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Sabbath School for a New Generation

Among Seventh Day Adventists, Sabbath School is a time for discussion and learning. It is the belief of this site that Sabbath School should be an exciting venue for the discussion of new ideas, instead of rehashing old arguments. So welcome to a virtual Sabbath School, a Sabbath School for a new generation.

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I am an Electrical Engineer, working at Intel in the Portland area. I received my undergraduate degree from Walla Walla College and graduate degrees from the University of Southern California. The views expressed on this website are my own and do not reflect the viewpoints of anybody else. I reserve the right to change my mind at any point in time.

Monday, March 27, 2006

Cool brain fact

Have you ever heard that we only use 10% of our brains? It turns out that it is a myth. However, I ran into a little factoid from Carl Zimmer. He researched a claim that he found in a press release about a bioengineer at Stanford.

According to Boahen, the brain is capable of performing 10 quadrillion (that's 10 to the 16th) "calculations," or synaptic events, per second using only 10 watts of power. At this rate, he says, a computer as powerful as the human brain would require 1 gigawatt of power.

My laptop runs at about 60 Watts and isn't nearly as powerful as the human brain. The speech recognition software on my computer can barely keep up with my speech. But it is only translating the speech signal into text. The computer has no understanding of what all those words mean. Yet my brain can recognize what somebody is saying and understand the meaning while regulating my breathing, making sure I keep my balance, identify interesting objects in the room, contemplate what I am going to cook for dinner, etc...

Carl Zimmer researched the 10 watt claim and it turns out that while this is a low figure, it is within the ballpark. According to the Neuroscientist that he talked to the figure is closer to 15 watts. Still less than a lightbulb. Now of course the other claim has to do with the number of calculations, which was addressed in the comments by Harlan.
Also, it's really a mistake to equate synaptic events with calculations in a computer. Synaptic events are much, much simpler. When computer scientists talk about a "calculation", they usually mean an amount of computation that takes one clock cycle, which might be to add two long numbers, or decide if one number is bigger or smaller than 0. To the extent we understand what computations synapses compute, they're probably, at least mostly, small portions of an addition. The simplest model of a neuron basically computes "if the sum of the average firing rate of my input neurons is more than X, fire". Any single synaptic event affecting that neuron is likely to be one of probably thousands of such events that is involved in that computation...

But that doesn't take away from the fact that our brains are truely amazing organs. A modern desktop can perform several billion operations per second (10 to the 9). And if it takes a thousand synaptic events to equal one floating point operation, then our brain is still over a 1000 times more powerful than the top of the line desktop.


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