The immediate impact of transcranial magnetic stimulation on brain structure: Short-term neuroplasticity following one session of cTBS

Jeyoung Jung,Matthew A Lambon Ralph

doi:10.1016/j.neuroimage.2021.118375

Abstract

Recent evidence demonstrates that activation-dependent neuroplasticity on a structural level can occur in a short time (2 hour or less) in the human brain. However, the exact time scale of structural plasticity in the human brain remains unclear. Using voxel-based morphometry (VBM), we investigated changes in grey matter (GM) after one session of continuous theta-burst stimulation (cTBS) delivered to the anterior temporal lobe (ATL). Twenty-five participants received cTBS over the left ATL or the occipital pole as a control site outside of the scanner, followed by structural and functional imaging. During functional imaging, participants performed a semantic association task and a number judgment task as a control task. VBM results revealed decreased GM in the left ATL and right cerebellum after the ATL stimulation compared to the control stimulation. In addition, cTBS over the left ATL induced slower semantic reaction times, reduced regional activity at the target site, and altered functional connectivity between the left and right ATL during semantic processing. Furthermore, the decreased ATL GM density was associated with the interhemispheric ATL-connectivity changes after the ATL stimulation. These results demonstrate that structural alterations caused by one session of cTBS are mirrored in the functional reorganizations in the semantic representation system, showing the rapid dynamics of cortical plasticity. Our findings support fast adapting neuronal plasticity such as synaptic morphology changes. Our results suggest that TBS is able to produce powerful changes in regional synaptic activity in the adult human brain.

Highlights

Neuroplasticity refers to the brain’s ability to reorganize itself in response to environmental changes and involves a complex, multilayer process including the molecular, synaptic, electrophysiological and structural organization level
We here summarized the key findings from the previous study and reported findings related to changes in gray matter (GM) and white matter (WM) induced by continuous theta-burst stimulation (cTBS)
Our results suggest that structural alterations in GM can occur very rapidly with one session of cTBS

Summary

Introduction

Neuroplasticity refers to the brain’s ability to reorganize itself in response to environmental changes and involves a complex, multilayer process including the molecular, synaptic, electrophysiological and structural organization level. The scope of neuroplasticity encompasses functional forms including short-term weakening and strengthening of existing synapses through long-term potentiation (LTP) and longterm depression (LTD) and structural types such as synaptogenesis, gliogenesis, and neurogenesis (Bruel-Jungerman et al, 2007; Butz et al, 2009; Holtmaat and Svoboda, 2009). Participants in the learning group performed a spatial learning and memory task for 90min on average and microstructural changes of hippocampus and parahippocampus were observed with improved task performance in the learning group compared to the control group (no learning) Their findings were replicated in a subsequent rat study such that there was structural remodelling of the rat hippocampus following 2 hour of water maze task (Sagi et al, 2012). It is important to understand what extent the structural plasticity arises in adult’s brain following environment demands and disease because this type of cortical plasticity is associated with short-and long-term therapeutic effects

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