Dyslexia
Conditions
Brief summary
This study aims at investigating the role of low-gamma activity in phonemic encoding and its implication in dyslexia. Indeed, a phonological deficit, i.e. a difficulty in perceiving the sounds of speech, is strongly suspected in dyslexia but has never been conclusively associated with a specific underlying mechanism. The study employs transcranial alternating current stimulation in adults with and without dyslexia to exploit the effect of the stimulation on phonemic processing and neural activity measured with electroencephalography. In doing so, it would be possible to establishing a causal link between gamma oscillations and the phonological deficit in dyslexia.
Interventions
DEVICETranscranial alternating current stimulation
Focal transcranial stimulation over auditory cortex by means of 5 electrodes delivering an electric current (max. 2mA). In addition to active stimulation, also a placebo (sham) stimulation is employed as a control condition. All subjects included in the study receive all tACS stimulation conditions.
Sponsors
Wyss Center for Bio and Neuroengineering
University of Geneva, Switzerland
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Masking description
One of three different tACS conditions is administered to all participant during three experimental days. The conditions differ in the frequency of stimulation (condition 1 and 2) and in whether the stimulation is active or faked (sham). The order of the three stimulation conditions is counterbalanced across participants, who are not aware of which tACS condition they are undergoing.
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* 18-65 years old; * French native speakers; * normally-hearing; * intellectual quotient (IQ) around average; * for the dyslexia group: previous diagnosis of dyslexia as assessed by a speech therapist.
Exclusion criteria
* Presence of metal or electronic implants in the brain/skull; * Presence of metal or electronic device at other in other parts of the body; * Have experienced a seizure or a loss of consciousness or a severe head trauma; * Severe brain related illness ; * Intake of central nervous system-effective medication; * Pregnant and nursing women; * Relatives affected by epilepsy.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Measure low-gamma neural oscillations with electroencephalography recordings | 6 hour | Auditory-steady state responses to auditory stimuli are measured to assess specific differences between individuals with dyslexia and normo-readers, and between the different tACS stimulation conditions before, after and 1h after the 20 min. tACS stimulation. These neural correlated are estimated by considering the power of EEG signal at the frequency used to modulate the auditory stimuli. |
| Changes in linguistic performance through a battery of behavioral tests | 6 hours | Measurement of phonemic and syllabic processing (pseudoword repetition and spoonerism test), and reading (reading a 3 min. text, both accuracy and reading speed are considered) skills. These tests are repeated before, after and 1h after the tACS stimulation. |
Countries
Switzerland
Outcome results
None listed