A butterfly effect in the brain

Jun 30, 2010
Brain

Next time your brain plays tricks on you, you have an excuse: according to new research by UCL scientists published today in the journal Nature, the brain is intrinsically unreliable.

This may not seem surprising to most of us, but it has puzzled neuroscientists for decades. Given that the brain is the most powerful computing device known, how can it perform so well even though the behaviour of its circuits is variable?

A long-standing hypothesis is that the brain's circuitry actually is reliable - and the apparently high variability is because your brain is engaged in many tasks simultaneously, which affect each other.

It is this that the researchers at UCL tested directly. The team - a collaboration between experimentalists at the Wolfson Institute for Biomedical Research and a theorist, Peter Latham, at the Gatsby Computational Neuroscience Unit - took inspiration from the celebrated butterfly effect - from the fact that the flap of a butterfly's wings in Brazil could set off a tornado in Texas. Their idea was to introduce a small perturbation into the brain, the neural equivalent of butterfly wings, and ask what would happen to the activity in the circuit. Would the perturbation grow and have a knock-on effect, thus affecting the rest of the brain, or immediately die out?

It turned out to have a huge knock-on effect. The perturbation was a single extra 'spike', or , introduced to a single neuron in the brain of a rat. That single extra spike caused about thirty new extra spikes in nearby neurons in the brain, most of which caused another thirty extra spikes, and so on. This may not seem like much, given that the brain produces millions of spikes every second. However, the researchers estimated that eventually, that one extra spike affected millions of neurons in the brain.

"This result indicates that the variability we see in the brain may actually be due to noise, and represents a fundamental feature of normal ," said lead author Dr. Mickey London, of the Wolfson Institute for Biomedical Research, UCL.

This rapid amplification of spikes means that the brain is extremely 'noisy' - much, much noisier than computers. Nevertheless, the brain can perform very complicated tasks with enormous speed and accuracy, far faster and more accurately than the most powerful computer ever built (and likely to be built in the foreseeable future). The UCL researchers suggest that for the brain to perform so well in the face of high levels of noise, it must be using a strategy called a rate code. In a rate code, neurons consider the activity of an ensemble of many neurons, and ignore the individual variability, or noise, produced by each of them.

So now we know that the brain is truly noisy, but we still don't know why. The UCL researchers suggest that one possibility is that it's the price the brain pays for high connectivity among (each neuron connects to about 10,000 others, resulting in over 8 million kilometres of wiring in the human brain). Presumably, that high connectivity is at least in part responsible for the brain's computational power. However, as the research shows, the higher the connectivity, the noisier the . Therefore, while noise may not be a useful feature, it is at least a by-product of a useful feature.

Explore further: Safe driving period calculated following first-time seizure

More information: The paper 'Sensitivity to perturbations in vivo implies high noise and suggests rate coding in cortex' is published in Nature on Wednesday 30 June 2010.

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droid001
not rated yet Jun 30, 2010
The question is - how the brain makes decisions in this noisy enviroment? Who decided that the task performed?
Jigga
not rated yet Jun 30, 2010
I do believe, brain is behaving like simulator of quantum reality or "pocket universe". By concept of "liquid computing" developed by Swiss neuroscientists the brain works like a pond in which stones are thrown. The waves caused by this perturbation don't disappear immediately, but rather overlap with each other and collect information about how many stones were thrown in and how big they were. The main difference is just that the waves in the brain spread in a network of neurons and at very high speed. By excellent Hebbian theory of synaptic plasticity this aspect of soliton behavior is represented by principle "cells that fire together, wire together". When one cell repeatedly assists in firing another, the axon of the first cell develops synaptic knobs (or enlarges them if they already exist) in contact with the soma of the second cell. In this mechanism the principle of associative learning and long-term memory.
Jigga
not rated yet Jun 30, 2010
Who decided that the task performed?
Even in noisy environment you're able to follow the path of maximal noise intensity. I presume, human brain works in the same way: the most loaded neurons or synapses are becoming the preferred path for another spikes, which creates a positive feedback gradually.

Whenever the critical level is reached, all future spikes will follow newly defined path - and a brain will use it as a predefined solution for future.

This aspect of behavior of neural network is similar to quantum foam, which becomes the more dense, the more energy is spreading through it, until some quantized stable particle emerges. I do believe, inside of our brain the stable hyperdimensional artifacts similar to branes and spin loops are surviving. One of such loops was identified already inside of human brain as a source of our private internal clock - it enables us to estimate time intervals.
droid001
not rated yet Jun 30, 2010
"Liquid computing"? It is only a technical definition, it does not explain anything. How the brain forms perception and decisions from those chaotic waves?
I know, it's a "hard problem".
Jigga
not rated yet Jun 30, 2010
..how the brain forms perception and decisions from those chaotic waves?
As I told already, neurons have properties of quantum foam, which becomes the more dense, the more energy is spreading through it. The groups or neurons who are exchanging spikes in synchrony are becoming an easier target for another spikes. This is metastable state: such neurons are actually collecting information from their neighborhood in the same way, like rogue waves at ocean surface. We can say, they're fighting for it like animals in process of natural evolution.

