Neuroanatomical correlates of oral reading in acute left hemispheric stroke

Abstract

Oral reading is a complex skill involving the interaction of orthographic, phonological, and semantic processes. Functional imaging studies with nonimpaired adult readers have identified a widely distributed network of frontal, inferior parietal, posterior temporal, and occipital brain regions involved in the task. However, while functional imaging can identify cortical regions engaged in the process under examination, it cannot identify those brain regions essential for the task. The current study aimed to identify those neuroanatomical regions critical for successful oral reading by examining the relationship between word and nonword oral reading deficits and areas of tissue dysfunction in acute stroke. We evaluated 91 patients with left hemisphere ischemic stroke with a test of oral word and nonword reading, and magnetic resonance diffusion-weighted and perfusion-weighted imaging, within 24-48h of stroke onset. A voxel-wise statistical map showed that impairments in word and nonword reading were associated with a distributed network of brain regions, including the inferior and middle frontal gyri, the middle temporal gyrus, the supramarginal and angular gyri, and the middle occipital gyrus. In addition, lesions associated with word deficits were found to be distributed more frontally, while nonword deficits were associated with lesions distributed more posteriorly.

Figure 1

A) Distribution map of lesion location for all patients in the current study. Voxels of the MNI atlas where tissue dysfunction (hypoperfusion and/or dense ischemia or infarct, as defined above) was associated in the continuous analysis with B) overall oral reading impairment (bright red = p < 0.01 FDR, dark red = p < 0.05 FDR), and C) word (red) and nonword (blue) reading impairment, and regions common to both (purple). Images are presented in radiological convention (left hemisphere on right).