Representational Drift

Here's a puzzle for any materialistic view of our cognitive experience, i.e. any view that posits the material brain and sense organs as the sole entities responsible for cognition and sensation. The puzzle has to do with something called "representational drift." An article in The Atlantic elaborates:

Neuroscientists have held the view that different sensations, smell, sight, taste, etc., stimulate specific groups of neurons in the brain. These patterns of neural firing - called representations - were thought to remain the same from one moment to the next.

The group of neurons that fired when you smelled a rose yesterday are the same group of neurons that will fire when you smell the rose again today.

The explanation found in neuroscience textbooks is that specific groups of neurons fire when their owner "smells a rose, sees a sunset, or hears a bell. These representations—these patterns of neural firing—presumably stay the same from one moment to the next."

But a team of researchers at Columbia University have discovered a strange thing. The researchers...

allowed mice to sniff the same odors over several days and weeks, and recorded the activity of neurons in the rodents’ piriform cortex—a brain region involved in identifying smells. At a given moment, each odor caused a distinctive group of neurons in this region to fire.

But as time went on, the makeup of these groups slowly changed. Some neurons stopped responding to the smells; others started. After a month, each group was almost completely different.

Put it this way: The neurons that represented the smell of an apple in May and those that represented the same smell in June were as different from each other as those that represent the smells of apples and grass at any one time.

...other scientists have shown that the same phenomenon, called representational drift, occurs in a variety of brain regions besides the piriform cortex. Its existence is clear; everything else is a mystery.

[The researchers] don’t know why it happens, what it means, how the brain copes, or how much of the brain behaves in this way. How can animals possibly make any lasting sense of the world if their neural responses to that world are constantly in flux?

If such flux is common, “there must be mechanisms in the brain that are undiscovered and even unimagined that allow it to keep up. Scientists are ... in this particular case, ... deeply confused. We expect it to take many years to iron out.”

How does the brain know, the article asks, what the nose is smelling or what the eyes are seeing if the specific neurons which respond to smells and sights are continuously changing?

A deeper question, perhaps, is how and why would such complexity of function arise in a purely materialistic world in which blind Darwinian processes like genetic mutation and natural selection are responsible for the structure and function of our brains? What survival value would it have?

This kind of multi-functionality is the sort of thing we see intelligent minds design, but it's not what we'd expect to result from random accidents like genetic mutations.

I don't want to draw too many conclusions from all this, but I will say that it seems like every discovery scientists are currently making about our world and about living things makes it harder to cling to both materialism and the naturalism (the belief that the natural world is all there is) that undergirds it.