Transcranial magnetic stimulation of the left angular gyrus during encoding does not impair associative memory performance

Phonologically similar items (mell, rell, gell) are more difficult to remember than dissimilar items (shen, floy, stap), likely because of mutual interference of the items in the phonological store. Low-frequency transcranial magnetic stimulation (TMS), guided by functional magnetic resonance imaging (fMRI) was used to disrupt this phonological confusion by stimulation of the left inferior parietal (LIP) lobule. Subjects received TMS or placebo stimulation while remembering sets of phonologically similar or dissimilar pseudo-words. Consistent with behavioral performance of patients with neurological damage, memory for phonologically similar, but not dissimilar, items was enhanced following TMS relative to placebo stimulation. Stimulation of a control region of the brain did not produce any changes in memory performance. These results provide new insights into how the brain processes verbal information by establishing the necessity of the inferior parietal region for optimal phonological storage. A mechanism is proposed for how TMS reduces phonological confusion and leads to facilitation of phonological memory.

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Cognitive Improvement Via Left Angular Gyrus-Navigated Repetitive Transcranial Magnetic Stimulation Inducing the Neuroplasticity of Thalamic System in Alzheimer’s Disease Spectrum Patients

10.21203/rs.3.rs-812265/v1 ◽

2021 ◽

Author(s):

Zhiyuan Yang ◽

Xiaoning Sheng ◽

Ruomeng Qin ◽

Haifeng Chen ◽

Pengfei Shao ◽

...

Keyword(s):

Cognitive Impairment ◽

Transcranial Magnetic Stimulation ◽

Magnetic Stimulation ◽

Diffusion Tensor ◽

Repetitive Transcranial Magnetic Stimulation ◽

Disease Process ◽

Functional Network ◽

Angular Gyrus ◽

Cognitive Improvement ◽

Left Angular Gyrus

Abstract Background: Stimulating superficial brain regions highly associated with the hippocampus by repetitive transcranial magnetic stimulation (rTMS) may improve memory of Alzheimer disease (AD) spectrum patients. Methods: We recruited 26 mild cognitive impairment (MCI) and AD patients. All the patients were stimulated to the left angular gyrus, which was confirmed a strong link to the hippocampus through neuroimaging studies, by the neuro-navigated rTMS for four weeks. Automated fiber quantification (AFQ) using diffusion tensor imaging (DTI) metrics and graph theory analysis on functional network were employed to detect the neuroplasticity of brain networks. Results: After neuro-navigated rTMS intervention, the episodic memory and language function of patients were significantly improved. Increased white matter integrity of right anterior thalamic radiation among MCI patients, while decreased functional network properties of thalamus subregions were observed. It is worth noting that the improvement of cognition was associated with the neuroplasticity of thalamic systemConclusions: We speculated that the rTMS intervention targeting left angular gyrus may be served as a strategy to improve cognitive impairment in AD spectrum patients, supporting by the neuroplasticity of thalamic system, especially in the early disease process at the stage of MCI.

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Interhemispheric interactions between the right angular gyrus and the left motor cortex: a transcranial magnetic stimulation study

Journal of Neurophysiology ◽

10.1152/jn.00642.2020 ◽

2021 ◽

Author(s):

Julianne Baarbé ◽

Michael Vesia ◽

Matt Brown ◽

Karlo J. Lizarraga ◽

Carolyn A Gunraj ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Posterior Parietal Cortex ◽

Short Interval ◽

Intracortical Inhibition ◽

Angular Gyrus ◽

Posterior Parietal ◽

The Right ◽

Left Angular Gyrus

The interconnection of the angular gyrus of right posterior parietal cortex (PPC) and the left motor cortex (LM1) is essential for goal-directed hand movements. Previous work with transcranial magnetic stimulation (TMS) showed that right PPC stimulation increases LM1 excitability but right PPC followed by left PPC-LM1 stimulation (LPPC-LM1) inhibits LM1 corticospinal output compared to LPPC-LM1 alone. It is not clear if right PPC-mediated inhibition of LPPC-LM1 is due to inhibition of left PPC or to combined effects of right and left PPC stimulation on LM1 excitability. We used paired-pulse TMS to study the extent to which combined right and left PPC stimulation, targeting the angular gyri, influences LM1 excitability. We tested 16 healthy subjects in five paired-pulsed TMS experiments using MRI-guided neuronavigation to target the angular gyri within PPC. We tested the effects of different right angular gyrus (RAG) and LM1 stimulation intensities on the influence of RAG on LM1 and on influence of left angular gyrus (LAG) on LM1 (LAG-LM1). We then tested the effects of RAG and LAG stimulation on LM1 short-interval intracortical facilitation(SICF), short-interval intracortical inhibition(SICI) and long-interval intracortical inhibition(LICI). The results revealed that RAG facilitated LM1, inhibited SICF and inhibited LAG-LM1. Combined RAG-LAG stimulation did not affect SICI but increased LICI. These experiments suggest that RAG-mediated inhibition of LAG-LM1 is related to inhibition of early I-wave activity and enhancement of GABAB receptor-mediated inhibition in LM1. The influence of RAG on LM1 likely involves ipsilateral connections from LAG to LM1 and heterotopic connections from RAG to LM1.

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