重复经颅磁刺激对视觉诱发电位的影响:健康受试者的新见解
Effects of repetitive transcranial magnetic stimulation on visual evoked potentials: new insights in healthy subjects.
作者信息
Fumal Arnaud, Bohotin Valentin, Vandenheede Michel, Seidel Laurence, de Pasqua Victor, de Noordhout Alain Maertens, Schoenen Jean
机构信息
University Department of Neurology, CHR Citadelle Hospital, 4000 Liège, Belgium.
出版信息
Exp Brain Res. 2003 Jun;150(3):332-40. doi: 10.1007/s00221-003-1423-7. Epub 2003 Apr 16.
In a previous comparative study with migraineurs, we found in 24 normal subjects that the amplitude of the pattern-reversal visual evoked potential (PR-VEP) in the first block of 100 responses and its habituation over 6 sequential blocks were significantly decreased after 1 Hz repetitive transcranial magnetic stimulation (rTMS), while 10 Hz rTMS had no significant effect. We report here our results on the reproducibility of the rTMS effect studied in ten of these subjects by repeating the recordings for each frequency three times on different days. We have also reanalysed the data obtained in 24 normal subjects, looking separately at the results in those stimulated at an intensity equal to phosphene threshold (group 1; n=14) and those stimulated at 110% of motor threshold because of unelicitable phosphenes (group 2; n=10). We finally determined the precise duration of the rTMS effect. Despite some interindividual variability, the effects of both rTMS frequencies on first block amplitude, habituation between first and sixth block and habituation slope over the six blocks were highly reproducible. The only difference between the two groups of subjects was the effect of 1 Hz rTMS on the second measured PR-VEP component. Whereas first block amplitude of the first P1-N1 component and habituation were decreased in both groups, such a decrease was found for the second P1-N2 component only in group 1 stimulated at phosphene threshold. The dishabituation of the N1-P1 component after 1 Hz rTMS was maximal at 15 min, but lasted up to 33 min, while that of P1-N2 disappeared after 3 min. There was a non-significant trend ( p=0.06) for a reduction of first block amplitude after 10 Hz rTMS in the total group of subjects, but no effect on habituation. The inhibitory effect of 1 Hz rTMS, which reduces in healthy controls both first block PR-VEP amplitude and habituation, probably by decreasing the preactivation excitability level of the underlying visual cortex, is thus reproducible and long lasting. Long trains of 10 Hz rTMS tend to attenuate reproducibly the cortical preactivation level in normal subjects, but they do not affect habituation at all, which contrasts with their effect in migraineurs, in whom, as previously reported, they significantly correct the habituation deficit. The absence of an effect of 1 Hz rTMS on PR-VEP P1-N2 in subjects stimulated at 110% of motor threshold may be explained by the deeper anatomical location of the cortical generators of this component and the lower stimulation intensity used. Taken together our results confirm that the effect of rTMS on the underlying cortex depends on several variables such as frequency, intensity and level of cortical preactivation.
在之前一项针对偏头痛患者的对比研究中,我们发现,在24名正常受试者中,1赫兹重复经颅磁刺激(rTMS)后,100次反应的第一个时间段内图形翻转视觉诱发电位(PR-VEP)的波幅及其在6个连续时间段内的习惯化现象显著降低,而10赫兹rTMS则无显著影响。在此,我们报告对其中10名受试者重复进行不同频率记录三次(在不同日期)所研究的rTMS效应的可重复性结果。我们还重新分析了在24名正常受试者中获得的数据,分别查看了以等于光幻视阈值的强度进行刺激的受试者(第1组;n = 14)以及因无法引出光幻视而以运动阈值的110%强度进行刺激的受试者(第2组;n = 10)的结果。我们最终确定了rTMS效应的精确持续时间。尽管存在个体差异,但两种rTMS频率对第一个时间段波幅、第一个和第六个时间段之间的习惯化以及六个时间段内的习惯化斜率的影响具有高度可重复性。两组受试者之间的唯一差异在于1赫兹rTMS对第二次测量的PR-VEP成分的影响。虽然两组中第一个P1-N1成分的第一个时间段波幅和习惯化均降低,但仅在以光幻视阈值进行刺激的第1组中,第二个P1-N2成分出现了这种降低。1赫兹rTMS后N1-P1成分的去习惯化在15分钟时最大,但持续长达33分钟,而P1-N2成分的去习惯化在3分钟后消失。在所有受试者中,10赫兹rTMS后第一个时间段波幅有降低的趋势但不显著(p = 0.06),对习惯化无影响。1赫兹rTMS的抑制作用可能是通过降低潜在视觉皮层的预激活兴奋性水平,从而降低了健康对照组中第一个时间段PR-VEP波幅和习惯化,这种作用是可重复且持久的。长时间的10赫兹rTMS倾向于可重复地降低正常受试者的皮层预激活水平,但对习惯化完全没有影响,这与它们在偏头痛患者中的作用形成对比,如先前报道,它们在偏头痛患者中能显著纠正习惯化缺陷。在以运动阈值的110%强度进行刺激的受试者中,1赫兹rTMS对PR-VEP P1-N2无影响,这可能是由于该成分的皮层发生器解剖位置更深以及所用刺激强度较低所致。综合我们的结果证实,rTMS对潜在皮层的影响取决于几个变量,如频率、强度和皮层预激活水平。