Changes in DTI Diffusivity and fMRI Connectivity Cluster Coefficients for Students with and without Specific Learning Disabilities In Written Language: Brain's Response to Writing Instruction.

Abstract

Before and after computerized writing instruction, participants completed assessment with normed measures and DTI and fMRI connectivity scanning. Evidence-based differential diagnosis was used at time 1 to assign them to diagnostic groups: typical oral and written language (n=6), dysgraphia (impaired handwriting, n=10), dyslexia (impaired word spelling and reading, n=20), and OWL LD (impaired syntax construction, n=6). The instruction was aimed at subword letter writing, word spelling, and syntax composing. With p <.001 to control for multiple comparisons, the following significant findings were observed in academic achievement, DTI (radial diffusivity RD, axial diffusivity AD, and mean diffusivity MD), and graph cluster coefficients for fMRI connectivity. A time effect (pre-post intervention increase) in handwriting and oral construction of sentence syntax was significant; but diagnostic group effects were significant for dictated spelling and creation of word-specific spellings, with the dyslexia and OWL LD groups scoring lower than the typical control or dysgraphia groups. For RD a time effect occurred in anterior corona radiata and superior frontal. For AD a time effect occurred in superior corona radiata, superior frontal region, middle frontal gyrus, and superior longitudinal fasciculus. For MD a time effect occurred in the same regions as AD and also anterior coronal radiata. A diagnostic group effect occurred for graph cluster coefficients in fMRI connectivity while writing the next letter in alphabet from memory; but the diagnostic group × time interaction was not significant. The only significant time × treatment interaction occurred in right inferior frontal gyrus associated with orthographic coding. Compared to time 1, cluster coefficients increased at time 2 in all groups except in the dysgraphia group in which they decreased. Implications of results are discussed for response to instruction (RTI) versus evidence-based differential diagnosis for identifying students with SLDs in writing which may be best understood at both the behavioral and brain levels of analysis.