An adaptive semantic matching paradigm for reliable and valid language mapping in individuals with aphasia

Abstract

Research on neuroplasticity in recovery from aphasia depends on the ability to identify language areas of the brain in individuals with aphasia. However, tasks commonly used to engage language processing in people with aphasia, such as narrative comprehension and picture naming, are limited in terms of reliability (test-retest reproducibility) and validity (identification of language regions, and not other regions). On the other hand, paradigms such as semantic decision that are effective in identifying language regions in people without aphasia can be prohibitively challenging for people with aphasia. This paper describes a new semantic matching paradigm that uses an adaptive staircase procedure to present individuals with stimuli that are challenging yet within their competence, so that language processing can be fully engaged in people with and without language impairments. The feasibility, reliability and validity of the adaptive semantic matching paradigm were investigated in sixteen individuals with chronic post-stroke aphasia and fourteen neurologically normal participants, in comparison to narrative comprehension and picture naming paradigms. All participants succeeded in learning and performing the semantic paradigm. Test-retest reproducibility of the semantic paradigm in people with aphasia was good (Dice coefficient = 0.66), and was superior to the other two paradigms. The semantic paradigm revealed known features of typical language organization (lateralization; frontal and temporal regions) more consistently in neurologically normal individuals than the other two paradigms, constituting evidence for validity. In sum, the adaptive semantic matching paradigm is a feasible, reliable and valid method for mapping language regions in people with aphasia.

Keywords: aphasia; language mapping; reliability; validity.

© 2018 Wiley Periodicals, Inc.

Figures

Figure 1

Methodological details. (a) Example semantic item. This item is a match, and is shown surrounded by a box that appears when the “match” button is pressed (the box confirms the button press, but no information on accuracy is provided). (b) Example perceptual item. This item is a mismatch, so the button should not be pressed. (c) An illustration of how the Dice coefficient of similarity captures the extent of overlap between two thresholded images. (d) Regions of interest in a representative participant and projected onto the lateral surfaces of a template brain. ROI 1 (Brain) encompassed the whole brain. ROI 2 (Supra) encompassed regions shown in red, green or blue. ROI 3 (Lang+) corresponded to regions shown in red or green. ROI 4 (Lang) is shown in red

Figure 2

Behavioral data for the adaptive semantic matching paradigm. Accuracy, item difficulty, and reaction time on the semantic and perceptual control conditions in individuals with aphasia and neurologically normal participants. Perc = Perceptual

Figure 3

Language activation maps derived from the adaptive semantic matching paradigm. (a) Group analysis in 14 neurologically normal participants. Whole brain activations were thresholded at voxelwise p < .005 then corrected for multiple comparisons at p < .01 based on cluster extent. (b) Activation maps in 16 individuals with aphasia at two time points each. The patients are arranged in groups according to clinical impression, then in ascending order of overall QAB score within each group. See Participants section, and for more detailed language data, see Figure 14 of Wilson et al. (2018), which is laid out the same way. Voxels with the highest 5% of t statistics were plotted, subject to a minimum cluster volume of 2 cm3, in an ROI comprising known language regions or plausible candidate regions for functional reorganization (Lang+ ROI); note that the cerebellum was not included (unlike panel a). Inset axial slices show lesion reconstructions. T1 = first imaging session; T2 = second imaging session; Dice = Dice coefficient of similarity; LI = lateralization index

Figure 4

Language activation maps derived from the narrative comprehension paradigm. (a) Group analysis in 14 neurologically normal participants. (b) Activation maps in 4 of the 16 individuals with aphasia at two time points each. These 4 patients are the 4 patients in the third row of Figure 3. See Figure 3 caption for additional definitions and explanations

Figure 5

Language activation maps derived from the picture naming paradigm. (a) Group analysis in 14 neurologically normal participants. (b) Activation maps in 4 of the 16 individuals with aphasia at two time points each. These 4 patients are the 4 patients in the third row of Figure 3. See Figure 3 caption for additional definitions and explanations

Figure 6

Psychometric assessment of the three paradigms. (a) Test–retest reproducibility of the three paradigms in individuals with aphasia. The distribution of the Dice coefficient is plotted (relative voxelwise threshold = 5%; minimum cluster volume = 2 cm3; ROI = Lang+, that is language regions and plausible candidates for reorganization). (b) Lateralization of language maps. The distribution of the lateralization index is plotted for neurologically normal individuals, and for individuals with aphasia, for each of the three paradigms. Individuals with apparent right hemisphere language dominance are indicated with black dots (NN14 and A12). (c) Sensitivity for detection of dominant hemisphere frontal language area. The distribution of the activation volume in the dominant inferior frontal gyrus is plotted for neurologically normal individuals, and for individuals with aphasia, for each of the three paradigms. (d) Sensitivity for detection of dominant hemisphere temporal language area. The distribution of the activation volume in the temporal ROI is plotted for neurologically normal individuals, and for individuals with aphasia, for each of the three paradigms

Figure 7

Impact of analysis parameter sets. (a) Impact of analysis parameters on test–retest reproducibility of the three paradigms in individuals with aphasia. Mean Dice coefficients of similarity across participants are plotted as a function of absolute and relative voxelwise thresholds (y axes), region of interest (x axes) and minimum cluster volume (x axes). Regions of interest: Brain = whole brain; Supra = supratentorial cortical regions; Lang+ = known language regions and plausible candidates for reorganization; Lang = known language regions and their homotopic counterparts. White outlines indicate parameter sets that exemplified desirable psychometric properties across the board (Dice ≥ 0.60; LI ≥ 0.60; frontal and temporal regions detected without fail in the neurologically normal group). Thick black outlines show the a priori analysis parameter set. (b) Impact of analysis parameters on language lateralization in neurologically normal participants. Mean lateralization indices across participants are plotted for each paradigm as a function of absolute and relative voxelwise thresholds (y axes), region of interest (x axes) and minimum cluster volume (x axes). (c) Impact of analysis parameters on language lateralization in individuals with aphasia

Figure 8

Language activation maps derived from the adaptive semantic matching paradigm in 14 neurologically normal individuals. See Figure 3 caption for more information

Figure 9

Revised adaptive semantic matching paradigm. (a) Accuracy, item difficulty, and reaction time on the revised semantic and perceptual control conditions in a second group of 16 neurologically normal participants. Perc = Perceptual. (b) Group analysis in this neurologically normal group. Whole brain activations were thresholded at voxelwise p < .005 then corrected for multiple comparisons at p < .01 based on cluster extent