Interhemispheric and Intrahemispheric Connectivity From the Left Pars Opercularis Within the Language Network Is Modulated by Transcranial Stimulation in Healthy Subjects

Abstract

Neural activity related to language can be modulated within widespread networks following learning or in response to disruption-including the experimental application of noninvasive brain stimulation. However, the spatiotemporal characteristics of such modulation remain insufficiently explored. The present study combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to explore the modulation of activity across the language network following continuous theta-burst stimulation (cTBS) of the left pars opercularis. In 10 healthy subjects (21 ± 2 years old, four females), neuronavigated cTBS was delivered over the left pars opercularis of the frontal operculum (part of the traditional Broca's area) at 80% of active motor threshold (AMT) stimulation intensity. Real cTBS and sham cTBS were performed in two different visits separated by at least 48 h. Before, immediately, and 10 min after cTBS, 30 single pulses of TMS were delivered to the left pars opercularis at 80% of the resting motor threshold (RMT), whereas EEG was simultaneously recorded. We examined the cTBS-induced modulation of phase locking values (PLVs) between the TMS-evoked potentials (TEPs) recorded over the pars opercularis and those recorded over its right-hemispheric homolog area, the left supramarginal area, and the left superior temporal area in different EEG frequency bands and different time windows following cTBS. cTBS to the left pars opercularis induced within the gamma band: (1) a significant increase in TEP phase synchronization between the left and right pars opercularis at an early time window (250-350 ms) following cTBS; and (2) significantly increased PLV with the left supramarginal area and the left superior temporal area at a later time window (600-700 ms). In the theta and delta band, cTBS to Frontiers in Human Neuroscience | www.frontiersin.org 1 March 2020 | Volume 14 | Article 63 Yoo et al. Language Network Modulation by cTBSthe left pars opercularis induced significantly increased phase synchronization of TEPs between the left pars opercularis and the posterior left hemispheric language areas at a late time window. In sham condition, there was a significant decrease in TEP phase synchronization of the high beta band between left pars opercularis and left superior temporal area at 200-300 ms. These results contribute to characterize the dynamics of the language network and may have implications in the development of noninvasive stimulation protocols to promote the language rehabilitation in aphasia patients.

Continuous theta burst stimulation-induced suppression of the right fronto-thalamic-cerebellar circuit accompanies improvement in language performance in poststroke aphasia: A resting-state fMRI study

“…In addition to traditional speech and language therapy (SLT), repetitive transcranial magnetic stimulation (rTMS), one of the most promising noninvasive brain stimulation (NIBS) modalities, has emerged as an ideal method to improve the language function of patients with PSA ( Ren et al, 2014 ; Kapoor, 2017 ; Gholami et al, 2022 ). rTMS can modulate the excitability and activity of targeted cortical regions, thereby promoting the reorganization of functional networks ( Kapoor, 2017 ; Yoo et al, 2020 ; Jargow et al, 2021 ). Continuous theta burst stimulation (cTBS) is a novel rTMS method that reduces excitability.…”

“…A recent study showed that cTBS over the right pars triangularis of individuals with chronic PSA enhanced word retrieval by facilitating phonological access ( Harvey et al, 2019 ). Yoo et al (2020) delivered neuronavigated cTBS over the left pars opercularis in healthy subjects, resulting in significantly increased phase synchronization of TMS-evoked potentials (TEPs) in language areas between the two hemispheres and within the left hemisphere. These results may have implications for the development of a cTBS protocol to assist language rehabilitation in patients with PSA.…”

Systemic Review on Transcranial Electrical Stimulation Parameters and EEG/fNIRS Features for Brain Diseases

“…Brain stimulation has been widely applied due to its ability to modulate brain plasticity in neuropsychiatric patients ( Davis and Smith, 2019 ; Kim E. et al, 2020 ; Yoo et al, 2020 ). Typically, brain stimulation methods have been classified as invasive or noninvasive brain stimulation (NIBS).…”