According to the BBC, a processor is the brain of a computer, but it seems that the hardware has neuroscientists baffled.
A paper published in PLOS Computational Biology wondered if more information is the same thing as more understanding. Eric Jonas of the University of California, Berkeley, and Konrad Kording of Northwestern University, in Chicago, who both have backgrounds in neuroscience and electronic engineering, reasoned that a computer was a good way to test the analytical toolkit used by modern neuroscience. However they had to admit that they were wrong.
They took an MOS Technology 6502 chip which was first produced in 1975 and famous for powering, among other things, early Atari, Apple and Commodore computers. It has 3,510 transistors and is simple enough to create simulation that can model the electrical state of every transistor, and the voltage on every one of the thousands of wires connecting those transistors to each other, as the virtual chip runs a particular program.
The simulation produces about 1.5 gigabytes of data a second—a large amount, but well within the capabilities of the algorithms currently employed to probe the mysteries of biological brains.
But brain science and electronic science started to diverge in the test. For example if you damage part of the brain you know what is going to be stuffed up. A chip though comes up with false positives.
Disabling one particular group of transistors prevented the chip from running the boot-up sequence of “Donkey Kong but allowed it to run other games.
If it were a brain you would think that transistors were thus uniquely responsible for “Donkey Kong” but the reality is that it is just part of a circuit which implements a much more basic computing function that is crucial for loading one piece of software, but not some others.
The bofins looked for correlations between the activity of groups of nerve cells and a particular behavior but when they tried to apply this to the chip, the researchers’ algorithms found five transistors whose activity was strongly correlated with the brightness of the most recently displayed pixel on the screen.
Jonas and Kording know that these transistors are not directly involved in drawing pictures on the screen and they are only involved in the trivial sense that they are used by some part of the program which is ultimately deciding what goes on the screen.
Jonas said that neuroscience techniques failed to find many chip structures that the researchers knew were there, and which are vital for comprehending what is actually going on in it.
In fact, all the neuroscientists’ algorithms could detect in the chip was the master clock signal, which co-ordinates the operations of different parts of the chip.
In short, computers and brains have got as much in common as a packet of crisps has with the Empire State Building. This means that the BBC will have to find a new simile.