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fMRI Data Reveals How Many Parallel Processes Run In the Brain

Posted by Soulskill on from the still-won't-run-crysis dept.

New submitter xgeorgio writes: From MIT Technology Review: "The human brain carries out many tasks at the same time, but how many? Now fMRI data has revealed just how parallel gray matter is. ... Although the analysis is complex, the outcome is simple to state. Georgiou says independent component analysis reveals that about 50 independent processes are at work in human brains performing the complex visuo-motor tasks of indicating the presence of green and red boxes. However, the brain uses fewer processes when carrying out simple tasks, like visual recognition.

That's a fascinating result that has important implications for the way computer scientists should design chips intended to mimic human performance. It implies that parallelism in the brain does not occur on the level of individual neurons but on a much higher structural and functional level, and that there are about 50 of these. 'This means that, in theory, an artificial equivalent of a brain-like cognitive structure may not require a massively parallel architecture at the level of single neurons, but rather a properly designed set of limited processes that run in parallel on a much lower scale,' he concludes." Here's a link to the full paper: "Estimating the intrinsic dimension in fMRI space via dataset fractal analysis – Counting the `cpu cores' of the human brain."

13 of 91 comments (clear)

  1. Re:Next please by NotInHere · · Score: 4, Funny

    No the brain runs a very efficient version of systemd that has replaced ascii bash through a binary remote code execution system which is much more efficient and simple.

  2. analog computer by Spazmania · · Score: 5, Informative

    The brain is an analog computer. The notion of parallelism is fundamentally different for an analog computer... In a sense, every single neuron is operating independently and in parallel with the rest. Describing it in terms of parallel processing with digital CPUs makes no sense.

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    1. Re:analog computer by mikael · · Score: 2

      You have neurons, which are arranged into "cortical units". These in turn are arranged into wide striate layers (for increased resolution) and pyramids (for higher levels of cognition). With human vision, the neural pathways follow the topology of the retina.

      http://en.wikipedia.org/wiki/T...

      With human audio, the neural pathways follow the frequency of sound (http://en.wikipedia.org/wiki/Tonotopy)

      This research paper covers the evolution of the human brain when compared to reptiles and other mammals:

      http://people.sissa.it/~ale/an...

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    2. Re:analog computer by Spazmania · · Score: 2, Insightful

      You misunderstand the difference between a digital computer and an analog computer. Both are based on 1's and 0's, on and off.

      The digital computer is driven by a clock strobe. When the clock strobes, the whole set of circuits accepts and processes the next inputs. As a result, the circuit is stable at the end of each clock cycle.

      An analog computer has no clock. Inputs are processed as soon as they arrive. As a result, the circuit is never known to be in a stable state. It's continually in flux based on its inputs.

      "Parallel processing" describes a digital computer in which multiple programs advance with each cycle of the clock. There is no clock in an analog computer. Every single circuit acts independently as soon as its inputs change. Groups of circuits can be heavily interconnected or lightly interconnected but that interconnectedness is very poorly described by digital computer concepts like "parallel processing."

      If we ever build a true AI on a digital computer, it won't work anything like the human brain. The underlying hardware is just too different.

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    3. Re:analog computer by Anonymous Coward · · Score: 3, Interesting

      I think that the distinction you are trying to draw is not digital versus analogue. It is synchronous versus asynchronous circuit design.

      You can build asynchronous digital logic circuits using various self-timing mechanisms. You do not have to use clocked input buffers to synchronize tiers of logic gates, that is just a convention that makes reasoning about the system a lot easier. The design process is much more difficult, as you have to consider many more combinations of signal paths much as in typical analogue circuit design. You can still use thresholds at the gate level to implement digital logic functions, and you can form and react to pulse trains to do things like serial communication of bits without a clock signal. Things like the 8b10b encoding can ensure that the signal remains in a disciplined mode such that timing can be recovered.

      You can envision hybrid designs where more and more self-timed communication happens between ever shrinking domains of conventional synchronous logic. Eventually, the clocking in those domains might be entirely derived from the self-timed input links, and at that point you have what sounds to me like an asynchronous digital system.

    4. Re:analog computer by ultranova · · Score: 3, Insightful

      The brain is an analog computer. The notion of parallelism is fundamentally different for an analog computer...

