Neuronal Communication

Or: Is the Brain Analogue or Digital?

Until very recently — historically speaking — we had less than no idea how the body worked.

If it were not for the chance twitching of a frog’s legs in 1780, when they brushed against a metal rail in Luigi Galvani’s laboratory, we might still be none the wiser. That accidental twitch set off a line of inquiry that eventually revealed something rather shocking:

We soggy-biocritters run on electricity.

Not quite the sort you find in your wall socket. In modern electronics, electricity is mostly electrons wandering along copper wires. In biological systems, the “wires” are nerves, and the moving charge is carried by ions — atoms that have gained or lost an electron and now travel with attitude.

So yes, we use electricity. But ours comes with transport. The electrons hitch a ride on friendly ions.

Of course, real neural networks are billions of times more complex than any simple diagram. But here’s the real cruncher.

With only a few oddball exceptions, nerves in the body are firing all the time.

Yes. All the time.

Sensors such as eyes, ears, and thermoreceptors are not silent until stimulated. They idle. Like a car engine running at a red light. When the environment changes, the system doesn’t switch on — it speeds up or slows down.

That’s the trick.

A Warm Example

Imagine a temperature-sensing cell — a thermoreceptor.

These cells have little molecular doorways in their membranes called ion channels. When temperature changes, these doorways open more or less, allowing ions — often sodium or calcium — to flow into the cell.

That flow alters the electrical potential across the cell membrane. When the change is large enough, the neuron fires an electrical impulse. That impulse travels up the spinal cord to the brain, eventually reaching the post-central gyrus of the primary somatosensory cortex in the parietal lobe.

(I warned you there would be a bit of anatomy. You’re doing fine.)

Here’s the key:

Cold → fewer ions entering → fewer nerve impulses per second

Warm → more ions entering → more nerve impulses per second

The strength of the stimulus is not encoded in the size of the signal. It is encoded in the frequency of firing.

That distinction matters enormously.

Enter Radio

In radio engineering, this would be called Frequency Modulation — FM.

The information is carried in changes in frequency, not amplitude.

Early radio systems used Amplitude Modulation (AM). The sound wave changed the height (voltage or magnitude) of the carrier signal. Later, Edwin Armstrong showed that encoding sound as tiny shifts in frequency (Frequency Modulation FM) produced far clearer transmission.

Here’s the delicious irony:

Soggy-biocritters were using frequency modulation long before radio engineers worked it out.

Right out of the evolutionary box.

☞ (Insert preferred cosmology here.)

The Digital Twist

Here’s the mind-bender.

There is no such thing as a “big” or “small” nerve impulse.

An action potential either happens or it doesn’t. It is all-or-nothing.

That makes each nerve impulse digital.

But the pattern of impulses — the spacing between them — varies continuously with temperature, light, sound, pressure…

That part is analogue.

So is the brain analogue or digital?

Yes.

Individual spikes are digital. The timing between them is analogue. Meaning the nervous system is a frequency-coded hybrid machine — a biological FM network wired with living tissue.

The Difference Engine

There’s one more elegant consequence.

Because neurons idle, the brain is not measuring absolutes. It measures differences from baseline.

Step on the gas — firing rate increases. Ease off — firing rate decreases.

Your brain is a difference detector. A change detector. A signal-over-noise engine.

Which leads, naturally, to habituation — what happens when a signal stops changing.

But that is a story for another day.

That was Signal Over Noise for today.