BACKGROUND Evidence suggests that repetitive transcranial magnetic stimulation (rTMS), a non-invasive neuromodulation technique, alters resting brain activity. Despite anecdotal evidence that rTMS effects wear off, there are no reports of longitudinal studies, even in humans, mapping the therapeutic duration of rTMS effects. OBJECTIVE Here, we investigated the longitudinal effects of repeated low-intensity rTMS (LI-rTMS) on healthy rodent resting-state networks (RSNs) using resting-state functional MRI (rs-fMRI) and on sensorimotor cortical neurometabolite levels using proton magnetic resonance spectroscopy (MRS). METHODS Sprague-Dawley rats received 10 min LI-rTMS daily for 15 days (10 Hz or 1 Hz stimulation, n = 9 per group). MRI data were acquired at baseline, after seven days and after 14 days of daily stimulation and at two more timepoints up to three weeks post-cessation of daily stimulation. RESULTS 10 Hz stimulation increased RSN connectivity and GABA, glutamine, and glutamate levels. 1 Hz stimulation had opposite but subtler effects, resulting in decreased RSN connectivity and glutamine levels. The induced changes decreased to baseline levels within seven days following stimulation cessation in the 10 Hz group but were sustained for at least 14 days in the 1 Hz group. CONCLUSION Overall, our study provides evidence of long-term frequency-specific effects of LI-rTMS. Additionally, the transient connectivity changes following 10 Hz stimulation suggest that current treatment protocols involving this frequency may require ongoing "top-up" stimulation sessions to maintain therapeutic effects.

中文翻译：

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低强度 rTMS 的频率特异性效应可以在刺激后持续长达 2 周：大鼠的纵向 rs-fMRI/MRS 研究

背景 证​​据表明，重复经颅磁刺激 (rTMS)，一种非侵入性神经调节技术，会改变静息大脑活动。尽管有轶事证据表明 rTMS 效应会消失，但没有纵向研究报告，即使在人类中，也没有绘制 rTMS 效应的治疗持续时间。目的 在这里，我们研究了重复低强度 rTMS (LI-rTMS) 对健康啮齿动物静息状态网络 (RSNs) 使用静息状态功能 MRI (rs-fMRI) 和使用质子磁共振对感觉运动皮层神经代谢物水平的纵向影响光谱（MRS）。方法 Sprague-Dawley 大鼠每天接受 10 分钟 LI-rTMS，持续 15 天（10 Hz 或 1 Hz 刺激，每组 n = 9）。MRI 数据是在基线时获得的，在每天刺激 7 天后和 14 天后，以及在每天刺激停止后长达三周的另外两个时间点。结果 10 Hz 刺激增加了 RSN 连接和 GABA、谷氨酰胺和谷氨酸水平。1 Hz 刺激具有相反但更微妙的效果，导致 RSN 连接性和谷氨酰胺水平降低。在 10 Hz 组中刺激停止后 7 天内，诱导的变化降至基线水平，但在 1 Hz 组中持续至少 14 天。结论 总的来说，我们的研究提供了 LI-rTMS 的长期频率特异性影响的证据。此外，10 Hz 刺激后的瞬态连接变化表明当前涉及该频率的治疗方案可能需要持续的“补充”刺激会话以维持治疗效果。