Figure 1.

Flowchart detailing the process by which study participants were recruited, grouped, and assessed in the current study, as well as study-specific measures that form the basis of study results. CBS = corticobasal syndrome; CVC = consonant–vowel–consonant; DDK = diadochokinesis; HC = healthy controls; lvPPA = logopenic variant primary progressive aphasia; nfvPPA = nonfluent variant primary progressive aphasia; PPA = primary progressive aphasia; PPAOS = primary progressive apraxia of speech; PSPs = progressive supranuclear palsy syndrome; SIT = Speech Intelligibility Test; SLP = speech-language pathologist; WAB-R = Western Aphasia Battery–Revised. ^aInitial syndrome diagnoses (e.g., PPAOS, nfvPPA) and subgroupings (MSI+, MSI−) are treated as the diagnostic ground truth in the current study and are maintained even in cases where subsequent study-specific analyses—either quantitative speech measures and/or blinded auditory-perceptual ratings—did not agree with these initial designations.