High-definition Transcranial Direct Current Stimulation Targeting Different Brain Regions Leads to Differential Effects on Cognitive Functions and Event-related Potentials in Patients with Primary Progressive Aphasia
Hsueh-Sheng Chiang1, Christine Dugas2, Paulina Devora2, Katelyn Lucas-Mendoza2, Christine Abasi2, Ashna Adhikari2, Alexander Frolov3, Trung Nguyen3, Brendan Kelley3, John Hart3
1Beth Israel Deaconess Medical Center, 2The University of Texas at Dallas, 3UT Southwestern Medical Center
Objective:
We investigated how high-definition transcranial direct current stimulation (HD-tDCS) targeting separate brain regions could change cognitive performance and brain responses in primary progressive aphasia (PPA) as a novel approach of intervention.
Background:
Cognitive functions are often impaired in PPA. However, most of the existing studies focus on alleviating speech/language symptoms. There have been no studies so far examining how HD-tDCS may change non-speech/language cognition along with brain responses measured by electroencephalography (EEG).
Design/Methods:
This was an open-label study entailing 10 sessions of active HD-tDCS in eight PPA patients (age = 73.4 ± 3.6, 2 F), targeting the left inferior frontal gyrus (LIFG, n = 4) or pre-supplementary motor area (preSMA, n = 4). All underwent baseline and post-treatment evaluations with a neuropsychological battery (immediately and 8 weeks post) and EEG Go-NoGo tasks (immediately post). Midline N200/P300 event-related potential (ERP) components were calculated for EEG. Raw scores from neuropsychological and ERP measures were evaluated using mixed 2 x 2 ANOVAs.
Results:
For immediate effects, the LIFG group improved significantly in working memory (p = 0.035) compared to the preSMA group (p = 0.391). Both groups improved in non-verbal learning (p = 0.015) and processing speed (p = 0.004), but not in attention, verbal learning or executive function (all ps > 0.05). These immediate effects were sustained at 8-week post-treatment. For ERP, there was a significant post-treatment decrease of P300 amplitude (NoGo – Go) in the LIFG group (p < .001), qualitatively more similar to normal controls at post-treatment testing, while no significant change was found in the pre-SMA group (p = .976).
Conclusions:
The present research shows preliminary evidence to support traditional and alternate stimulation sites to treat cognitive deficits other than speech/language in individuals with PPA and informs future designs of non-invasive brain stimulation in treating cognitive symptoms in PPA.
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