Through Thick and Thin: Baseline Cortical Volume and Thickness Predict Performance and Response to Transcranial Direct Current Stimulation in Primary Progressive Aphasia

Abstract

ObjectivesWe hypothesized that measures of cortical thickness and volume in language areas would correlate with response to treatment with high-definition transcranial direct current stimulation (HD-tDCS) in persons with primary progressive aphasia (PPA).Materials and MethodsIn a blinded, within-group crossover study, PPA patients (N = 12) underwent a 2-week intervention HD-tDCS paired with constraint-induced language therapy (CILT). Multi-level linear regression (backward-fitted models) were performed to assess cortical measures as predictors of tDCS-induced naming improvements, measured by the Western Aphasia Battery-naming subtest, from baseline to immediately after and 6 weeks post-intervention.ResultsGreater baseline thickness of the pars opercularis significantly predicted naming gains (p = 0.03) immediately following intervention, while greater thickness of the middle temporal gyrus (MTG) and lower thickness of the superior temporal gyrus (STG) significantly predicted 6-week naming gains (p’s < 0.02). Thickness did not predict naming gains in sham. Volume did not predict immediate gains for active stimulation. Greater volume of the pars triangularis and MTG, but lower STG volume significantly predicted 6-week naming gains in active stimulation. Greater pars orbitalis and MTG volume, and lower STG volume predicted immediate naming gains in sham (p’s < 0.05). Volume did not predict 6-week naming gains in sham.ConclusionCortical thickness and volume were predictive of tDCS-induced naming improvement in PPA patients. The finding that frontal thickness predicted immediate active tDCS-induced naming gains while temporal areas predicted naming changes at 6-week suggests that a broader network of regions may be important for long-term maintenance of treatment gains. The finding that volume predicted immediate naming performance in the sham condition may reflect the benefits of behavioral speech language therapy and neural correlates of its short-lived treatment gains. Collectively, thickness and volume were predictive of treatment gains in the active condition but not sham, suggesting that pairing HD-tDCS with CILT may be important for maintaining treatment effects.

Transcranial Direct Current Stimulation in neurogenetic syndromes: new treatment perspectives for Down syndrome?

“…A combined approach with tDCS and cognitive and behavioral training appears to be more effective than stimulation alone (Cappelletti et al, 2013 ; Martin et al, 2014 ; Mancuso et al, 2016 ). Strengthening or weakening activation patterns via Hebbian synaptic mechanisms of neuroplasticity, as suggested neural mechanisms of tDCS, can be selectively reinforced by external stimulation, such as cognitive training, speech therapy, motor, attention, and WM training (Jones et al, 2015 ; Wang et al, 2018 ; Boroda et al, 2020 ; Nissim et al, 2020 , 2022 ). For this reason, we suggest potential frameworks and approaches for the practical implementation of tDCS projects in DS that combine tDCS and cognitive and behavioral training, aimed at improving cognition and behavior.…”

“…The potential of this approach lies in its ability to improve functioning by addressing altered E/I balance and neuroplasticity (Bavelier et al, 2010 ). By strengthening or weakening activation patterns through Hebbian synaptic mechanisms of neuroplasticity, tDCS may modulate external stimulation, such as cognitive, speech and motor training, selectively reinforcing their effects (Jones et al, 2015 ; Wang et al, 2018 ; Boroda et al, 2020 ; Nissim et al, 2020 , 2022 ).…”

Baseline functional connectivity predicts who will benefit from neuromodulation: evidence from primary progressive aphasia

“…Recent studies from different groups, including our own, have identified several baseline factors that predict efficacy of tDCS for a given patient or patient group [see [6][7][8] for reviews]. Five predictive factors have been identified: (1) baseline language and cognitive performance [9,10], (2) baseline cortical volume and thickness [11][12][13], (3) baseline white matter integrity [14], (4) clinical variant PPA [15], and (5) baseline sleep efficiency [16]. To our knowledge, no studies have utilized baseline functional brain connectivity as a predictor of tDCS effects in PPA.…”