scholarly journals Enhancing vs. inhibiting semantic performance with repetitive transcranial magnetic stimulation over the anterior temporal lobe: frequency- and task- specific effects

2019 ◽  
Author(s):  
JeYoung Jung ◽  
Matthew A. Lambon Ralph
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Temporal Lobe ◽  
Magnetic Stimulation ◽  
Semantic Processing ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Semantic Representation ◽  
Healthy Individuals ◽  
Anterior Temporal Lobe ◽  
Specific Effects ◽  
Virtual Lesion

AbstractAccumulating, converging evidence indicates that the anterior temporal lobe (ATL) appears to be the transmodal hub for semantic representation. A series of repetitive transcranial magnetic stimulation (rTMS) investigations utilizing the ‘virtual lesion’ approach have established the brain-behavioural relationship between the ATL and semantic processing by demonstrating that inhibitory rTMS over the ATL induced impairments in semantic performance in healthy individuals. However, a growing body of rTMS studies suggest that rTMS might also be a tool for cognitive enhancement and rehabilitation, though there has been no previous exploration in semantic cognition. Here, we explored a potential role of rTMS in enhancing and inhibiting semantic performance with contrastive rTMS protocols (1Hz vs. 20Hz) by controlling practice effects. Our results demonstrated that it is possible to modulate semantic performance positively or negatively depending on the ATL stimulation frequency: 20Hz rTMS was optimal for facilitating cortical processing (faster RT in a semantic task) contrasting with diminished semantic performance after 1Hz rTMS. In addition to cementing the importance of the ATL to semantic representation, our findings suggest that 20Hz rTMS leads to semantic enhancement in healthy individuals and potentially could be used for patients with semantic impairments as a therapeutic tool.

Neurochemical profiles of the anterior temporal lobe predict response of repetitive transcranial magnetic stimulation on semantic processing

2021 ◽  
Author(s):  
JeYoung Jung ◽  
Stephen Williams ◽  
Faezeh Sanae Nezhad ◽  
Matthew Lambon Ralph
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Temporal Lobe ◽  
Magnetic Stimulation ◽  
Semantic Processing ◽  
Cortical Excitability ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Semantic Representation ◽  
Cortical Region ◽  
Anterior Temporal Lobe ◽  
Neurochemical Profiles

Abstract The effect of repetitive transcranial magnetic stimulation can vary considerably across individuals, but the reasons for this still remain unclear. Here, we investigated whether the response to continuous theta-burst stimulation (cTBS) – an effective protocol for decreasing cortical excitability – related to individual differences in glutamate and GABA neurotransmission. We applied cTBS over the anterior temporal lobe (ATL), a hub for semantic representation, to explore the relationship between the baseline neurochemical profiles in this region and the response to this stimulation. Our experiments revealed that non-responders (subjects who did not show an inhibitory effect of cTBS on subsequent semantic performance) had higher excitatory-inhibitory balance (glutamate + glutamine/GABA ratio) in the ATL, which led to up-regulated task-induced regional activity as well as increased ATL-connectivity with other semantic regions compared to responders. These results disclose that the baseline neurochemical state of a cortical region can be a significant factor in predicting responses to cTBS.

scholarly journals The Timing of Anterior Temporal Lobe Involvement in Semantic Processing

2015 ◽  
Vol 27 (7) ◽  
pp. 1388-1396 ◽  
Author(s):  
Rebecca L. Jackson ◽  
Matthew A. Lambon Ralph ◽  
Gorana Pobric
Keyword(s):  
Temporal Lobe ◽  
Semantic Processing ◽  
Semantic Representation ◽  
Critical Role ◽  
Stimulus Presentation ◽  
Middle Temporal Gyrus ◽  
Anterior Temporal Lobe ◽  
Temporal Pole ◽  
Modal Semantic

Despite indications that regions within the anterior temporal lobe (ATL) might make a crucial contribution to pan-modal semantic representation, to date there have been no investigations of when during semantic processing the ATL plays a critical role. To test the timing of the ATL involvement in semantic processing, we studied the effect of double-pulse TMS on behavioral responses in semantic and difficulty-matched control tasks. Chronometric TMS was delivered over the left ATL (10 mm from the tip of the temporal pole along the middle temporal gyrus). During each trial, two pulses of TMS (40 msec apart) were delivered either at baseline (before stimulus presentation) or at one of the experimental time points 100, 250, 400, and 800 msec poststimulus onset. A significant disruption to performance was identified from 400 msec on the semantic task but not on the control assessment. Our results not only reinforce the key role of the left ATL in semantic representation but also indicate that its contribution is especially important around 400 msec poststimulus onset. Together, these facts suggest that the ATL may be one of the neural sources of the N400 ERP component.

Is the response to rTMS largely the result of non-specific effects?

2021 ◽  
Vol 55 (5) ◽  
pp. 445-450
Author(s):  
Gin S Malhi ◽  
Erica Bell
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Clinical Response ◽  
Magnetic Stimulation ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Clinical Profile ◽  
Placebo Effects ◽  
Specific Effects ◽  
Treatment Of Depression

The efficacy of repetitive transcranial magnetic stimulation (rTMS) in the treatment of depression is disputed. This is partly because, to date, insufficient good-quality studies have been conducted, and a definitive clinical profile for which rTMS is best suited is yet to be determined. However, another equally important reason for questioning the efficacy of rTMS is that the clinical response to its application is thought to be the result of predominantly non-specific and placebo effects. Therefore, in this viewpoint we examine this possibility in detail and propose a meaningful way forward for rTMS research.

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