Dyslexia, Dyslexia, Developmental, Learning; Developmental Disorder, Reading
Conditions
Keywords
word learning, consolidation, vocabulary, artificial lexicon, brain stimulation, transcranial magnetic stimulation
Brief summary
The purpose of the proposed study is to use transcranial magnetic stimulation (TMS) to evaluate a neurobiological model of spoken word learning in older youth. Specifically, it is hypothesized that: (1) inhibition of the left dorsal stream will impact subsequent learning, processing, and retention of phonologically similar pseudowords; (2) the impact of dorsal stream inhibition on word learning will be associated with baseline levels of variability in neural activity, indicative of underlying differences in cortical excitability.
Detailed description
The proposed study is designed to assess the contribution of the dorsal stream of the language network (i.e., left supramarginal gyrus, or SMG) to different aspects of novel word learning in two groups of participants (16-24 years of age): 20 typically developing older youth (OYTD; tested in Aim 1) and 20 older youth with reading difficulties (OYRD; tested in Aim 2). The investigators will use inhibitory continuous theta burst stimulation (cTBS), a well-established repetitive TMS (rTMS) protocol that reduces cortical excitability in a targeted brain region for up to 60 minutes. Participants will complete a baseline magnetic resonance imaging (MRI) session in Week 1, followed by cTBS or sham stimulation to the left SMG, with order of administration counterbalanced across participants. Immediately following cTBS (or sham), participants will complete a visual pseudoword phonological discrimination task and a spoken word learning task. The following day (i.e., 24 hours later), retention of items learned will be measured. In Week 2, cTBS (or sham) will be administered to the left SMG (whichever stimulation was not administered in Week 1) and then the pseudoword discrimination and word learning tasks will be administered using a different set of novel words from those presented in Week 1. Twenty-four hours later, the retention of this second set of items will be measured.
Interventions
OTHERActive cTBS
Active stimulation
OTHERSham
Control stimulation
Sponsors
Georgia State University
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Eligibility
Sex/Gender
ALL
Age
16 Years to 24 Years
Healthy volunteers
Yes
Inclusion criteria
* Native English speaker (who is not fluent in any other language and does not identify as bilingual) * Normal or corrected to normal vision
Exclusion criteria
* Diagnosed with Autism Spectrum Disorder * Hearing deficits (\>25 decibels at 500+ Hz), visual deficits (\>20/40), serious emotional problems (e.g., severe, uncontrolled depression) and certain neurological conditions (e.g., uncontrolled seizure disorders) * Individuals with certain metals in their bodies or with certain health conditions. If an individual has braces on their teeth, a cardiac pacemaker; hearing aid; other metal in their body or eyes (which may include certain metallic-embedded tattoos), including but not limited to pins, screws, shrapnel, plates, dentures or other metal objects * Individuals taking certain medications that lower seizure threshold * Individuals with TMS Screening and Contraindication Forms which do not pass TMS Tech review * Individuals with MRI Screening and Contraindication Forms which do not pass MRI Tech review
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Novel Word Learning Task | 5-mins post stimulation; 24hrs post stimulation | The spoken word learning task, completed post-cTBS, will consist of a two-alternative forced choice paradigm in which participants will be presented with two pictures of unusual objects, and will be asked to indicate via button press which picture matches a spoken label. Initial trials require a pure guess, with feedback provided on each trial, and continued until a correct answer is given. Across six learning blocks (24 trials each), participants will learn a set of eight pseudowords total. Twenty-four hours following the initial learning task, participants will be asked to complete two additional learning blocks which will be used to assess retention accuracy. Over the course of the experiment, participants will learn two different sets of items, counter-balanced across participants and groups. |
| Pseudoword Discrimination Task | Immediately following cTBS | The visual pseudoword discrimination task is a computerized forced-choice, reaction time assessment of phonological processing. It measures the participants' ability to phonetically decode a string of letters. This task is simple with high accuracy and has proven highly sensitive to individual differences in phonological decoding skills. Participants are asked to judge via button press whether a visually presented letter string can be pronounced like a 'real word' or not. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| MRI Scan | baseline | Pre-rTMS MRI scans will consist of anatomical and functional sequences consistent with well-established protocols in the field designed to assess baseline properties and functioning of the reading and language network. The functional MRI (fMRI) Picture Identification task is simple with high accuracy and has proven highly sensitive to individual differences in reading skills. Participants are asked to indicate via button press whether a target stimulus (written or spoken word) matches a picture cue. The fMRI Fast Localizer task rapidly presents sets of four words that vary based on orthographic, phonological, or semantic properties. Anatomical scans are necessary for localizing brain regions targeted for cTBS. |
Countries
United States
Outcome results
None listed