Neurons can operate in reverse(eurekalert.org) |
Neurons can operate in reverse(eurekalert.org) |
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.
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.
The "classical" synaptic response model was always good at explaining basic signal transmission, but it was essentially stateless. Now we know that neurons are far from stateless, there is extensive chemical modification going on working at different timescales and I guess this "new" discovery is also an important piece that was missing from the standard model. It may explain advanced neuronal states that surpasses simple chemical sensitization and suppression - and it may also provide hints about how feedback works in learning and building internal representations.
ANNs and other AI techniques are getting very good and efficient, but one reason why general artificial intelligence (as in artificial persons) continues to escape us is that we still don't have a good model how the brain organizes and improves itself to form a consistent but autonomously adapting unit which can rightfully be called a mind. I hope that AI people can use these pointers provided by bio research and advance toward this goal.
Be more successful in avoiding predators, acquiring food, mating.
Mother Nature will get every little advantage she could scrounge up.
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 affect the surrounding neurons and may play a role in things like learning and memory.
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.
So sorry, but I don't have primary sources for what I said in my earlier comment...
[1]: http://www.brainsciencepodcast.com/bsp/2010/5/12/exploring-g...
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.
Is it simply a matter of time before we find a quantum computer in there?
And since our brain, like the rest of our bodies, is full of enzymes, I would in no way be surprised if we find other quantum effects.
http://www.brainsciencepodcast.com/bsp/2008/12/6/surprising-...
This is the statement that always comes back to bite biologists. If it's "theoretically possible", biology is probably already doing it somewhere.
"...Maintenance of presynaptic inputs may depend on a post-synaptic factor that is transported from the terminal back toward the soma."
-Neuron: Cell and Molecular Biology (1st edition c 1991)
What was remarkable about this paper was that they demonstrated action potentials (basically, the neuron's relative charge depolarizing) could start not only in the soma, but in the axon.
I'm not familiar with any network-level mechanisms, but there are many local (synapse- or dendrite-level) ones. The one I'm most familiar with is spike-timing dependent plasticity (STDP) [1], which modifies the strength of a synapse based on the millisecond-level timing of action potentials. When cell A tends to fire just before cell B, and the two have synapses connecting them, then cell B will increase the strength of its synapses to A. The reverse is true too: if cell A tends to fire just after cell B, then the synapses will decrease in strength. This is a form of Hebbian learning [2].
[1]: http://en.wikipedia.org/wiki/Spike-timing-dependent_plastici...
There is also 'Hebbian learning', which means that the connections between neurons that fire at the same time become stronger.
Heck, I'd settle for a just a built-in magnetometer or something so I didn't get lost.
(Sorry for the content-free post, I'm feeling slightly more whimsical than usual this Friday afternoon.)
en.wikipedia.org/wiki/Magnetoception#In_humans http://www.isegoria.net/2010/08/does-your-language-shape-how...
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.
You might imagine that the cell would do this by splitting the two DNA strands and sending some molecular machine down each one to replicate it. That is what it does - kind of. See, the tricky part is that the two DNA strands are pointing in opposite directions. The heads and tails of the nucleotides (A, C, T, or G) in each strand are pointed in opposite directions.
You might think that, if evolution can create a machine that works in one direction, it could create a machine that works in the other direction. Then, one could be used on each strand in parallel. Back in the day (~40 years ago), this is basically what everyone assumed must be happening.
But that's not what happens. We only have a machine that goes in one direction. People spent many, many years looking for these little molecular machines, but only ones that went in the same direction were found. None that went backwards.
So for the backwards strand, it's duplicated in a really convoluted process. Basically, instead of copying it all in one shot, it has to repeatedly jump ahead, work back, jump ahead, work back, creating a bunch of little DNA fragments. While it does this, all the little fragments have to be tied together. It's a very strange process.
I wondered to myself whether it was something to do with the very different magnetic declination. No evidence, of course.
I moved back and have regained it again. Mysterious.