ie, assembly task), but her performance improved significantly when position information was available (ie, selection task). CONCLUSIONS Based on these data, and the comparison of her performance with another dysgraphic patient, we propose that the graphemic buffer engages in both letter selection and letter assembly.