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

January 2015 in review (personal)

Warning: random personal crap

So I’m trying to keep track of my life this year. We’ll see how that works out. I have a lot of data on my phone that I need to figure out how to get onto the computer.

This month I (re)submitted a manuscript and worked on learning basic grammar. I am trying to learn Tamil and can finally read the characters of the alphabet, and have been improving my vocab.

Poems memorized

When I have dreams that I may cease to be (Keats)

When I have fears that I may cease to be
Before my pen has gleaned my teeming brain,
Before high-pilèd books, in charactery,
Hold like rich garners the full ripened grain;
When I behold, upon the night’s starred face,
Huge cloudy symbols of a high romance,
And think that I may never live to trace
Their shadows with the magic hand of chance;
And when I feel, fair creature of an hour,
That I shall never look upon thee more,
Never have relish in the faery power
Of unreflecting love—then on the shore
Of the wide world I stand alone, and think
Till love and fame to nothingness do sink.

Movies

The Raid 2, John Wick – Let’s talk about these together because they, along with Snowpiercer and Edge of Tomorrow, are by far the best action movies to come out this year. The Raid 2 had some pretty amazing cinematography and fight scenes but it tried to have a story, too. And, I’m sorry, that story really failed. But still: a flawed classic. John Wick knew what it wanted to be and went with it. It also did some things I’ve never seen in an action movie before.

Big Hero 6  – Meh. A bit of a disappointment; just go watch The Incredibles again, instead.

The Trip to Italy – Like The Trip, only in Italy and now Steve Coogan is happy while Rob Brydon is depressed. I loved it.

Birdman – Is there any doubt that this will win the Best Picture Oscar? What does Hollywood like better than movies about themselves? Movies that portray Hollywood as superior to Broadway, that’s what. A really great movie with great performances.

Big Eyes – I have a really hard time with Amy Adams and I can’t quite tell you why. A fun story with the feel of classic era-Tim Burton. Probably a better movie to watch in the background than to focus on closely, though, because nothing is subtle.

American Sniper – I don’t understand who can watch this and think it is pro-military?! The main character is clearly flawed and has PTSD, and gets more and more screwed up as the movie goes on. The ending scenes (the battle, him at home) seemed perfunctory and cliched, and the whole sniper v sniper thing was ridiculous.

Whiplash – If you ever have had any desire to “be great”, watch this movie. Absolutely phenomenal. Out of my top five movies of the year (see below), this is the one I am most likely to watch repeatedly.

Under The Skin – Another surprising movie that was slow but – to me – did not seem slow. Beautiful and haunting performances that kept building on each other.

Performance – A cockney gangster goes in hiding in Mick Jagger’s basement. As strange as it sounds. You can tell that you are watching the cusp of the 60s die away, here.

Starred Up – Jack O’Connell was far and away the most charismatic actor that appeared on Skins. His performance here is haunting and scary and terrifyingly sad. You have to watch this.

Ida – Not a lot happens, per se, but if you printed out any given frame of the movie and put it on your wall? It would be the most beautiful thing on your wall.

Adventures in Babysitting – 80s, yay! Suburban kids go on wacky adventure to the big scary city.

Selma – LBJ is my man. He is the only person I took a photo with at the Wax Museum. But you know what? Every other biopic changes things for the sake of narrative and of the ones I have seen this year it is far from the worst offender at that. It’s a movie, not a documentary! I loved a lot of the performances – was the MLK Jr. actor amazing, or what? – but some of the directoral choices made me roll my eyes.

Four Weddings and a Funeral – Somehow hadn’t seen this before. What ever happened to Hugh Grant? Besides prostitutes, that is. This movie was funny, ha ha, you know, British stuff. I understand why it’s a classic.

Fried Green Tomatoes – Kind of The Shawshank Redemption but female and in the South.

Pontypool – A fantastic take on the Zombie movie; the main character is a radio DJ shock jock trapped in his studio while the world goes to hell outside. I think it may be a commentary about French Canadians but not sure. Also the best depiction of phonotaxis I have ever seen.