      Citation needed. Intuitively the difference between a digital and analog computer is that the former has two discrete signal levels while the latter has a continuous band. This doesn't seem to imply anything about the actual structure of the system.

      Also, it isn't certain that the brain is actually analog. Individual neurons have discrete "firing" and "not firing" states. Firing rate is often summarized as neuron activation level, since it correlates with energy usage which is what various imaging techniques actually measure, but that doesn't prove that the timing of individual firing events doesn't matter. And if they do, we have a digital system.

      In a sense, every single neuron is operating independently and in parallel with the rest. Describing it in terms of parallel processing with digital CPUs makes no sense.

      Every single transistor is also operating independently and in parallel with the rest.

      --

      Forget magic. Any technology distinguishable from divine power is insufficiently advanced.

    5. Re:analog computer by tlhIngan · · Score: 2

      You misunderstand the difference between a digital computer and an analog computer. Both are based on 1's and 0's, on and off.

      The digital computer is driven by a clock strobe. When the clock strobes, the whole set of circuits accepts and processes the next inputs. As a result, the circuit is stable at the end of each clock cycle.

      An analog computer has no clock. Inputs are processed as soon as they arrive. As a result, the circuit is never known to be in a stable state. It's continually in flux based on its inputs.

      Actually, no.

      What you described are digital computers, one is a traditionally clocked system, while the other is asynchronous (clock-free) system.

      An analog computer doesn't use 0s and 1s to compute, but a scale of voltages. Inside it are a bunch of amplifiers (typically operational amplifiers, the term "operational" is important) which calculate.

      An op-amp is called that because its properties are such that it can be adapted to perform calculations - common op-amp circuits include the adder (summer), buffer, inverting amplifier (multiply by -1, combine with adder to make subtractor), integrator, differentiator, multiplier/divider (non-inverting amplifier), etc.

      Combine these and you'll end up with something that takes input, processes it, and produces output, something a traditional model of a computer does. Now, it's relatively fixed-function in that it's not easily programmable without rewiring it, but early computers WERE analog. Back when digital computers took up rooms, analog computers were plentiful - often as bomb sights and targeting computers in ships and aircraft, and early electronic ignitions for engines were also the same.

      And they were often simpler to understand and had fewer parts than their digital counterparts. Of course, digital wins in the end because the ease of programmability means the extra complexity is justified - changing something in an analog computer can mandate rewiring the entire thing, while on a digital one it's change, rebuild, deploy.

  3. Ill go further Process is a bad term here by Crashmarik · · Score: 2

    It has no relationship the common usage of the term in computing, a far better way of phrasing that would be tasks.

  4. If you're a man... by Hognoxious · · Score: 4, Funny

    ... the answer is one.

    --
    Confucius say, "Find worm in apple - bad. Find half a worm - worse."
    1. Re:If you're a man... by Guppy · · Score: 2

      ... the answer is one.

      No, no. Definitely capable of at least two threads, since when I get a boner my brain still manages to spare processing power to continue breathing. Although if I were to try chewing gum at the same time, there could be trouble.

  5. Re:Oh Please Edge Detection and Motion Detection by timeOday · · Score: 2
    Oh, darn, you beat me to it.

    But I just wanted to add that fMRI lacks the resolution to measure individual neurons, so I don't know how it could possibly be used to rule out neuron-level parallelism. It is like recording people's height in whole feet and concluding there are only 6 different heights of people.

  6. Re:analog computer AND nonlinear by fygment · · Score: 2

    Mod parent up AND consider:

    a) remember that the use of Independent Component Analysis (ICA) is appropriate for linear processes and therefore must necessarily be, to an unknown degree (until you actually know the underlying distribution), an approximation ie. the more unlinear the process, the less ICA accurately reflects the underlying processes; and

    b) the actual processing methodology of the brain is unknown, heck, we do not even understand the encoding used by the brain.

    So the article really rests on the assumption that the brain is composed of linear processes operating like a modern digital computer.

    Ummm ... no.

    --
    "Consensus" in science is _always_ a political construct.
  7. Phrenology? by Culture20 · · Score: 2

    How does this apply to phrenology?