The effects of individualised intermittent theta burst stimulation in the prefrontal cortex: A TMS‐EEG study

Abstract

Recent studies have highlighted variability in response to theta burst stimulation (TBS) in humans. TBS paradigm was originally developed in rodents to mimic gamma bursts coupled with theta rhythms, and was shown to elicit long‐term potentiation. The protocol was subsequently adapted for humans using standardised frequencies of stimulation. However, each individual has different rhythmic firing pattern. The present study sought to explore whether individualised intermittent TBS (Ind iTBS) could outperform the effects of two other iTBS variants. Twenty healthy volunteers received iTBS over left prefrontal cortex using 30 Hz at 6 Hz, 50 Hz at 5 Hz, or individualised frequency in separate sessions. Ind iTBS was determined using theta‐gamma coupling during the 3‐back task. Concurrent use of transcranial magnetic stimulation and electroencephalography (TMS‐EEG) was used to track changes in cortical plasticity. We also utilised mood ratings using a visual analogue scale and assessed working memory via the 3‐back task before and after stimulation. No group‐level effect was observed following either 30 or 50 Hz iTBS in TMS‐EEG. Ind iTBS significantly increased the amplitude of the TMS‐evoked P60, and decreased N100 and P200 amplitudes. A significant positive correlation between neurophysiological change and change in mood rating was also observed. Improved accuracy in the 3‐back task was observed following both 50 Hz and Ind iTBS conditions. These findings highlight the critical importance of frequency in the parameter space of iTBS. Tailored stimulation parameters appear more efficacious than standard paradigms in neurophysiological and mood changes. This novel approach presents a promising option and benefits may extend to clinical applications.

Combining HF rTMS over the Left DLPFC with Concurrent Cognitive Activity for the Offline Modulation of Working Memory in Healthy Volunteers: A Proof-of-Concept Study

“…Consistent with our results, significant effects of HF rTMS protocols without a cognitive load on WM performance have been obtained in several studies. Different TMS protocols were used, including HF [46] and LF rTMS [19], as well as cTBS [21,47] and iTBS [20,48]. Improvement of WM accuracy and reaction times after HF rTMS over DLPFC was also confirmed in a meta-analysis; however, the inhomogeneity of the analyzed studies remains an important limitation [25].…”

Stanford Accelerated Intelligent Neuromodulation Therapy for Treatment-Resistant Depression (SAINT-TRD)

“…It is possible that different stimulation sites may be optimal for certain patients based on their symptom profile [74][75][76] . The use of individualized stimulation frequencies may result in quicker and more durable responses 77,80 . Some individuals may require slightly different inter-session intervals due to differences in cortical excitability profiles 78,81 .…”

Sheaves in the Brain Elucidate the Behavior of Entrained Oscillations<strong> </strong>

“…(Benali et al, 2011). At present, there is no systematic method to predict which neural elements will be activated by a given stimulation regime (Komarov et al, 2019), because each individual has different rhythmic firing pattern in response to burst stimulation (Chung et al, 2019) and spike initiation site may change for short and long pulses (Rattay et al, 2012). Our model sheds new light on the mechanisms of rTMS, suggesting that axonal stimulations from external sources might modify the frequency charges of the involved neurons.…”