Temporospatial identification of language‐related cortical function by a combination of transcranial magnetic stimulation and magnetoencephalography

Abstract

IntroductionIdentification of language-related cortical functions can be carried out noninvasively by transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG), which allow for lesion-based interrogation and global temporospatial investigation of cortices, respectively. Combining these two modalities can improve the accuracy of the identification, but the relationships between them remain unclear. We compared TMS and MEG responses during the same language task to elucidate their temporospatial relationships and used the results to develop a novel method to identify language-related cortical functions.MethodsTwelve healthy right-handed volunteers performed a picture-naming task during TMS and MEG. TMS was applied on the right or left inferior frontal gyrus (IFG) at five time points, and the reaction times (RTs) for naming the pictures were measured. The temporospatial oscillatory changes measured by MEG during the same task were then compared with the TMS results.ResultsTranscranial magnetic stimulation of the left IFG significantly lengthened RTs at 300 and 375 msec after picture presentation, whereas TMS of the right IFG did not change RTs significantly. Interestingly, the stimulus time point at which RTs increased significantly for each individual was correlated with when the low gamma event-related desynchronizations (ERDs) peaked in the left IFG. Moreover, combining the results of TMS and MEG improved the detection rate for identifying the laterality of language function.ConclusionsThese results suggest that the low gamma ERDs measured by MEG strongly relate to the language function of picture naming in the left IFG. Finally, we propose a novel method to identify language-related cortical functions by combining TMS and MEG.

The role of the supplementary motor area for speech and language processing

“…However, in case of higher-order language functions the motor system might not necessarily be activated. In this case, speech reaction time may serve as a behavioral measure for testing TMS-induced modulation of brain functions (Shinshi et al, 2015). Various studies investigated therapeutic aspects of inhibitory or facilitatory brain stimulation during stroke rehabilitation.…”

Adaptive Plasticity in the Healthy Language Network: Implications for Language Recovery after Stroke

“…In another recent study, Shinshi and colleagues [118] used TMS and MEG to investigate the role of the left pIFG in picture naming. In a first experiment, the authors showed that high-frequency 40 Hz triple pulse TMS over the left pIFG but not right pIFG significantly delayed naming latencies when applied 300 or 375 ms after picture presentation.…”

Non-Invasive Brain Stimulation to Investigate Language Production in Healthy Speakers: A Meta-Analysis

“…Subsequent TMS studies have further established a direct relation between the left anterior temporal lobe (ATL; Pobric, Jefferies, & Lambon Ralph, 2007, left middle temporal gyrus (MTG; Acheson, Hamidi, Binder, & Postle, 2011;Schuhmann, Schiller, Goebel, & Sack, 2012), and left IFG (Schuhmann, Schiller, Goebel, & Sack, 2009;Shinshi et al, 2015;Wheat et al, 2013) in picture naming. Of note, event-related single-and triple-pulse TMS studies have provided a more finegrained picture with respect to the temporal dynamics of picture naming, locating the involvement of the IFG at around 300 ms after picture onset, whereas MTG and STG may function as a feed-forward monitoring system around this time point.…”

“…Cortical activity during this task has been located in a large left frontotemporal network stretching from the interior frontal to posterior superior temporal and inferior parietal regions (Indefrey, 2011;Indefrey & Levelt, 2004). Using TMS, which applies an ultra-short electromagnetic pulse that creates an electric current in superficial cortical nerve tissue, an engagement of the posterior superior temporal gyrus (pSTG), middle temporal gyrus (MTG), anterior temporal lobe (ATL), and inferior frontal gyrus (IFG) has been demonstrated (Acheson, Hamidi, Binder, & Postle, 2011;Mottaghy et al, 1999;Pobric, Jefferies, & Lambon Ralph, 2007, 2010, Schuhmann, Schiller, Goebel, & Sack, 2009Shinshi et al, 2015;Sparing et al, 2001;Töpper, Mottaghy, Brügmann, Noth, & Huber, 1998;Wheat et al, 2013). Furthermore, cortical excitability can be modulated by applying a constant weak electric current between two electrodes affixed on the scalp.…”

“…Of note, event-related single-and triple-pulse TMS studies have provided a more finegrained picture with respect to the temporal dynamics of picture naming, locating the involvement of the IFG at around 300 ms after picture onset, whereas MTG and STG may function as a feed-forward monitoring system around this time point. In spite of these effects, only half of the studies were sham-controlled (Schuhmann et al, 2009;Shinshi et al, 2015;Wheat et al, 2013), leaving open the possibility that the observed TMS effects are confounded by procedural effects. In addition, it remains unclear why the first studies targeting pSTG yielded a naming advantage (i.e., shorter naming latencies) while the other studies in fact reported slower naming latencies, both for STG, but also for IFG, MTG, and ATL stimulation.…”