Tracking neuromodulation effects in logopenic primary progressive aphasia: A proof-of-concept single-case study using multidimensional speech biomarkers

Background Conventional standardized assessments often fail to capture subtle but clinically meaningful language changes following neuromodulation in logopenic primary progressive aphasia (lvPPA), creating a critical need for more sensitive monitoring tools such as speech biomarkers. Aims This study evaluates speech biomarkers for monitoring neuromodulation effects in lvPPA, specifically examining whether multidimensional speech analysis can be linked to tDCS (transcranial direct current stimulation) -induced changes that complement traditional assessment methods. Methods & procedures : Using a randomized double-blind cross-over design, we administered both active and sham tDCS targeting the dorsolateral prefrontal cortex in a single lvPPA patient with Alzheimer’s disease underlying pathology. Speech analyses were conducted across naming, repetition, and narrative tasks during four longitudinal assessment phases. These speech analyses complemented standardized valid tests of tDCS targets : executive functions and naming capabilities. Outcomes & Results : Speech Analyses revealed clinically meaningful improvements in speech parameters following active stimulation, including reduced latency times, elimination of phonological paraphasias, and increased lexical diversity. Acoustic markers showed enhanced prosodic features and vocal quality. These speech changes aligned with improvements in executive functions, suggesting shared neurocognitive mechanisms. Conclusions While these promising findings warrant confirmation in larger cohorts, they provide preliminary evidence that multidimensional speech analysis offers a sensitive tool for tracking neuromodulation outcomes in neurodegenerative language disorders, potentially enhancing the assessment of therapeutic interventions beyond the limitations of traditional standardized measures.