Language Mapping in Aphasia

Abstract

Purpose Recovery from aphasia is thought to depend on neural plasticity, that is, functional reorganization of surviving brain regions such that they take on new or expanded roles in language processing. To make progress in characterizing the nature of this process, we need feasible, reliable, and valid methods for identifying language regions of the brain in individuals with aphasia. This article reviews 3 recent studies from our lab in which we have developed and validated several novel functional magnetic resonance imaging paradigms for language mapping in aphasia. Method In the 1st study, we investigated the reliability and validity of 4 language mapping paradigms in neurologically normal older adults. In the 2nd study, we developed a novel adaptive semantic matching paradigm and assessed its feasibility, reliability, and validity in individuals with and without aphasia. In the 3rd study, we developed and evaluated 2 additional adaptive paradigms-rhyme judgment and syllable counting-for mapping phonological encoding regions. Results We found that the adaptive semantic matching paradigm could be performed by most individuals with aphasia and yielded reliable and valid maps of core perisylvian language regions in each individual participant. The psychometric properties of this paradigm were superior to those of other commonly used paradigms such as narrative comprehension and picture naming. The adaptive rhyme judgment paradigm was capable of identifying fronto-parietal phonological encoding regions in individual participants. Conclusion Adaptive language mapping paradigms offer a promising approach for future research on the neural basis of recovery from aphasia. Presentation Video https://doi.org/10.23641/asha.10257584.

Figure 1.

Structural magnetic resonance imaging of the brain of Mr. L. The left inferior frontal gyrus, much of the middle frontal gyrus, the ventral precentral gyrus, the insula, and underlying white matter were completely destroyed, yet Mr. L experienced an excellent long-term recovery from his aphasia.

Figure 2.

Reliability and validity of four language mapping paradigms in a representative neurologically normal individual. Activations within potential language regions or their homotopic counterparts are depicted in the hot color scale, whereas activations elsewhere are depicted in yellow. Adapted from “Validity and reliability of four language mapping paradigms,” by S. M. Wilson, A. Bautista, M. Yen, S. Lauderdale, & D. K. Eriksson, 2017, NeuroImage: Clinical, 16, p. 404. Copyright © 2017 Elsevier. Adapted with permission. ROI = region of interest.

Figure 3.

Adaptive semantic matching paradigm. (A) Example of a semantic item. This item is a match and is shown surrounded by a box that appears when the “match” button is pressed. (B) Example of a perceptual item. This item is a mismatch, so the button should not be pressed. Adapted from “An adaptive semantic matching paradigm for reliable and valid language mapping in individuals with aphasia,” by S. M. Wilson, M. Yen, & D. K. Eriksson, 2018, Human Brain Mapping, 39, p. 3288. Copyright © 2018 John Wiley and Sons. Adapted with permission.

Figure 4.

Language activation maps derived from the adaptive semantic matching paradigm. (A) Group analysis in 14 neurologically normal participants. (B) Activation maps in 16 individuals with aphasia at two time points each. Voxels with the highest 5% of t statistics were plotted, subject to a minimum cluster volume of 2,000 mm³, in a region of interest comprising known language regions or plausible candidate regions for functional reorganization; note that the cerebellum was not included (unlike in Panel A). Inset axial slices show lesion reconstructions. T1 = first imaging session; T2 = second imaging session; Dice = Dice coefficient of similarity; LI = lateralization index. Adapted from “An adaptive semantic matching paradigm for reliable and valid language mapping in individuals with aphasia,” by S. M. Wilson, M. Yen, & D. K. Eriksson, 2018, Human Brain Mapping, 39, p. 3296. Copyright © 2018 John Wiley and Sons. Adapted with permission.

Figure 5.

Activation maps derived from group analyses of neurologically normal participants for (A) the rhyming judgment paradigm, (B) the syllable counting paradigm, and (C) the semantic matching paradigm. Note that the left supramarginal gyrus and the left ventral precentral gyrus were activated only by the phonological paradigms. Adapted from “Adaptive paradigms for mapping phonological regions in individual participants,” by M. Yen, A. T. DeMarco, & S. M. Wilson, 2019, NeuroImage, 189, p. 374, Copyright © 2019 Elsevier. Adapted with permission.

Figure 6.

Functional magnetic resonance imaging of the brain of Mr. L. (A) Core language regions identified by the adaptive semantic matching paradigm. (B) Phonological encoding regions identified by the adaptive rhyming judgment paradigm. Activations were thresholded at t > 3.5, with an arbitrary minimum cluster size of 1,000 mm³.