约翰·霍普金斯医学院的研究推翻了对神经元基本结构的长期认知。1研究团队发现，脑细胞轴突的实际形态并非教科书中描绘的光滑管状结构，而是呈现出珍珠串状的微小隆起。1这些被称为非突触空泡体的结构宽度仅为人类头发的约百分之一，研究使用高压冷冻电子显微镜保留了细胞的原始形状以观察这一微观特征。1
研究表明，这种珍珠状结构并非静止不变，而是受膜物理学控制并随神经活动动态变化。1当施加高频电刺激后，珍珠状区域的平均长度增加了8%，宽度增加了17%，这种变化至少持续30分钟。1同时，电信号在轴突中的传导速度随之减慢，效果至少维持1小时。1研究人员通过移除膜上的胆固醇使膜变得更液态，结果改变了珍珠结构并进一步降低了电信号速度，这进一步确认了膜物理性质对轴突形态的影响。1
这项发现已在人脑组织中得到验证。1研究人员在癫痫手术获取的人脑皮层组织中观察到了相同的珍珠状轴突结构。1相关研究发表于2024年12月2日在线版《自然神经科学》，后续验证研究发表于2025年11月的《神经元》期刊。1
Researchers at Johns Hopkins School of Medicine have discovered that the axons of brain cells do not possess the smooth, tube-like structure long depicted in textbooks, but instead feature a beaded or pearl-string appearance with tiny repeated bulges.1 These non-synaptic varicosities—microscopic enlargements along the axon—are governed by membrane physics and can change shape in response to neural activity, thereby altering the speed at which electrical signals travel through the brain.1
The study, published online in Nature Neuroscience on December 2, 2024, used high-pressure frozen electron microscopy to preserve cells in their original state and revealed this previously unrecognized structural detail.1 When axons were exposed to high-frequency electrical stimulation, the beaded regions increased in average length by 8 percent and in width by 17 percent, effects that persisted for at least 30 minutes.1 Correspondingly, the speed of electrical signal transmission slowed following stimulation, with this slowdown lasting at least one hour.1 The team also found that removing cholesterol from the membrane, which makes it more fluid, altered the pearl-like structure and further reduced signal velocity.1 The research was subsequently validated in human brain cortex tissue obtained during epilepsy surgery, with findings published in Neuron in November 2025.1 Since axons measure approximately one one-hundredth the width of a human hair, the beaded structures had long gone undetected in standard microscopy observations.1
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