HTM Cheat Sheet



@rhyolight Could you please have a look at my last edit to the original post to confirm that I didn’t add any incorrect or misleading info? I added a section dedicated to SDRs and the spatial pooler. I also re-ordered a little bit the sections: in particular, I moved the section dedicated to neurons to the top, as I think it’s more basic and fundamental than other ideas (e.g. minicolumns). Later, I’ll probably complete the section on the SP and TM. Part of the info I added is based on the HTM School videos you created and the BAMI book.


This wiki is a great reference. Thanks!

Two topics I found in On Intelligence that I’m not sure are addressed here:

  • chapter 6 page 87 “Figure 1 represents the first four visual regions involved in the recognition of objects (…). Biologists label them V1, V2, V4, and IT.
    Jeff Hawkins discusses at length that information travels up and down a hierarchy over several layers. These are not the 6 (or 9: 1, 2, 3a, 3b, …) layers within the 2,5mm neocortical sheet, but 4 sheets that work in a hierarchy to ‘understand’ the (in this case visual) information.
    It would be interesting to know why biologists call them V1, V2, V4 and IT. Why not V1, V2, V3 and V4? What does the IT stand for and why the exponential (?) numbering.
    Also, do other sensorial regions have four layers? Do some have less or more, and do we know how this number 4 has been established? Is it somehow an ideal number of layers for an hierarchy?

  • chapter 8 page 152: “Let’s say the cortex has 32 trillion synapses. If we represented each synapse using only two bits (giving us four possible values per synapse) …
    32 trillion synapses is a rough estimate, I get that, but how do I have to interpret the 2 bits per synapse? Is that the weight of the connection?


Working out the naming of brain regions has been an annoying issue for me. Each researcher seems to feel the need to name everything from scratch.

As far as just the V1 through V6, wiki has a nice entry on this:

One of the confounding factors on the visual cortex is that it splits up into the WHAT and WHERE streams and these two pathways do not exactly match in terms of both location and connectivity.

I did a write-up on this topic earlier which prolly goes into this in more depth than you were looking for here:

As far as the 2 bits per synapse question; I an not sure what Jeff was trying to convey so I will pass on answering that.