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First Movie of an Entire Brain's Neuronal Activity
KentuckyFC (1144503) writes "One of the goals of neuroscience is to understand how brains process information and generate appropriate behaviour. A technique that is revolutionising this work is optogenetics--the ability to insert genes into neurons that fluoresce when the neuron is active. That works well on the level of single neurons but the density of neurons in a brain is so high that it has been impossible to tell them apart when they fluoresce. Now researchers have solved this problem and proved it by filming the activity in the entire brain of a nematode worm for the first time and making the video available. Their solution comes in two parts. The first is to ensure that the inserted genes only fluoresce in the nuclei of the neurons. This makes it much easier to tell individual neurons in the brain apart. The second is a new techniques that scans the entire volume of the brain at a rate of 80 frames per second, fast enough to register all the neuronal activity within it. The researchers say their new technique should allow bigger brains to be filmed in the near future, opening up the potential to study how various creatures process information and trigger an appropriate response for the first time."
So many questions.
Could a complete mapping of the neural network be accomplished?
Would it be possible to artificially trigger a neuron to verify the mapping?
If that captures everything, that's the interesting part to me(though I'm sure it's been known to actual neurologists forever). That means the "clock speed" of the human brain is really really really really low, more or less, right? Like our consciousness is pretty much exclusively the result of massive parallelism?
Siskel gave it two thumbs down.
Here you go, direct link to the YouTube upload.
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Do neurons just fire or not fire in a binary fashion, or are there different levels/voltages of on and off?
And we finally know what nematodes are thinking: http://i1.ytimg.com/vi/GpEDsoZ...
There is no clock speed. It is asynchronous and analog. Even if it had some kind of natural timing to it, some things will fire faster others slower. Chained signals will have delays along the path. The result is something without any clock speed with operations happening at the speed of analog (as fine grained as the physics allows... so in other words, crazy fast to capture it all in digital.)
Absolute precision will not be required just as analog audio doesn't need to be converted at the rate the individual molecules move and as they differ -- that level of detail is "noise" even if it is not actual random noise. You can get plenty good approximations with a decent sampling rate... but for this kind of stuff I doubt it's even 200Hz let alone 80Hz. The degree of the signal sent by neurons is not binary... so if you were thinking maybe it's 8bits... somehow I can't see how creatures which can hear better than 8bit 11 Khz audio would think at a slower rate. (ok i realize the ear is physically doing the FFT so the brain only gets the spectrum.)
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The entire brain of a nematode worm??? You don't say!!!
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Its amazing:
For example a human can recognize the picture of another person in about 100 ms. Given the processing time of 1 ms for an individual neuron this implies that a certain number of neurons, but less than 100, are involved in serial; whereas the complexity of the task is evidence for a parallel processing, because a difficult recognition task can not be performed by such a small number of neurons, example taken from [zell94, p24,]. This phenomenon is known as the 100-step-rule.
it would be a one-reeler.
KentuckyFC, you seem to need a trademark license to use that username... where'd you get that from?
They record calcium activity in neurons. Calcium is a marker of neuronal activity (although the dynamics are slower than electrical ones). Calcium recording in the nematode is difficult, because the neurons are small, and the spread of calcium is very broad. The method is impressive and a great breakthrough. However...
1. A brain is a center of the nervous system. It's not strictly correct to speak of brains of nematodes. They don't have this separation of their nervous system. In the article they write of the anterior nervous system of the nematode, and say that their technique could be applied to brains of other animals. 2. The short clip is not a recording of all neurons. It's 70% of the neurons contained in the head ganglia.
Some people here speak of the mapping of the network. This was already done in 1986. The nematode is highly stereotypic. It's known what neurons there are (they all have acronyms), how many, and what they are connected to. The weight of these connections is not clear yet however. What is not clear are the associated neurotransmitters to these synapses and the strength of synapses. This determines how strongly neurons modulate each other and if the modulation is excitatory or inhibitory.
With some caveats in place, the potential of the recordings based on this technique is to help to get to the connection strengths, and to a functional connection diagram that then can potentially be used for predicting the animals behavior.
Neuroscience is a whole field dedicated to learning how the brain works. Do you really think that there has never been a video made of whole-brain neuronal activity? Ever heard of fMRI? That's the most common way to track activity over time, which - guess what - makes a video. There are many other imaging modalities which can be used to measure activity over time.
It's the first time this method was used to make a whole-brain record of activity. And it's cute that it uses visible light instead of magnetism or radioactive decay, but that certainly doesn't make it the only video.
Move along, no sig to see here.