In 1971, Ian Waterman suddenly collapsed from a severe case of what seemed to be gastric flu.
1971 年，伊恩·沃特曼突然病倒，他以为是肠胃炎导致的。
His illness passed after a few days, but a stranger set of symptoms lingered.
几天后，症状消退了，但他感到身体有些异样。
Although his muscles and joints remained healthy, Waterman was unable to move.
尽管沃特曼的肌肉和关节状况良好，但他无法移动身体了。
In fact, he was unable to feel anything from the neck down.
实际的状况是：他从脖子以下没有任何感知。
Eventually, he was diagnosed with a rare and extreme form of deafferentation,
最后，他被诊断患了一种极其罕见的传入神经阻滞疾病，
a neurological condition in which certain signals from the nervous system are interrupted or impaired.
这是一种神经系统疾病，这意味着神经系统中的部分传输信号中断或受到了损伤。
Without his body's constant feedback on how his limbs were moving, Waterman was unable to sit up, stand, or walk.
由于沃特曼失去了四肢活动时惯常的感知，他无法坐、无法站、也无法走路。
But over time, he taught himself to use sight to judge the distance of his limbs from other objects.
但多年后，他逐渐学会了使用目光来判断自己的肢体与其他物体之间的距离。
And eventually he regained complete control of his body— so long as he could see it.
最终，他又重新获得了自由移动身体的能力，前提是他能看见周围的事物。
We often don't think of touch as being a vital part of movement.
我们一般不会认为触觉在日常生活中起到多大作用。
But touch is just one part of the somatosensory system,
虽然触觉仅仅只是躯体感觉系统的一部分，
a network that oversees all the sensations arising from the surface and interior of our bodies.
呈网络状，但统筹着身体表面与身体内部产生的所有感觉。
Touch, pain, temperature, and our awareness of our bodies in space— also known as proprioception— are regulated by this system.
我们的触觉、痛感、体温和空间感知统称为本体感觉， 也是由躯体感觉系统来调节的。
And when something goes wrong, the effects can be dramatic.
当哪个部分出了问题时，会对人体产生巨大的影响。
All these sensations are processed by millions of tiny receptor cells embedded in our skin, muscles, tendons, and organs.
成千上万微小的受体细胞处理着所有这些感觉，深入我们的皮肤、肌肉、 肌腱和各个器官。
Every square centimeter of our skin is packed with hundreds of these cells, and their shape, size,
我们身上每平方厘米皮肤都充满了成百上千个这样的细胞，这些细胞的形状、大小
and depth determine what kind of stimuli they respond to.
和厚度决定了这些细胞对哪种刺激有反应。
Mechanoreceptors sense mechanical deformation of the skin.
机械感受器感知皮肤的机械变形。
This could be triggered by low or high frequency vibrations, a stretch, or simply light, static pressure.
这可能会由低频或高频的感受、拉伸，或仅仅由轻微的静态压力所引发。
Thermoreceptors respond to temperature changes, while nociceptors sense pain.
温度感受器对温度变化有反应，而伤害感受器会感知到疼痛。
And propriocepters sit deep in your muscles and tendons, continually detecting and relaying information about the position of your body.
本体感受器存在于肌肉和肌腱底层，持续不断地探测传递与身体位置相关的信息。
Your brain then combines this information with other sensory data to move through space without needing to see your limbs.
然后，大脑就会将这类信息与其他感官数据结合，让人可以在空间中自由移动，而不用看见肢体的位置。
All of these receptors work by sending electrical signals to the brain through fibers they're attached to.
所有这些感受器通过向大脑发送电信号来工作，经由所依附的神经纤维。
And the speed of those signals varies with the fiber's thickness.
这些信号的速度与神经纤维的厚度有关。
For example, some nociceptors are attached to fibers with slightly more conductive, fatty myelin than others.
例如，一些伤害感受器附着在比其他感受器更具导电性的脂肪髓鞘的纤维上。
So when you get hurt, the electrical impulses from thicker nociceptors trigger sharp, intense pain,
所以当你受伤时，具有更厚质的伤害感受器所传导的电脉冲就会引发强烈的剧痛，
while thin, unmyelinated nociceptors are responsible for the dull, aching pain that follows.
而薄质且无髓鞘的伤害感受器则会产生隐隐的酸痛。
And since the fibers carrying tactile information are much thicker than those carrying nociceptive signals,
而且由于带有触觉信息的神经纤维比带有损伤性信号的纤维要更厚一些，
rubbing an injury can produce temporary relief from the pain.
摩擦伤口反而可能暂时不会那么疼。
These receptors generate a constant flood of signals that travel through the nervous system to the brain.
这些感受器会产生持续的信号流，通过神经系统传输到大脑。
But if this process is disrupted— either by damage to the skin, the nerves, or the brain— the network breaks down.
但如果这个过程受到干扰，不管是皮肤受伤，还是神经或大脑受到了损伤，这种信号传输的过程就无法进行。
And since it underpins so many bodily functions, damage to the somatosensory system can manifest in a wide variety of ways.
而且由于很多身体功能都依赖于这种信号传输，因此对躯体感觉系统的损害可以通过多种方式表现出来。
In Waterman's case, an autoimmune reaction attacked a large swath of his nervous system,
在沃特曼这个案例中，自身免疫反应攻击了他大部分的神经系统，
leaving him with no tactile or proprioceptive sensations from the neck down.
使他从脖子以下就失去了触觉或本体感觉。
But deafferentation is just one of many somatosensory disorders.
但传入神经阻滞仅仅只是许多躯体感觉失调的情况之一。
Individuals can receive damage to a specific brain area or a section of skin, resulting in the loss of certain sensations in particular locations.
个体的脑部区域或部分皮肤可能受到损伤，导致丧失特定部位的感觉。
And the impact of this loss can be significant.
这种感觉的丧失会对人体产生非常大的影响。
Losing tactile sensations makes it difficult to gauge how much strength to use in a situation.
丧失触觉会让人在具体情境中判断使用多少力气变得非常困难。
Without the warning signals provided by thermal and pain stimuli, we don't react when our bodies are damaged.
如果没有体温或痛感的刺激来提醒我们引起注意，身体在受到损伤时，我们就不会做出相应的反应。
And, being deprived of social touch can cause a condition known as touch starvation, characterized by anxiety, depression, high blood pressure,
并且，由于缺乏与他人的社会交往，导致“触摸匮乏”的情况发生，主要表现为焦虑、抑郁、高血压，
and even a weakened immune system.
甚至还会出现免疫力下降这样的情况。
Many individuals who face these realities have found innovative ways to adapt.
许多患者采用了一些新的方式来适应这种情况。
But it's undeniable that all these invisible sensations play a vital role in how we navigate the world— even if they can be difficult to put your finger on.
但不可否认的是， 所有这些无形的感觉在我们探索世界的过程中，起到了非常重要的作用，即使这些感觉可能很难说清楚。
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