The central framework for the project is a double-blind, sham-controlled, crossover study in which subjects with the non-fluent/agrammatic and semantic variants of primary progressive aphasia (naPPA and svPPA, respectively) will undergo language testing and structural and functional brain imaging before and after receiving 10 semi-consecutive daily sessions of real or sham transcranial direct current stimulation (tDCS) paired with modified constraint-induced language therapy (mCILT). Language testing and brain imaging will be repeated immediately after completion of and up-to 24 weeks following completion of treatment.~Subjects with naPPA and svPPA will be randomized to one of two study arms: tDCS+mCILT or sham stimulation+mCILT paired with pre- and post-stimulation imaging and behavioral measures. Equal numbers of subjects with naPPA and svPPA will be randomized to the tDCS + mCILT and sham + mCILT study arms. The study is double-blinded, in that neither the subject nor the study personnel administering tDCS or sham stimulation will know which arm of the study the subject has been randomized into. Study coordinators will administer tDCS by entering a pre-determined code that has been programmed into the device by another member of the study team. Data will be digitally audio-recorded and analyzed off-line, such that study team members performing data coding and analysis will likewise be blinded to the treatment condition of each subject.~Subject participation in this protocol will occur during 36 planned visits that will span approximately 12 months. The events of the study visits are described below:~VISIT 1:~Informed consent and screening~VISIT 2:~Baseline MRI~VISIT 3 & 4:~Baseline language assessment~VISITS 5-14:~tDCS+mCILT OR sham stimulation+mCILT, depending on the study arm to which they had been randomized.~VISIT 15 & 16:~Follow-up language assessment Follow-up MRI~VISIT 17:~6-Week follow-up language assessment~VISIT 18 & 19:~12-week follow-up language assessment 12-week follow-up MRI~**CROSSOVER**~VISIT 20:~Crossover baseline language assessment~VISITS 21-30:~tDCS+mCILT or sham stimulation+mCILT~VISIT 31 & 32:~Follow-up language assessment Follow-up MRI~VISIT 33:~6 Week follow-up language assessment~VISIT 34 & 35:~12-week follow-up language assessment 12-week follow-up MRI~VISIT 36:~24 week follow-up language assessment
This is a double-blind, sham-controlled, crossover study in which subjects with the non-fluent/agrammatic and semantic variants of primary progressive aphasia (naPPA and svPPA, respectively) will undergo language testing and structural and functional brain imaging before and after receiving 10 semi-consecutive daily sessions of real or sham transcranial direct current stimulation (tDCS) paired with modified constraint-induced language therapy (mCILT). Language testing and brain imaging will be repeated immediately after completion of and up-to 24 weeks following completion of treatment. The investigators will examine changes in language performance induced by tDCS + mCILT compared to sham tDCS + mCILT. The investigators will also use network science to analyze brain imaging (fMRI) data to identify network properties associated with baseline PPA severity and tDCS-induced changes in performance. This study will combine knowledge gained from our behavioral, imaging, and network data in order to determine the relative degrees to which these properties predict whether persons with PPA will respond to intervention.