At the moment, when critical level is reached, the spontaneous symmetry breaking occurs - the information spreading virtually condenses along effective neurons. Actually brain remembers the most successful neurons probably by residual concentration of neurotransmitters and during sleeping it forms a permanent connections - a new synapses - between most effective neurons.

Next day these neurons will be used as a preferred reflexion path.
Jigga
not rated yet Jun 30, 2010
To maintain positive feedback required for selforganization of spikes inside of human brain, the surface of neurons must be kept at its quantum critical point. Their membranes are having a nature of liquid crystal - they contain "cracks" and domains perpendicular to membrane crossection, thus increasing the dimensionality of neuron. If this membrane melts, the neuron will lose its ability to spread neural signals at all. This is why we cannot swim or move in cold water and why crocodile must be warmed, before it can catch and eat you.

Neurons increase the dimensionality further by their internal foamy structure composed of microtubules. I presume, these microtubules are working in the same way, like the hollow core optical fibers - they're just using sound signal instead of light. This construction feature enables to propagate spikes as a non-dispersing solitons along neuron, where they can collect and merge with another solitons.
canuckit
not rated yet Jun 30, 2010
Could we add that since women are prone to multitasking and men tend to do one thing at the time linearly in time, is the female brain intrinsically more unreliable than the male brain?
Arthur_Zombie
not rated yet Jun 30, 2010
Now I would like to see them run this experiment on the rats that practice mindfulness meditation...
fleem
5 / 5 (2) Jun 30, 2010
This article is written as if "noise" and "amplification" mean the same thing. They don't.

The brain has many paths of positive feedback (and when left unchecked, result in a seizure), and certainly the brain will have some degree of noise and be designed to handle and even take advantage of that noise (for example, noise can cause a non-linear process like a synapse to act more like a linear process through pulse width modulation). But this article seems to muddle all these concepts.
alt_whitman
not rated yet Jun 30, 2010
"from the fact that the flap of a butterfly's wings in Brazil could set off a tornado in Texas."

Ah, sorry. A silly cliche is by no means the same thing as a fact.
Syntience
not rated yet Jun 30, 2010
We've assumed for a while that the brain is unreliable. Synapse signaling uses diffusion of neurotransmitters across the synaptic gap and multiple factors determine the detection threshold. The brain is massively parallel so there will be numerous race conditions that affect all neural activity. So the brain has developed sufficient redundancy to operate well in spite of these problems.

This robustness against internal errors directly translates into resilience against errors in input. Phrased differently, because the brain *is* unreliable and evolved to operate in spite of that, it is more resilient against misinformation on the incoming senses such as problems with photoreceptors in the eye, visual and auditory mistakes and illusions. But also all the way up the chain to where the brain is well suited at the semantic level to detect lies and misinformation.

I discuss this in the video "Bizarre Systems" at http://videos.syntience.com
Jigga
not rated yet Jul 01, 2010
Although the human brain represents only 2% of the body weight, it receives 15% of the cardiac output, 20% of total body oxygen consumption, and 25% of total body glucose utilization. It's roughly 30 - 150 W of energy in the form of less or more organized motion of charged particles (ions) in high dimensional structures.

According to some hobbyists, if you design your coil with a caduceus pattern -- i.e., with two opposing sets of windings that cross each other twice per revolution such that their magnetic fields precisely cancel -- the resulting device will radiate highly directional "scalar waves" which are undetectable with ordinary radio equipment but receivable with another caduceus coil perfectly aligned with your first. If it's true, it could be serve as a physical basis of telepathy.

http://en.wikiped...lar_coil

Actually, I never found some peer-reviewed literature, confirming or refuting this effect. But it may be consistent with Aharamov-Bohm effect of QM.
abhishekbt
not rated yet Jul 02, 2010
"from the fact that the flap of a butterfly's wings in Brazil could set off a tornado in Texas."

Ah, sorry. A silly cliche is by no means the same thing as a fact.


Try searching for the Butterfly Effect. You will find that other than a movie name it is also a quite known fact among scientists and researchers.

In particular, guys involved with simulation and other heavy computational activities.
Milou
not rated yet Jul 03, 2010
I always though the brain does not want to be discovered and therefore produces all kinds of noise (spikes...). This "brain machine" being inside humans, we react to all kinds of acts including research to discover self. But the brain will expand (trick us) before we can grasp our meaning. Movie maker!!!
MadPutz
not rated yet Jul 05, 2010
I have no control of my brain. It's rote chemical reactions control me.