Neural Noise- Concurrent TBS and fNIRS can be used to explore the predictive power of iTBS-induced prefrontal excitability.1
- The approach informs stimulation dosing and non-invasive biomarkers for neuromodulation.1 1
Weekly enrichment (2026-07-20)
- The source study, “Exploring the predictive power of iTBS-induced prefrontal excitability using concurrent TBS/fNIRS,” was published in Nature Scientific Reports (received 30 May 2025).2
- It used a randomized, double-blind, sham-controlled, repeated-measures crossover design with 30 healthy, right-handed, TMS-naive participants (ages 18-60, college students averaging over 17 years of education); each attended two sessions at least 7 days apart.2
- iTBS was delivered over the left DLPFC (MNI coordinates x = -38, y = +44, z = +26) at 80% of individual resting motor threshold using a 70-mm figure-eight Cool-B65 coil and a MagPro X100 stimulator, following the standard Huang protocol of 600 pulses (20 trains of ten 3-pulse 50 Hz bursts at 5 Hz, 8-s inter-train rest).2
- Working memory was measured with a 3-back task at six timepoints (pre; 0, 10, 20, 30, 40 min post-iTBS), while prefrontal HbO and HbR were tracked concurrently with a frequency-domain fNIRS system (ISS OxiTs, 8 emitters over left DLPFC).2
- Behavioral data from all 30 participants per condition were analyzed, but 5 active and 5 sham fNIRS datasets were excluded for low signal quality, leaving 25 per condition (50 hemoglobin datasets) for the hemodynamic analysis.2
- Active iTBS produced a significant iTBS-induced HbO decrease versus sham (p = 0.006) and a within-active decrease during iTBS relative to baseline (p < 0.001, corrected), confirming a stimulation-specific excitability change.2
- There was no significant group difference in post-stimulation 3-back performance; d-prime, reaction times and ΔHbO all improved over time in both groups (significant main effect of time, e.g. d-prime F = 2.683, p = 0.021), attributed to practice effects rather than iTBS.2
- Simple linear regressions (significance threshold p < 0.001 after correction) found that iTBS-induced HbO change did NOT predict working memory at any timepoint, so single-session prefrontal excitability was not a predictor of memory gains.2
- The authors argue the predictive value of iTBS-induced excitability for rTMS antidepressant response is still worth testing as an imaging biomarker in larger samples; a related registered protocol (ClinicalTrials.gov NCT06104462) uses concurrent TBS/fNIRS to probe inter- and intra-individual moderators of iTBS excitability variability.23