Baseline Performance Predicts tDCS-Mediated Improvements in Language Symptoms in Primary Progressive Aphasia

Abstract

Primary Progressive Aphasia (PPA) is a neurodegenerative condition characterized by insidious irreversible loss of language abilities. Prior studies suggest that transcranial direct current stimulation (tDCS) directed toward language areas of the brain may help to ameliorate symptoms of PPA. In the present sham-controlled study, we examined whether tDCS could be used to enhance language abilities (e.g., picture naming) in individuals with PPA variants primarily characterized by difficulties with speech production (non-fluent and logopenic). Participants were recruited from the Penn Frontotemporal Dementia Center to receive 10 days of both real and sham tDCS (counter-balanced, full-crossover design; participants were naïve to stimulation condition). A battery of language tests was administered at baseline, immediately post-tDCS (real and sham), and 6 weeks and 12 weeks following stimulation. When we accounted for individuals’ baseline performance, our analyses demonstrated a stratification of tDCS effects. Individuals who performed worse at baseline showed tDCS-related improvements in global language performance, grammatical comprehension and semantic processing. Individuals who performed better at baseline showed a slight tDCS-related benefit on our speech repetition metric. Real tDCS may improve language performance in some individuals with PPA. Severity of deficits at baseline may be an important factor in predicting which patients will respond positively to language-targeted tDCS therapies.Clinicaltrials.gov ID: NCT02928848

Electrical brain stimulation in different variants of primary progressive aphasia: A randomized clinical trial

“…Although studies [13,[16][17][18][19][20][21] provide proof-of-concept for the efficacy of tDCS in PPA, these small studies do not yet provide sufficient evidence for sustainability of gains and generalization to untreated items. One difficulty in studying tDCS efficacy in PPA is its phenotypic diversity.…”

Meta-Analysis on the Effects of Transcranial Direct Current Stimulation on Naming of Elderly with Primary Progressive Aphasia

“…Six studies, except one study [23], described the procedure of random allocation in the methodology section. While conducting studies, three studies [24][25][26] blinded researchers and four studies [24,[26][27][28] blinded subjects. Six studies [23][24][25][26][27][28], except for [29], described the measurement methods and evaluation tools in detail.…”

“…However, only one study [25] conducted a power test before starting the experiment. Additionally, only two studies controlled confounding variables [24,28].…”

Online cathodal transcranial direct current stimulation to the right homologue of Broca's area improves speech fluency in people who stutter

“…In particular, positive effects on speech production and word retrieval on non‐fluent type of stroke aphasia have been reported by several tDCS studies that involved either BA or WA as a stimulation site . Significant tDCS effects have been identified also in primary progressive aphasia by showing facilitatory word retrieval . Some of these studies have been successful in retaining the facilitatory effects over several weeks or even months after stimulation periods .…”

“…Significant tDCS effects have been identified also in primary progressive aphasia by showing facilitatory word retrieval . Some of these studies have been successful in retaining the facilitatory effects over several weeks or even months after stimulation periods . Nonetheless, the effects of tDCS on language in aphasia patients may be variable among studies.…”