Impact of Theta Burst Stimulation Over the Left DLPFC on Language Switching

Study Overview
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Brief Summary
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The purpose of this study is to investigate whether theta burst stimulation (TBS) over the left dorsolateral prefrontal cortex (DLPFC) influences language switching and cognitive flexibility. The experimental paradigm will assess the impact of inhibitory and excitatory prefrontal stimulation by TBS versus sham-TBS over the DLPFC in healthy bilinguals.

Detailed Description
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Background: Clinical observations and neuroimaging studies seem to confirm the role of executive functions and frontal structures in language processing in bilingual subjects. Repetitive transcranial magnetic stimulation, such as for example theta burst stimulation (TBS), is increasingly being used as a valuable tool for neuroscientists investigating the underlying mechanisms of cognitive functions. Case studies have shown a change in language switching after bilingual patients received repetitive magnetic stimulation to the left DLPFC. However, there is no study investigating the effect of TBS applied to the DLPFC on language switching in healthy participants. Procedure: A planned total of 40 unbalanced bilingual participants will be included. Half of the participants will receive inhibitory theta burst stimulation (continuous TBS), the other half excitatory theta burst stimulation (intermittent TBS). After TBS, different language and nonverbal tasks will be performed while an EEG is measured. Before being stimulated, each subject will conduct the same tasks with a sham-TBS as a baseline measure.

Official Title
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Impact of Theta Burst Stimulation Over the Left Dorsolateral Prefrontal Cortex on Language Switching and Cognitive Flexibility

Conditions
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Languages

Intervention / Treatment
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* Device: Sham iTBS
* Device: Sham cTBS
* Device: intermittent theta burst stimulation (iTBS)
* Device: continuous theta burst stimulation (cTBS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: L1 (Swiss)German, knowledge of English as a foreign language 18-45 years of age right-handedness Exclusion Criteria: epilepsy / family history of epilepsy brain surgery, traumatic brain injuries cardiac pacemaker, metallic objects in the head history of neurological diseases or severe psychiatric disorders drug use (alcohol, psychoactive medication) strong headache pregnancy

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Factorial Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: intermittent theta burst stimulation<br>intermittent theta burst stimulation (iTBS) + Sham iTBS | Device: Sham iTBS<br>* Placebo stimulation for the iTBS group<br>Device: intermittent theta burst stimulation (iTBS)<br>* Excitatory theta burst stimulation<br>|
| Experimental: continuous theta burst stimulation<br>continuous theta burst stimulation (cTBS) + Sham cTBS | Device: Sham cTBS<br>* Placebo stimulation for the cTBS group<br>Device: continuous theta burst stimulation (cTBS)<br>* inhibitory theta burst stimulation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| RTs for Picture Naming With the Factors Language (L1, L2) and Block (Switching, Non-Switching) | Picture naming with the factors Language (L1, L2) and Block (Switching, Non-Switching): Speech onset times (msec) L1 refers to the mother tongue. L2 refers to the late acquired (> age 7) second language. Switching Block refers to a language switching block with picture naming alternated between the mother tongue and the second language. Non-Switching Block refers to a block of picture naming either only in the mother or only in the second language. | Within 30 minutes after intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Nonverbal Switching | Nonverbal Switching: response times | Within 30 minutes after intervention | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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theta burst stimulation, Language switching, dorsolateral prefrontal cortex