Computation and Neural Systems, California Institute of Technology, Pasadena, CA, 91125.
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125.
eNeuro. 2019 Apr 26;6(2). doi: 10.1523/ENEURO.0483-18.2019. Print 2019 Mar/Apr.
Magnetoreception, the perception of the geomagnetic field, is a sensory modality well-established across all major groups of vertebrates and some invertebrates, but its presence in humans has been tested rarely, yielding inconclusive results. We report here a strong, specific human brain response to ecologically-relevant rotations of Earth-strength magnetic fields. Following geomagnetic stimulation, a drop in amplitude of electroencephalography (EEG) alpha-oscillations (8-13 Hz) occurred in a repeatable manner. Termed alpha-event-related desynchronization (alpha-ERD), such a response has been associated previously with sensory and cognitive processing of external stimuli including vision, auditory and somatosensory cues. Alpha-ERD in response to the geomagnetic field was triggered only by horizontal rotations when the static vertical magnetic field was directed downwards, as it is in the Northern Hemisphere; no brain responses were elicited by the same horizontal rotations when the static vertical component was directed upwards. This implicates a biological response tuned to the ecology of the local human population, rather than a generic physical effect. Biophysical tests showed that the neural response was sensitive to static components of the magnetic field. This rules out all forms of electrical induction (including artifacts from the electrodes) which are determined solely on dynamic components of the field. The neural response was also sensitive to the polarity of the magnetic field. This rules out free-radical "quantum compass" mechanisms like the cryptochrome hypothesis, which can detect only axial alignment. Ferromagnetism remains a viable biophysical mechanism for sensory transduction and provides a basis to start the behavioral exploration of human magnetoreception.
磁感觉，即对地球磁场的感知，是一种在所有主要的脊椎动物和一些无脊椎动物中都已确立的感觉方式，但在人类中对其进行的测试很少，结果也不一致。我们在此报告了一种强烈的、特定的人类大脑对生态相关的地球强度磁场旋转的反应。在地球磁场刺激后，脑电图（EEG）α 振荡（8-13Hz）的振幅以可重复的方式下降。这种反应被称为α-事件相关去同步化（alpha-ERD），之前曾与外部刺激的感觉和认知处理有关，包括视觉、听觉和体感提示。只有当垂直静磁场向下指向，如在北半球，而水平静磁场向上指向时，水平旋转才会引发与磁场相关的α-ERD，不会引起相同的水平旋转产生大脑反应。这表明存在一种针对当地人类群体生态的生物反应，而不是一种普遍的物理效应。生物物理测试表明，神经反应对磁场的静态分量敏感。这排除了所有形式的磁感应（包括来自电极的伪影），这些感应仅取决于磁场的动态分量。神经反应也对磁场的极性敏感。这排除了像隐花色素假说那样的自由基“量子罗盘”机制，因为后者只能检测轴向对齐。顺磁性仍然是一种可行的感觉转导生物物理机制，并为开始探索人类磁感觉的行为提供了基础。
