Frontal electroencephalographic (EEG) activity and mediumship: a comparative study between spiritist mediums and controls

Abstract Mediumship and spirit possession are cultural phenomena found worldwide. The Spiritism, popular in Brazil, is a religious tradition that emphasizes mediumship. The “absorption hypothesis” (the association of marked increases in focused attention with concomitant decreases in self-awareness) is one of the neuropsychological explanatory theories for these experiences. We measured electroencephalographic (EEG) spectral power in frontal electrodes within theta, alpha and beta bandwidths, as well as cross-regional cortical coherences, in female Spiritist experienced mediums (n = 10) and in female non-medium control subjects from the same religious context (n = 10). Scalp EEG signals were captured simultaneously from participants in each of the two groups in three different moments: before, during and immediately after mediumistically speaking. Compared to non-medium controls, the mediums had greater beta power on some electrodes in all phases of the experiment, greater theta power on one electrode at the communication phase and greater alpha power on one electrode at the post-communication phase. No condition effects (within-group comparisons) were detected in any group. No group effects were noted for cross regional cortical coherences. No ictal EEG pattern was observed, except for one participant in the mediums group. These findings support the hypothesis that absorption could have a mechanistic role in anomalous sensorial experiences such as mediumship. The coherence pattern in mediums during the anomalous experience differed from prior studies on pathological dissociation and on hypnotic states. Cognitive control processes seem to be engaged during the anomalous sensorial experiences.

摘要：通灵现象与灵体附身是遍布全球的文化现象。在巴西广为流传的唯灵论（Spiritism）是一门强调通灵的宗教传统。“沉浸假说（absorption hypothesis）”——即高度集中注意力伴随自我意识显著降低的关联现象——是解释这类体验的神经心理学理论之一。
本研究针对10名有通灵经验的女性唯灵论者，以及10名来自同一宗教背景的女性非通灵对照受试者，测量了其额叶电极在θ、α、β频段的脑电图（electroencephalographic, EEG）频谱功率，以及跨区域皮层相干性。
研究同步采集了两组受试者在三个不同时段的头皮脑电信号，三个时段分别为通灵发言前、通灵发言期间及通灵发言结束后即刻。
与非通灵对照组相比，通灵组在实验全部阶段的部分电极上β频段功率更高，在交流阶段的单一侧电极上θ频段功率更高，且在交流后阶段的单一侧电极上α频段功率更高。
两组内部的各时段比较均未检测到显著条件效应。跨区域皮层相干性未观察到显著组间差异。除通灵组1名受试者外，未观察到发作性脑电模式。
上述研究结果支持“沉浸假说在通灵这类异常感官体验中可能发挥机制性作用”的论断。
通灵者在异常体验期间的皮层相干模式，与此前针对病理性解离及催眠状态的相关研究结果存在差异。
认知控制过程似乎在异常感官体验期间被激活。