Minor thoughts (not a movie title)

It was a great year for movies – I think I saw more that I loved this year than I have in the past few years combined. There seemed to be five movies that were clearly better than the others this year (imho): Boyhood, Birdman, Whiplash, Under The Skin, and Starred Up. Whiplash, as I said, is the only one I am likely to watch again multiple times; maybe I would watch Boyhood or Under The Skin once or twice over the next five or ten years. But Birdman will win all the Oscars… Nightcrawler should have been on this list – especially for me: it ticks all of my boxes (intensely dark, LA at night, a performance for the ages from Gyllenhaal) – but it throws away all of its promise with some really bad direction/editing and some terrible terrible music.

Books

The Lies of Locke Lamorra/Red Seas Under Red Skies – Lies is basically Fritz Leiber set in an Italian city-state (“Camorr”), but better (I was never a big fan of Fafhrd for some reason). It was definitely one of those “can’t put it down” books. Red Seas tried to pull it off again but it was bloated and slow and lacked suspense.

MFA vs NYC – Background here is an article claiming the MFA programs are ruining American fiction through homogenization. This book is a collection of essays exploring the topic. Ironically, the essays by the MFA writers all argue against this idea, but they all write the same! The writing is generally better by the MFA writers but the best essays were by those who came out of the NYC community (higher variance, lower mean, perhaps). But the MFA writers all have somewhat okay jobs compared to the NYC writers who, god, just don’t have any money ever and their lives sound terrible. 10/10 would not be a NYC writer.

Adulting – Tips on being an adult. My parents had this lying around the house when I visited for some reason. Lots of good tips, though mostly if you are around ~22. I’m a few years old for some of them… but it’s well-written and funny.

Both Flesh and Not – I have not read much DF Wallace so this was a pretty big disappointment. I hear it was a money grab for his estate after he died, and I hope so because these were mostly boring and not good. Mostly substitute facts for knowledge or insight. I did appreciate the formal experimentation he did, though the excessive footnotes can drag pretty heavily and could be done much better.

Tamil Pulp Fiction – A translated collection of stories from Tamil Nadu (India). Most of them are pretty similar (the good guy wins!) but pulp stories have a lot of insight into the local culture. I enjoyed about half of them, which is good enough when they are fast reads.

Jack of the Shadows – Zelazny trying to be Vance. I haven’t read any Zelazny since middle school, maybe? So I can’t really compare to his other writing. But it lacks some of the subtlety and all of the wit that characterizes Vance. Think of it as Vance trying to be a bit more conventionally-fantasy.

The caveman who accidentally invented human chronobiology

A great interview from someone who lived in a cave for months on end:

 You have to understand, I was a geologist by training. In 1961, we discovered an underground glacier in the Alps, about seventy kilometers from Nice. At first, my idea was to prepare a geological expedition, and to spend about fifteen days underground studying the glacier, but a couple of months later, I said to myself, “Well, fifteen days is not enough. I shall see nothing.” So, I decided to stay two months. And then this idea came to me—this idea that became the idea of my life. I decided to live like an animal, without a watch, in the dark, without knowing the time…

There was a very large perturbation in my sense of time. I descended into the cave on July 16 and was planning finish the experiment on September 14. When my surface team notified me that the day had finally arrived, I thought that it was only August 20. I believed I still had another month to spend in the cave. My psychological time had compressed by a factor of two…

Interestingly, during the subsequent experiments I did with other research subjects, all of the people in the caves showed cycles longer than twenty-four hours. In fact, it became common for them to achieve cycles lasting forty-eight hours: They would have thirty-six hours of continuous activity followed by twelve to fourteen hours of sleep. After we made that discovery, the French army gave me lots of funding. They wanted me to analyze how it would be possible for a soldier to double his wakeful activity.

And why we couldn’t do this now:

The experiments in the caves are finished. You can’t do these kinds of experiments any more. When we first did them, I was young, and we took all the risk. Now, there are limitations on researchers. Now you have ethics panels. Let me give you an example. In 1964, the second man after me to go underground had a microphone attached to his head. One day he slept thirty-three hours, and we weren’t sure if he was dead. It was the first time we’d ever seen a man sleep for that long. I thought, okay, I’ll descend into the cave and find out what happened. And then at thirty-four hours, he snored, and we understood he was alive. And then a couple minutes later, he called us at the surface to take his pulse. Today, doctors would have to wake him up because it would be too risky to do otherwise.