Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, United States; Department of Neurosciences, Medical University of South Carolina, Charleston, SC, United States.
Department of Radiology, Medical University of South Carolina, Charleston, SC, United States; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, United States.
Brain Stimul. 2018 Jul-Aug;11(4):789-796. doi: 10.1016/j.brs.2018.02.014. Epub 2018 Feb 24.
In the 20 years since our group established the feasibility of performing interleaved TMS/fMRI, no studies have reported direct comparisons of active prefrontal stimulation with a matched sham. Thus, for all studies there is concern about what is truly the TMS effect on cortical neurons.
After developing a sham control for use within the MRI scanner, we used fMRI to test the hypothesis of greater regional BOLD responses for active versus control stimulation.
We delivered 4 runs of interleaved TMS/fMRI with a limited field of view (16 slices, centered at AC-PC) to the left DLPFC (2 active, 2 control; counterbalanced) of 20 healthy individuals (F3; 20 pulses/run, interpulse interval:10-15sec, TR:1sec). In the control condition, 3 cm of foam was placed between the TMS coil and the scalp. This ensured magnetic field decay, but preserved the sensory aspects of each pulse (empirically evaluated in a subset of 10 individuals).
BOLD increases in the cingulate, thalamus, insulae, and middle frontal gyri (p < 0.05, FWE corrected) were found during both active and control stimulation. However, relative to control, active stimulation caused elevated BOLD signal in the anterior cingulate, caudate and thalamus. No significant difference was found in auditory regions.
CONCLUSION(S): This TMS/fMRI study evaluated a control condition that preserved many of the sensory features of TMS while reducing magnetic field entry. These findings support a relationship between single pulses of TMS and activity in anatomically connected regions, but also underscore the importance of using a sham condition in future TMS/fMRI studies.
自我们小组证实了在磁共振成像仪中进行交错经颅磁刺激和功能磁共振成像的可行性以来，已有 20 年，目前还没有研究报告直接比较过主动前额叶刺激与匹配的假刺激。因此，所有研究都关注的是真正的经颅磁刺激对皮质神经元的影响。
在开发出一种可在磁共振成像仪内使用的假刺激对照后，我们使用功能磁共振成像来检验一个假设，即主动刺激相较于对照刺激会引起更大的局部血氧水平依赖信号反应。
我们对 20 名健康个体的左侧背外侧前额叶皮层（F3；20 个脉冲/轮，脉冲间隔 10-15 秒，重复时间 1 秒）进行了 4 轮交错经颅磁刺激和功能磁共振成像。在对照条件下，在经颅磁刺激线圈和头皮之间放置 3 厘米厚的泡沫，这确保了磁场衰减，但保留了每个脉冲的感觉方面（在 10 名个体的子集中进行了实证评估）。
在主动和对照刺激期间，都发现了扣带回、丘脑、脑岛和中额回的大脑血氧水平依赖信号增加（p<0.05，经校正的全脑错误发现率校正）。然而，与对照相比，主动刺激引起了前扣带回、尾状核和丘脑的大脑血氧水平依赖信号升高。在听觉区域没有发现显著差异。
这项经颅磁刺激和功能磁共振成像研究评估了一种对照条件，这种条件保留了经颅磁刺激的许多感觉特征，同时减少了磁场进入。这些发现支持了单个经颅磁刺激脉冲与解剖上连接区域的活动之间的关系，但也强调了在未来的经颅磁刺激和功能磁共振成像研究中使用假刺激对照的重要性。
