MIT builds analog synapse chip

2011 Wikimedia commons (400px-Synapse_Illustration_unlabeled.svg)
2011 Wikimedia commons (400px-Synapse_Illustration_unlabeled.svg)

Recently MIT announced a new brain chip, a breakthrough device that simulates a single brain synapse with an analog chip.

We have discussed before the digital nueromorphic chip activity going on (see my IBM introducing their SyNAPSE chip and Electro-human interface posts). However both those were digital, this new MIT chip is analog.  The chip uses ~400 transistors and was fabricated using VLSI processing.

Analog, whats that?

Given that the world has gone digital, analog devices may be foreign to most of us.  But analog dominated the way electronics worked for the first half of last century and were still pretty prominent during the last half.

Nowadays, such devices are used primarily in signal processing, and where streams of data are transformed from one mode to another (serial/deserializers).   An analog signal has a theoretically an infinite resolution (Wikipedia), which should make it closer to real life and may be why some stereophiles perfer records to CDs.

Neurons are analog devices

That being said, it’s a treat to see some new analog technology come out that’s better than digital implementations.  One would have to say that neural activity is by definition analog and as such, should make simulating brain activity much easier.

The advantage of analog can be seen in that the neural synapse is the connection between two neurons.  Information is transferred between the two neurons by the take up of Ions.  In the case of the MIT synapse chip, the same sort of process occurs but in this case information flows based on gradients of electronic potential.

In testament to the capabilities of the new synapse chip they were able to resolve a long standing debate in neuro-biology. The question was on how long term potentation (LTP) and long term depression (LTD) which enhances or depresses the information transfer across the synapse was accomplished in real neurons.  Previously, it had been postulated that LTP and LTD would depend on two different mechanisms in real cells. But there was one theory that said with a specific type of receptor, both LTP and LTD could be performed in a single way.

MIT researchers were able to configure their synapse-chip to mimic that new receptor and were able to show how LTP and LTD could work with this single receptor in the brain.

Onto the brain

Of course a single synapse is not much considering the brain has 100B neurons each with many 100’s if not 1000’s of synapses. But it’s a start.

Naturally, considering its built out of transistors using CMOS technology, it should follow Moore’s law and after 18 months or so we should have a chip with two synapses on it. Another 40 or so doublings more (~60 years from now in 2071), if Moore’s law holds, we can have a brain-chip with 100B neurons and 100T synapses on it.

Of course, this being a prototype, I suppose with today’s fabrication capable of  creating 40M transistors/chip, we may already be able to simulate 100K synapses and 100 neurons. Which means we should have a brain’s level of neurons and synapses in 30 doublings or ~2056.

Analog is better than biological

The other nice thing about analog logic and transistors, is that information processing in the brain-chip should be orders of magnitude faster than the brain’s biological processing.  Which is probably even more frightening.

The IBM SyNAPSE chip mentioned earlier was an all digital creation and had two chip cores, one provided “learning synapses” and the other “programmable synapses”.  This was probably an attempt to mimic neural processing in digital logic.

The analog brain-chip that MIT has invented, has no such distinction, supplying all synapse functionality in 400 transistors.   Nonetheless, any accurate simulation of neural processes can help us to understand how to mimic it better. The fact that we have an analog simulation neural processes should help us improve the digital simulation to more closely match the brain.

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Not sure what we should call this chip, it’s certainly not neuromorphic, because it’s a real simulation of analog neural synapses not a digital approximation.  I would use synapse- chip but its already in use.  I kind of like the brain-chip but that may be stretching it a bit. Maybe the neuron-chip is best for now

Now that we know the date for the singularity, hopefully we can be ready to deal with whatever happens then.

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