Enhancing Letter-Speech Sound Learning and Reading Network Activation With Transcranial Electrical Stimulation

This study investigates the effects of transcranial electrical stimulation (tES) on the brain and its potential to enhance reading-related learning. Adult participants with a range of reading abilities will receive transcranial random noise stimulation (tRNS) while they perform an artificial orthography learning task. This task simulates letter-speech sound learning, an important first step during reading acquisition known to be impaired in individuals with developmental dyslexia. The effects of the intervention will be assessed using both behavioral measures and functional magnetic resonance imaging (fMRI).

This study investigates the effects of transcranial electrical stimulation (tES) on the brain and its potential to enhance reading-related learning. The aim is to identify novel techniques for treating developmental dyslexia, which is a common learning disorder that occurs in childhood and can persist into adulthood. Typically, standard therapy for dyslexia consists of specific reading exercises; however, such training often does not fully remediate the difficulties. This study, therefore, evaluates how transcranial electrical stimulation may be applied to support learning and ultimately reading. During the stimulation, participants perform an artificial orthography learning task simulating letter-speech sound learning. Whereas previous tES reading studies have focused primarily on behavioral outcomes, the present study additionally measures brain activity using fMRI to elucidate how tES affects neural processing and how these effects may relate to reading abilities. The knowledge gained from this project is intended to support the future development of transcranial electrical stimulation as an intervention for adults and children with developmental dyslexia.

Inclusion Criteria: * Age 18-35 * All genders * Written informed consent by the participant * German speaking (native) * Right-handed Exclusion Criteria: * Diagnoses of neurological disorders, intellectual disabilities, or psychiatric disorders (We do not exclude participants with common comorbidities of dyslexia, specifically dyscalculia, Attention Deficit/Hyperactivity Disorder, or Autism Spectrum Disorders) * History of any acquired brain damage or evidence of fetal alcohol syndrome * Hearing problems and vision problems that cannot be corrected * Inability to follow procedures or understand the instructions given in (Swiss-)German * Current use of psychoactive medications or substances, or a history of substance abuse that may affect brain function, performance or MRI signal quality * A nonverbal IQ \< 80 * Having previously participated in a transcranial electrical stimulation study * Knowledge to read or write in a language using foreign letters (i.e., different from the Latin alphabet) * Contraindications to brain stimulation or MRI, such as: History of epilepsy or severe migraine; Skull breach such as craniotomy; Wearing neurostimulators or cardiac pacemakers; Wearing hearing aid devices or cochlear implants, which are not MR safe; Having metal pieces in their body (e.g., piercings that cannot be removed and contain metal, screws or plates from surgical operations, wounds from metal splinters or similar); Claustrophobia or problems lying in the scanner (e.g., pain, anxiety); Previous surgery on the head or heart; Being pregnant (a pregnancy test will be conducted at the MR center before the measurement if a female participant suspects she might be pregnant or is uncertain about her pregnancy status according to the Swiss Ethics Leitlinie: https://swissethics.ch/assets/pos\_papiere\_leitfaden/20110906\_kek\_mri.pdf); Having problems lying still (strong cold, tremor, etc.); Wearing non-removable dental braces