Travelling at the speed of thought

Discover Magazine has an excellent Carl Zimmer piece discussing efforts to understand the speed of the human nerves – a quest that has lasted for well over one hundred years.

Although our experience of the world seems instantaneous, different nerves in the body work at different speeds and, of course, cover different distances – to the point where taller people experience a slight sensory lag compared to shorter people owing to the greater length of some of the nerve pathways.

Speed is not necessarily of the essence, however, and as with dancing, it is timing and co-ordination that seems key:

Sometimes our brains actually need to slow down, however. In the retina, the neurons near the center are much shorter than the ones at the edges, and yet somehow all of the signals manage to reach the next layer of neurons in the retina at the same time. One way the body may do this is by holding back certain nerve signals—for instance, by putting less myelin on the relevant axons. Another possible way to make nerve impulses travel more slowly involves growing longer axons, so that signals have a greater distance to travel.

In fact, reducing the speed of thought in just the right places is crucial to the fundamentals of consciousness. Our moment-to-moment awareness of our inner selves and the outer world depends on the thalamus, a region near the core of the brain, which sends out pacemaker-like signals to the brain’s outer layers. Even though some of the axons reaching out from the thalamus are short and some are long, their signals arrive throughout all parts of the brain at the same time—a good thing, since otherwise we would not be able to think straight.

Link to Discover article ‘What Is the Speed of Thought?’

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