The National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health, is looking for individuals to participate in clinical studies. Participating in clinical trials allows you to play an active role in research on the nature and causes of many disorders of the brain and nervous system, and to possibly help physician-scientists develop future treatments. The information below is designed to help you quickly learn about actively recruiting research studies for which you or someone you know may be eligible.


Objectives Developmental dyscalculia (DD) is a condition in which subjects cannot process adequately numerical concepts. Performance of arithmetical calculations is associated with fMRI activity in an extended brain network that includes parietal and prefrontal cortices. Areas within the parietal lobe, required for numerical processing in healthy subjects, are abnormal in subjects with DD. The purpose of this single-blinded study is to determine if facilitatory transcranial direct current stimulation (tDCS) of these parietal areas in association with numerical training will improve processing of numerical information relative to sham in subjects with DD and in healthy volunteers. Study population 30 healthy volunteers and 30 subjects with developmental dyscalculia (DD). Design Healthy volunteers and subjects with DD will be randomly assigned to one of two groups. Each group will receive anodal tDCS or sham with numerical training. All subjects will participate in 7 sessions. First, they will be trained on an ordinal numerical task (numerical training task) in which they will learn the magnitude relations between two numbers on 6 consecutive days while receiving sham stimulation or tDCS during the training. Subjects will see two numbers on the screen, one viewed on the left side of the screen and the other on the right side of the screen (example, 2, 4), and they have to decide which one is larger. Performance will be evaluated by fitting a power-law function. Before the beginning of the experiment and after each training day subjects will perform a numerical Stroop task that assesses the automaticity of numerical processing, and a number-space task that will provide information on the subject's accuracy of mapping numbers into space. At the end of each of the 6 training days (immediately post training) and 3 months (seventh session) later (retention measure) subjects will be tested on a dyscalculia test (The Dyscalculia Screener),the numerical Stroop task, and the number-space task Outcome Measures The primary outcome measure will be the improvement in automatic numerical processing (numerical Stroop task) as reflected by reaction times. Secondary outcomes are accuracy when mapping numbers into space (number-space task) and improvement in the dyscalculia score (Dyscalculia Screener).

Eligibility Criteria:

- INCLUSION CRITERIA: We will include healthy volunteers and DD subjects who meet the following criteria: Age 18 to 50 years Able to provide informed consent No history of math difficulties as determined by Dyscalculia Screener examination > upper 50th percentile (healthy volunteers) Diagnosed with DD and scored 75 (dexterity) or LI of less than -75 (left-handedness) EXCLUSION CRITERIA: We will exclude healthy volunteers and DD subjects if one of the following conditions applies: Unable to perform the tasks due to visual problems History of seizures or brain tumor History of alcohol or drug abuse (defined as the use of a drug for a nontherapeutic effect ) or psychiatric illness such as severe depression History of brain surgery Drug treatment acting primarily on the central nervous system, which lowers the seizure threshold such as antipsychotic drugs (chlorprozamine, clozapine). Pregnancy

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