Not Oscillations Traveling Waves


#1

Terry Sejnowski points out the brain does not oscillate it instead has waves that travel.

He also talks about a globally integrated workspace. @Bitking


#2

I have always thought of oscillations in this way. Is this a new way of thinking in neuroscience?


#3

I like the analogy that a stimulus is like dropping a pebble into a pond and the ripples is its history spreading outward. The interference pattern of waves is also interesting. Depending on the order in which the different stimulus arrives, the interference patterns differ. It is like the interference pattern is the signature of what happened in that period of time.

I’ve been wondering about these wave-like patterns since I Blue Brain Project released their videos a few years back. https://www.youtube.com/watch?v=3Fmsq_Qg7Nw&t=260s


#4

Thanks for the link. It was very helpful. I have been hoping for more news related to traveling waves, including simply made information containing spirals described towards the end of this opening post:

With so much new information coming in so fast I’m hoping to save time by not guessing where to next go with the episodic memory and instead do my best to keep up with all the developments that are making it easier to add more detail to the model.

My best to everyone. Keep up the good work!


#5

What I don’t understand is that it seems like there is loads of activation going on here. The level of activity in those waves goes against the idea that activity is sparse in the cortex. I did read somewhere that the lower layers are sparser than the higher layers which matches what I heard somewhere else that the frequency of activity is slower in the deeper layers.

Maybe these waves occur only in higher layers?


#6

Layer 6 is very sparse, but layer 5 is less sparse than L2/3. According to one study, layer 5 alone is sufficient and necessary for oscillations. I think it makes sense for oscillations to originate from a less sparse group of cells because that is more of a map level function or something like that, as opposed to processing sensory contents. So you don’t want much sparsity.

Source for layer 5 generating oscillations: Intrinsic oscillations of neocortex generated by layer 5 pyramidal neurons (Laurie R. Silva, Yael Amitai, and Barry W. Connors, 1990). Sorry, I can’t find a free version.


#7

What do you think the role of these oscillations are? Many believe they are used as attractor states for memory retrieval.


#8

Interesting, I’ve just read on wikipedia that ‘liquid’ in ‘liquid state machine’ is used as the analogy similar to what the speaker used to describe travelling waves.

The word liquid in the name comes from the analogy drawn to dropping a stone into a still body of water or other liquid. The falling stone will generate ripples in the liquid. The input (motion of the falling stone) has been converted into a spatio-temporal pattern of liquid displacement (ripples).

Interesting coincidence, or did the speaker draw that analogy from ML to neuroscience?


#9

I thin they all started with a pebble in a pond and went from there.


#10

I don’t know much about attractor states, so I don’t know if oscillations could be involved in memory retrieval.

I think oscillations are involved in coordinate transforms, and probably other things.

Interference between three oscillations with slightly different frequencies based on walking speed and direction has been proposed to contribute to forming grid cells. This is not proven but it makes sense, especially if walking speed is controlled by oscillation speed in the first place.

My current opinion is that L5 does not process sensory contents and is instead concerned with something like which cortical columns are receiving sensory input, the shape of that sensory input, attention, timing of sensory input (which was proposed by Jeff Hawkins), etc. I’m working on a hypothesis based on that for grid cell formation with propagating waves which solves some of my questions about layer 5.

Questions about L5

My hypothesis only suggests answers to some of these questions.

  1. Why does one L5 cell type have robust sensory responses with direct thalamic input (at least in some regions) and project up the hierarchy, suggesting a sensory role, but also supposedly acts as the only cortical motor output, suggesting a role in behavior?
  2. Why does it seem not driven by thalamus in some regions? Why does it supposedly mirror L2/3 as an output layer and why does it receive strong seemingly minicolumnar input from L2/3?
  3. Why does it have smaller short latency receptive fields and larger intracortically driven longer latency receptive fields?
  4. What is the role of burst firing, and does it even exist in normal function, or perhaps it exists in a less extreme form? Do L5 slender tufted cells really only fire much during behavior, and if so, why?
  5. Why are there contradictory results about the influence of the apical dendrite?
  6. Is there a third fundamental L5 pyramidal cell type and what is it like?
  7. Why are there contradictory results about the influence of input from a higher order thalamic nucleus, POm?

Generally, I think L5 processes details of how the sensory input begins, such as the sequence in which different parts of the fingertip make contact when poking a surface. Propagating waves are useful for detecting sensory onset dynamics because they occur at the level of the cortical sheet and are useful for precise timing.

Details of sensory input onset is another source of information besides the static sensory input after making contact with the object, but it is ignored by HTM.

Edit: Via another area, hippocampus can modulate walking speed. I’ve only read the abstract.
Theta oscillations regulate the speed of locomotion via a hippocampus to lateral septum pathway (Franziska Bender, Maria Gorbati, Marta Carus Cadavieco, Natalia Denisova, Xiaojie Gao, Constance Holman, Tatiana Korotkova, and Alexey Ponomarenko, 2015) https://www.nature.com/articles/ncomms9521