Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Neurons can operate in reverse

eurekalert.org

Post reply on HN
Print view View original

11–20 of 33 posts

Re: Neurons can operate in reverse

#11

Post by streptomycin »

busyant wrote: post #4
wladimir wrote: post #3

Earlier quoted context omitted.

Indeed, it seems that some kind of 'backpropagation' does happen in the brain, in contrary to what was always believed. This might have impact on machine learning research.

> contrary to what was always believed This is the statement that always comes back to bite biologists. If it's "theoretically possible", biology is probably already doing it somewhere.

Not really. For instance, people have been looking for 5'-3' DNA polymerase for decades, because it seems like it would be a simpler mechanism for DNA replication than how it really works. But it doesn't seem to exist anywhere.

Re: Neurons can operate in reverse

#12

Post by ihodes »

Here's the Nature paper if anyone's interested (from Dec 2010) http://www.nature.com/neuro/journal/v14/n2/full/nn.2728.html

We had known previously that the axons could send messenger proteins back to the soma (cell body), thus modulating transmitter productions, and could have an inhibitory or excitatory effect on the cell as a whole. We were also aware of axo-axonic synapses, whereby axons could inhibit other axons (among some other things).

EDIT: The above is just extremely brief background of well-known facts about axon messaging.

Re: Neurons can operate in reverse

#15

Post by guscost »

If the network has significant feedback, couldn't these slower "backward" signals be understood in a similar fashion as a fast-moving propeller that appears to reverse direction? I'm curious about how they measured this, but I don't have thirty dollars to spend.

Re: Neurons can operate in reverse

#16

Post by busyant »

streptomycin wrote: post #11
busyant wrote: post #4

Earlier quoted context omitted.

> contrary to what was always believed This is the statement that always comes back to bite biologists. If it's "theoretically possible", biology is probably already doing it somewhere.

Not really. For instance, people have been looking for 5'-3' DNA polymerase for decades, because it seems like it would be a simpler mechanism for DNA replication than how it really works. But it doesn't seem to exist anywhere.

My statement wasn't meant as a disparagement of biologists. Simply that there is a lot of "conventional wisdom" out there in the world that turns out to be false.

When I started grad school (mol bio/genetics), there was a laundry list of things that "never happened in biology". By the time I finished grad school a lot of those items were removed from the laundry list.

And, as I'm sure you're aware, the inability to find something is not evidence that it doesn't exist.

Re: Neurons can operate in reverse

#17

Post by tgflynn »

What I find surprising about this type of news is why the brain would need so much complexity.

It seems to me that a network with 10^11 neurons and 10^14 synapses should have sufficient computational power to carry out the information processing tasks that humans perform using only simple function neurons.

This belief is based on the following observations : - I have personal experience with ANN's with only thousands of nodes that are able to rival humans at handwriting recognition. - Current computers are far from being powerful enough to simulate a 10^14 synapse ANN yet they seem to be rapidly approaching human level performance on many cognitive tasks (ie. Watson).

If individual neurons are as complex as recent research results suggest I wonder what all that computational power is being used for. Or is the human brain just hopelessly inefficient as an information processing machine ? Maybe it's such a recent development that evolution just hasn't had time to get things right.

Re: Neurons can operate in reverse

#19

Post by roc »

tgflynn wrote: post #17

What I find surprising about this type of news is why the brain would need so much complexity. It seems to me that a network with 10^11 neurons and 10^14 synapses should have sufficient computational power to carry out the information processing tasks that humans perform using only simple function neurons. This belief is based on the following observations : - I have personal experience with ANN's with only thousands…

Hazarding a guess... redundancy and adaptability?

Watson's not going to suffer damage to his neurons and still function, nor lose a swath of them permanently, but eventually relearn how to talk.

Nor is it going to be able to ever independently 'learn' a new skill in general.

Re: Neurons can operate in reverse

#20

Post by ihodes »

a-priori wrote: post #6

I didn't think this was new... I remember hearing about this effect last year and having it attributed to Oligodendrocytes, I believe. That said, it's a very important development, because until the last few years the glial cells have mostly been considered to be support cells (e.g. supplying nutrients to the neurons, removing waste products and dead cells, myelinating axons, etc.). But, now we know that they can aff…

This article was from last year (don't know if it's the one you're thinking of), but the paper just theorizes that glia may be involved in the described mechanism.

I think we can be fairly certain that glial cells are involved in neuronal communications, but I'd not say this paper at all proves that.

Post reply on HN