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

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.

• Sham iTBS (Device): Placebo stimulation for the iTBS group
• Sham cTBS (Device): Placebo stimulation for the cTBS group
• intermittent theta burst stimulation (iTBS) (Device): Excitatory theta burst stimulation
• continuous theta burst stimulation (cTBS) (Device): inhibitory theta burst stimulation

Primary outcomes

• RTs for Picture Naming With the Factors Language (L1, L2) and Block (Switching, Non-Switching) [Within 30 minutes after intervention]: 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.

Secondary outcomes

• Nonverbal Switching [Within 30 minutes after intervention]: Nonverbal Switching: response times

Sex: All, ages: 18 Years to 45 Years, accepts healthy volunteers

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

Participant flow

Outcome results

• RTs for Picture Naming With the Factors Language (L1, L2) and Block (Switching, Non-Switching) (Primary), Mean, Milliseconds: RTs for PN After Intermittent Theta Burst Stimulation 1103.32 +/- 126; RTs for PN After Continuous Theta Burst Stimulation 1107.26 +/- 131; RTs for Picture Naming in L1 1098.82 +/- 405; RTs for Picture Naming in L2 1158.91 +/- 432; RTs for Picture Naming in the Non-switching Blocks 1081.14 +/- 414; RTs for Picture Naming in the Switching Blocks 1175.24 +/- 420 (p 0.932)
• Nonverbal Switching (Secondary), Mean, Milliseconds: Intermittent Theta Burst Stimulation 772.07 +/- 159.28; Continuous Theta Burst Stimulation 739.32 +/- 137.23 (p 0.642)

Adverse events

Time frame: 3 hours

Other adverse events by term

• Holtzheimer P, Fawaz W, Wilson C, Avery D. Repetitive transcranial magnetic stimulation may induce language switching in bilingual patients. Brain Lang. 2005 Sep;94(3):274-7. doi: 10.1016/j.bandl.2005.01.003. PMID 16098377
• Lefaucheur JP, Andre-Obadia N, Antal A, Ayache SS, Baeken C, Benninger DH, Cantello RM, Cincotta M, de Carvalho M, De Ridder D, Devanne H, Di Lazzaro V, Filipovic SR, Hummel FC, Jaaskelainen SK, Kimiskidis VK, Koch G, Langguth B, Nyffeler T, Oliviero A, Padberg F, Poulet E, Rossi S, Rossini PM, Rothwell JC, Schonfeldt-Lecuona C, Siebner HR, Slotema CW, Stagg CJ, Valls-Sole J, Ziemann U, Paulus W, Garcia-Larrea L. Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS). Clin Neurophysiol. 2014 Nov;125(11):2150-2206. doi: 10.1016/j.clinph.2014.05.021. Epub 2014 Jun 5. PMID 25034472
• Nardone R, De Blasi P, Bergmann J, Caleri F, Tezzon F, Ladurner G, Golaszewski S, Trinka E. Theta burst stimulation of dorsolateral prefrontal cortex modulates pathological language switching: A case report. Neurosci Lett. 2011 Jan 10;487(3):378-82. doi: 10.1016/j.neulet.2010.10.060. Epub 2010 Oct 29. PMID 21036201

• Study Protocol and Statistical Analysis Plan (PDF, 2016-06-06)

• Jean-Marie Annoni, Prof. Dr., Principal investigator, University of Fribourg