Fig. 6: Group-averaged saliency maps.

a Montage in the first row shows mean Grad-CAM++ saliency for patients correctly predicted by the CNN to have severe aphasia (purple to yellow) and their lesion overlap in percentage units (white to dark green) superimposed on a normalized template (neuroradiological convention). Montage in the second row shows mean deep SHAP saliency maps for patients correctly predicted by the CNN to have severe aphasia. Negative SHAP values were replaced with zeros to reflect feature contributions only towards the class predicted by the model. Brighter yellow colors reflect higher feature importance and darker purple colors reflect greater overlap of lesions in the patient cohort. The alpha channels for lesion overlap and mean saliency are modulated by the respective values of those maps to highlight differences between maps. b Identical to (a) but this montage shows mean Grad-CAM++ saliency for patients correctly predicted by the CNN to have nonsevere aphasia. c Identical to previous panels but the montage shows mean SHAP saliency for patients correctly predicted by the SVM to have severe aphasia. d Identical to previous panels but the montage shows mean SHAP saliency for patients correctly predicted by the SVM to have nonsevere aphasia.