Not Oscillations Traveling Waves


#21

Bitking I have to say that nice paper sure got my attention! This video even shows vector pointers similar to the (instead upstream) yellow wave direction pointers shown in the upper right corner of the ID Lab 6.1:

I have been hoping that there would be a breakthrough like this. The abundant traveling wave action is exactly what I expected.

I’m still confident that HTM theory will work for temporal related learning that must occur at each place in the cortical map these (moving straw that locations in turn look through?) traveling waves travel across. Simplest way I can think of to proceed is add a visual cortex network that maps to retina locations where associated detectors start a wave in a given direction. I’m not sure what else would be needed to convert that information to places in space the navigation network requires but simple wave generating components would be there, and then need something like HTM theory to make a simple virtual critter come to life.

Your news was well timed. For me this winter became a dinosaur tracksite experiment marathon. The work is now mostly over due to spring weather making it too warm for (as in how road potholes are made) freeze-thaw cycle fracking to a depth of a foot or two, of a mostly above ground 20x40 foot block of bedrock. Work is planned for this summer in material with paper thin layers that are otherwise impossible to separate. Somewhere in them is at least one scientifically valuable layer needed by researchers who study here, but the scraps they saw came from an already weather worn area where we were lucky to find what we did.

I sense that neuroscience is finally close to discovering the fundamental principles of how our mind/body works. The need to include traveling waves and a predictive learning mechanism again for us makes the challenge much the same as successfully hybridizing HTM and the wave system I have been experimenting with.

Do you plan on trying to model these waves? Anyone?


#22

Gary,

I have this old post that discusses the possible origin of these waves. It is my suspicion that these arise in the thalamus and are injected into the cortex in L4. See the post for references and more detail:

You mention a larger model and I agree that HTM fits in this framework. I have outlined what I think that framework is here:


#23

Some oscillations are sent from higher order thalamus to primary cortex in L2/3 or possibly L5a (slender tufted cells). I don’t know if they are relevant to what you are talking about.

Unique properties of high-order thalamic inputs versus cortical inputs to primary somatosensory cortex

Summary

In L2/3 pyramidal cells of barrel cortex, POm (higher order thalamus) triggers a fast depolarization (e.g. 75 ms) then inhibition then a depolarization lasting ~750 ms. The long depolarization has oscillations at 10-20 hz and occurs for the weakest stimulation of POm which triggers the fast depolarization.

The authors say the frequency is similar to sleep spindles, which are generated by interactions between thalamocortical cells and thalamic reticular nucleus cells. The depolarization is small but pushed 6x more cells over firing threshold during sensory responses. I think that probably involves disinhibition of apical dendrites (see the next article) so the depolarization is probably not so small, just in a separate compartment than the soma.

Based on their discussion, it seems like an attention signal.

The repetitive/long lasting input from POm seems to allow LTP of input from L4 to L2/3 without L2/3 cells firing.

Higher-Order Thalamocortical Inputs Gate Synaptic Long-Term Potentiation via Disinhibition
The final version has a paywall, but not the preprint.

Summary

Rhythmic whisker stimulation or rhythmic paired L4 + POm stimulation (8 hz) causes LTP of input from L4 to L2/3, but not of input from POm to L2/3. LTP occurs without the postsynaptic cell firing.

This plasticity requires POm to activate NMDARs on distal apical dendrites of L2/3 cells and it requires POm to activate VIP+ interneurons, which inhibit somatostatin+ interneurons, overall disinhibiting those distal apical dendrites.


#24

There are multiple frequencies in the cortex that seem to be doing different things.
The alpha rate seems to be the rate that L2/3 uses to communicate between maps and the L2/3 & L4 layers have to work together to come up with an agreement on what to send.
L2/3 may be working at a much higher rate (gamma) to do local voting on hex-grid formation. (or macro-column voting if that is your thing)
I don’t recall seeing any oscillator circuits in the cortex but the lower and mid-brain is full of then. Having the thalamus gate those into the correct parts of cortex as needed seems plausible.


#25

I recall your earlier thoughts and was not sure whether reproducing what the paper and videos show was a problem on your end, of the cortical sheet. Excellent!

My interests have been so way at the tip of the other end (where there is no longer the uniform 6 layer structure and ultimately connects to motors) I could only hope the paper was good news for you and others too.

I’m also excited by the greater than expected progress of this project:

I was expecting this level to be reached in another year or so. If this progress keeps up then by the end of this summer the only thing I might only need to add is a moving invisible shock zone arena environment and plug the critters rudimentary brain into that. Well done!


#26

I have to wnder if there is a path from the lower brain structures, through th ethalamus, to the cortex.
I have noticed that there are patterns very similar to the overall cortex structure as shown in the clips above.
For example:

Also found here if you tube is blocked for you:

Following up on this loose end: where does this smell pattern end up in the cortex?