Targeting Language-specific and Executive-control Networks With Transcranial Direct Current Stimulation in Logopenic Variant PPA

The investigators will assess any changes in performance from pre- to post-treatment and 1- and 3- month follow-up intervals in percent accuracy on word repetition with no delay. This will be measured using the Temple Assessment of Language and Short-Term Memory (TALSA) Test 3: Word and Non-Word Repetition Test. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%), computing change in outcome in percent difference as well as other arithmetic differences between percentage scores before intervention and each time point after. Increase in scores is considered a benefit. This outcome measure corresponds to Aim 1.

The investigators will assess any changes in performance from pre- to post-treatment and 1- and 3- month follow-up intervals in percent accuracy on word repetition with delay (5-sec). This will be measured using the TALSA Test 3: Word and Non-Word Repetition Test. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%), computing change in outcome in percent difference as well as other arithmetic differences between percentage scores before intervention and each time point after. Increase in scores is considered a benefit. This outcome measure corresponds to Aim 1.

The investigators will assess any changes in performance from pre- to post-treatment and 1- and 3- month follow-up intervals in percent accuracy on word span. This will be measured using the TALSA Test 14: Word and Non-Word Repetition Span Test. The investigators will use the span calculation outlined in the TALSA. Span calculations consist of two numbers: the number of the last list length (LL) passed (e.g., 2 for pairs), and the proportion of correct strings out of the required strings to pass (5) of the next list. The highest spans obtainable for this test is 5.00. Increase in scores is considered a benefit. This outcome measure corresponds to Aim 1.

This sentence repetition task comes from the TALSA (Test 7) with scoring based on percent of words in sentences correctly repeated. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

This sentence repetition task comes from National Alzheimer's Coordinating Center's (NACC) FTLD Module with scoring based on percent of words in sentences correctly repeated. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

The digit span forward is a well-established task that assesses rote immediate verbal memory. Participants are presented with a series of digits and are instructed to repeat the digits in the same order. The investigators will compute the raw score of items correctly repeated (up to 9) and compute change in outcome between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

The visual rhyming test assesses link between phonological and orthographic information. Participants are presented words orthographically only and must indicate whether two words rhyme (e.g., pair-spare). The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

The Northwestern Anagram Test (NAT) assesses accuracy of word order (syntax) in sentence production. Participants assemble individual words cards to create meaningful sentences. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

The Northwestern Assessment of Verbs and Sentences (NAVS) Argument Structure Production Test (ASPT) assesses combination of verbs with arguments in a sentence production task. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

Accuracy in spelling non-words using the Johns Hopkins Dysgraphia battery will be assessed. The investigators will compute the raw score of graphemes correct using a spelling scoring system accounting for additions, substitutions, and deletions, and transform to percent correct (range: 0-100%), computing change in outcome in percent difference before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

The presence and severity of apraxia of speech (AOS) is measured using the Apraxia Battery for Adults-Second Edition (ABA-2), specifically through repeating words of increasing length and complexity and describing pictures. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Decrease in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a near-transfer task (i.e., vSTM related, showing generalization to other vSTM tasks).

Accuracy in spelling words using the Johns Hopkins Dysgraphia battery will be assessed. The investigators will compute the raw score of graphemes correct using a spelling scoring system accounting for additions, substitutions, and deletions, and transform to percent correct (range: 0-100%), computing change in outcome in percent difference before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

The Northwestern Assessment of Verbs and Sentences (NAVS) Sentence Comprehension Test (SCT) assesses comprehension of sentences given multiple types of sentences (e.g., canonical vs. non-canonical). The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

The SOAP: Test of Syntactic Complexity assesses comprehension abilities given 4 syntactic construction types. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%). Subsequently, the investigators will compute change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

The Boston Naming Test is a widely used picture naming test that detects lexical retrieval deficits in the oral modality. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%), computing change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

The Hopkins Assessment of Naming Actions (HANA) assesses picture naming (specifically verbs) in the oral modality. The investigators will compute the raw score of items correct and transform to percent correct (range: 0-100%), computing change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

Category fluency tasks involve generating as many words as possible in one minute for a given semantic category (fruits, animals, vegetables). Scoring will be based on number of words generated per minute. The investigators will compute the raw score of items correct and subsequently the percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

Using picture descriptions (e.g., Cookie Theft image from the Boston Diagnostic Aphasia Examination [BDAE]) and personal/procedural discourse tasks, investigators will obtain representative language samples. The investigators will compute the raw score of content (content information units [CIUs]) and efficiency (proportion of mazes: false starts, pauses) and transform to percent correct (range: 0-100%), computing change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

The N-back task is a well-established task that assesses working memory and working memory capacity. Participants are presented with words in sequence and instructed to reply whether the current word matches the one presented 2 words ago. Scoring will be based on the total number of correct responses (hit rate) minus the number of incorrect responses (false alarm rate). The investigators will compute the change in outcome in percent difference between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

The digit span backward is a well-established task that assesses rote immediate verbal memory and working memory. Participants are presented with a series of digits and are instructed to repeat the digits in the reverse order. The investigators will compute the raw score of items correctly repeated and compute change in outcome between before intervention and each time point after. Increase in score is considered a benefit. This outcome measure corresponds to Aim 1 and is considered a far-transfer task (i.e., unrelated to vSTM, showing generalization to other language & cognitive tasks).

Using resting stage functional MRI (rs-fMRI) investigators will detect activity of various brain regions under a resting/task-negative condition, which will help evaluate functional regional interactions as indicated by the z-correlations between the selected brain area. This outcome measure corresponds to Aim 2.

Using Magnetic Resonance Spectroscopy (MRS) investigators will measure metabolite (GABA) concentrations from select brain regions in international units (IU).