After writing several memristor models with SPICE last week, I decided to post a short tutorial here on the subject. I’ll concentrate on modeling the memristor introduced in the Nature Nanoletters’ article Memristive Switching mechanism for metal/oxide/metal nanodevices by Yang et al., published in July 2008. More specifically the model is an enhanced version of the one derived in the article CNN Using Memristors for Neighborhood Connections (IEEE CNNA 2010) by me and Mika Laiho. Read the rest of this entry »

Insightful people have noted that the brain has been difficult to understand from simple measurements because of its relative irreducibility to single neuron dynamics, suspected to be a result of emergent properties.  Line up a few hundred million transistors very carefully and you get a fast but ’stupid’ processor; bag a bunch of proteins with a lipid membrane and you’re still far from a functioning cell; the list goes on.  Something about the whole, goes the cliche, is greater than the sum of its parts.  I’ve traditionally only heard about this concept as it applies to neuroscience, but I recently came across a great quote from D’Arcy Thompson that could use some fresh air on the Internet.  In terms of cell biology, he warns against thinking of a multicellular organism in terms of its constituent cells, arguing instead that the biophysics is better understood in terms of the whole tissue and the interactions between its pieces.  I’m not sure whether or not this was added in the revised edition of On Growth and Form (1942), but I’d like to think that this was written in the first edition, published in 1917: Read the rest of this entry »

If you had doubts before starting to read Neurdon, I think that by now you have come to the realization that there are as many neuroscientists that use computers than computer scientists that want to “use” neuroscience. This post is another example of the latter: Steve Furber, Professor of Computer Engineering at the University of Manchester and leader of the team that designed the the 32bit ARM microprocessor, is trying to build a large-scale neural simulator out of ARM processors. Read the rest of this entry »

Note: This posting summarizes some arguments I presented at the 2010 IEEE Symposium on Circuits and Systems. The complete presentation is available at this link.

Much of the recent interest in HP’s finding the “missing” memristor has been based on the presumption that it is correctly interpreted as the “4^th fundamental circuit element” after the resistor, capacitor, and inductor. The original argument from Leon Chua was that there were four ways to link the variables of charge and current to the variables of flux-linkage and voltage. The resistor, capacitor, and inductor represent three ways to link these variables while the memristor was postulated as representing the “missing” link connecting charge and flux-linkage. This may seem like a reasonable argument at first glance but it is not without flaws. Read the rest of this entry »