Valero-Cabré Antoni, Pascual-Leone Alvaro, Rushmore Richard J
Laboratory for Cerebral Dynamics, Plasticity and Rehabilitation, Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
Eur J Neurosci. 2008 Feb;27(3):765-74. doi: 10.1111/j.1460-9568.2008.06045.x.
A single session of repetitive transcranial magnetic stimulation (rTMS) can induce behavioural effects that outlast the duration of the stimulation train itself (off-line effects). Series of rTMS sessions on consecutive days are being used for therapeutic applications in a variety of disorders and are assumed to lead to the build-up of cumulative effects. However, no studies have carefully assessed this notion. In the present study we applied 30 daily sessions of 1 Hz rTMS (continuous train of 20 min) to repeatedly modulate activity in the posterior parietal cortex and associated neural systems in two intact cats. We assessed the effect on visuospatial orientation before and after each stimulation session. Cumulative sessions of rTMS progressively induced visuospatial neglect-like 'after-effects' of greater magnitude (from 5-10% to 40-50% error levels) and increasing spatial extent (from 90-75 degrees to 45-30 degrees eccentricity locations), affecting the visual hemifield contralateral to the stimulated hemisphere. Nonetheless, 60 min after each TMS session, visual detection-localization abilities repeatedly returned to baseline levels. Furthermore, no lasting behavioural effect could be demonstrated at any time across the study, when subjects were tested 1 or 24 h post-rTMS. We conclude that the past history of periodically cumulative rTMS sessions builds up a lasting 'memory', resulting in increased facilitation to subsequent TMS-induced disruptions. Such a phenomenon allows a behavioural effect of progressively higher magnitude, but equal duration, in response to individual TMS interventions.
单次重复经颅磁刺激（rTMS）可诱发行为效应，且这种效应持续时间超过刺激序列本身（离线效应）。连续数天进行一系列rTMS治疗已被用于多种疾病的治疗，并被认为会产生累积效应。然而，尚无研究仔细评估这一概念。在本研究中，我们对两只完整的猫的后顶叶皮质及相关神经系统进行了30天的每日1Hz rTMS治疗（20分钟连续刺激序列），以反复调节其活动。我们在每次刺激前后评估了对视觉空间定向的影响。累积的rTMS治疗逐渐诱发了类似视觉空间忽视的“后效应”，其程度更大（从5%-10%的误差水平增至40%-50%），空间范围也不断扩大（从90°-75°的偏心率位置增至45°-30°），影响受刺激半球对侧的视觉半视野。尽管如此，每次TMS治疗后60分钟，视觉检测-定位能力会反复恢复到基线水平。此外，在rTMS后1小时或24小时对受试者进行测试时，在整个研究过程中的任何时间都未发现持久的行为效应。我们得出结论，过去周期性累积的rTMS治疗会形成持久的“记忆”，导致对后续TMS诱发的干扰的易化作用增强。这种现象使得针对个体TMS干预能够产生幅度逐渐增大但持续时间相同的行为效应。
