A systematic review of the neurobiological effects of theta-burst stimulation (TBS) as measured using functional magnetic resonance imaging (fMRI)

Abstract

Theta burst stimulation (TBS) is associated with the modulation of a range of clinical, cognitive, and behavioural outcomes, but specific neurobiological effects remain somewhat unclear. This systematic literature review investigated resting-state and task-based functional magnetic resonance imaging (fMRI) outcomes post-TBS in healthy human adults. Fifty studies that applied either continuous—or intermittent—(c/i) TBS, and adopted a pretest–posttest or sham-controlled design, were included. For resting-state outcomes following stimulation applied to motor, temporal, parietal, occipital, or cerebellar regions, functional connectivity generally decreased in response to cTBS and increased in response to iTBS, though there were some exceptions to this pattern of response. These findings are mostly consistent with the assumed long-term depression (LTD)/long-term potentiation (LTP)-like plasticity effects of cTBS and iTBS, respectively. Task-related outcomes following TBS were more variable. TBS applied to the prefrontal cortex, irrespective of task or state, also produced more variable responses, with no consistent patterns emerging. Individual participant and methodological factors are likely to contribute to the variability in responses to TBS. Future studies assessing the effects of TBS via fMRI must account for factors known to affect the TBS outcomes, both at the level of individual participants and of research methodology.

Theta-burst direct electrical stimulation remodels human brain networks

“…This type of state-dependent accumulated brain changes that may result from spaced and repeated stimulation is referred to as metaplasticity and is well-known in non-human models 102–104 . Indeed, intermittent TBS – delivering repeated and spaced TBS trains (as in this study) –has been shown to produce neural changes that could reflect plasticity while continuous TBS (no spacing between trains) did not – an effect which could be NMDA-receptor dependent 14,68,109 . In other words, intermittent TBS could be more conducive to triggering plastic changes in the human brain.…”

Neuroimaging and serum biomarkers of neurodegeneration and neuroplasticity in Parkinson’s disease patients treated by intermittent theta-burst stimulation over the bilateral primary motor area: a randomized, double-blind, sham-controlled, crossover trial study

“…It is more probable that many of the positive effects of TBS are the result of the secondary activation of glial cells, although there is limited information regarding the response of glial cells to these neuromodulation techniques ( Cullen and Young, 2016 ), particularly in relation to iTBS-induced plasticity effects ( Cacace et al, 2017 ). Moreover, knowledge about how intracortical structures, cortico-subcortical functional connectivity, and brain volume changes are involved in the modulatory effects of rTMS and TBS is still limited ( Di Lazzaro and Rothwell, 2014 ; Peters et al, 2020 ; Jannati et al, 2023 ; Kirkovski et al, 2023 ).…”

Transcranial burst electrical stimulation contributes to neuromodulatory effects in the rat motor cortex

“…For example, anodal tDCS increases neuronal excitability, producing long-term potentiation (LTP)-like effects, while cathodal tDCS induces long-term depression (LTD)-like effects ( Rroji et al, 2015 ; Kronberg et al, 2017 ). Additionally, continuous TBS (cTBS) induces LTD-like cortical plasticity, whereas intermittent TBS (iTBS) produces LTP-like effects ( Kirkovski et al, 2023 ). In this study, the tBES pattern combines both facilitation and inhibition waveforms from direct current and TBS.…”