Is the idea that neurons perform ‘computations’ in any way meaningful?

I wrote this up two months ago and then forgot to post it. Since then, two different arguments about ‘computation’ have flared up on Twitter. For instance:

I figured that meant I should finally post it to help clarify some things. I will have more comments on the general question tomorrow.

Note that I am pasting twitter conversations into wordpress and hoping that it will convert it appropriately. If you read this via an RSS reader, it might be better to see the original page.

The word ‘computation’, when used to refer to neurons, has started to bother me. It often seems to be thrown out as a meaningless buzzword, as if using the word computation makes scientific research seem more technical and more interesting. Computation is interesting and important but most of the time it is used to mean ‘neurons do stuff’.

In The Future of the Brain (review here), Gary Marcus gives a nice encapsulation of what I am talking about:

“In my view progress has been stymied in part by an oft-repeated canard — that the brain is not “a computer” — and in part by too slavish a devotion to the one really good idea that neuroscience has had thus far, which is the idea that cascades of simple low level “feature detectors” tuned to perceptual properties, like difference in luminance and orientation, percolate upward in a hierarchy, toward progressively more abstract elements such as lines, letters, and faces.”

Which pretty much sums up how I feel: either brains aren’t computers, or they are computing stuff but let’s not really think about what we mean by computation too deeply, shall we?

So I asked about all this on twitter then I went to my Thanksgiving meal, forgot about it, and ended up getting a flood of discussion that I haven’t been able to digest until now:

(I will apologize to the participants for butchering this and reordering some things slightly for clarity. I hope I did not misrepresent anyone’s opinion.)

The question

Let’s first remember that the very term ‘computation’ is almost uselessly broad.

Neurons do compute stuff, but we don’t actually think about them like we do computers

Just because it ‘computes’, does that tell us anything worthwhile?

The idea helps distinguish them from properties of other cells

Perhaps we just mean a way of thinking about the problem

There are, after all, good examples in the literature of computation

We need to remember that there are plenty of journals that cover this: Neural Computation, Biological Cybernetics and PLoS Computational Biology.

I have always had a soft spot for this paper (how do we explain what computations a neuron is performing in the standard framework used in neuroscience?).

What do we mean when we say it?

Let’s be rigorous here: what should we mean?

A billiard ball can compute. A series of billiard balls can compute even better. But does “intent” matter?

Computation=information transformation

Alright, let’s be pragmatic here.

BAM!

Michael Hendricks hands me my next clickbait post on a silver platter.

Coming to a twitter/RSS feed near you in January 2015…

 

The bigger problem with throwing the word ‘computation’ around like margaritas at happy hour is it adds weight to

Monday Open Thread: The Six Problems of Systems Neuroscience

I was brainstorming experiments and decided to make a list of what I think are the fundamental questions in systems neuroscience:

  1. Sensory: How do we represent the world?
  2. Motor: How do we create an action?
  3. Decision: How do we choose among competing alternatives?
  4. Learning: How do we remain plastic in changing environments?
  5. Computation: What are the underlying algorithms and computations?
  6. Modulation: How does internal state affect the nervous system?

Can anyone think of other broad questions in systems neuroscience? Should one of these not be here? Most other things I could think of belong here; for instance, “How do we deal with external and internal noise?” would probably be under Sensory or Learning. AYWNMBTTOF wrote a great post on what he considers the big questions of his field (taste) which I would subsume under Sensory.

I kind of hope this replaces the somewhat useless 23 Problems in Systems Neuroscience in terms of clarifying what we are studying.