A ubiquitous spectrolaminar motif of local field potential power across the primate cortex [video]
Date Posted:
January 18, 2024
Date Recorded:
January 18, 2024
CBMM Speaker(s):
Diego Mendoza-Halliday Speaker(s):
Alex Major
All Captioned Videos Publication Releases
Description:
MIT scientists Diego Mendoza-Halliday and Alex Major discuss their most recent publication in Nature Neuroscience on the corresponding neuronal activity patters that exist across the cortex in primates and more.
[AUDIO LOGO] DIEGO MENDOZA-HALLIDAY: One of the most fascinating things about the brain is that despite looking like a mass of gelatin, it is really organized-- nicely organized-- into a beautiful structure. If you take the outer part of the brain, which is called the cortex, and flatten it out, you'll see that it is actually nicely layered like a lasagna but made of neurons.
That six-layer pattern is in fact present not only across the entire cortex in our brain, but also present in every single mammal on Earth, from dolphins to elephants to bats. And this is really an indication that this six-layer pattern is fundamental to the function of the cortex. But to understand that function, we really need to understand what neurons in different layers are doing. And the challenge there is that neuroscientists so far have failed to find a pattern of neuronal activity that corresponds to those six layers and is preserved across all areas of the cortex and all mammals.
ALEX MAJOR: Previous work from Andre Bastos and the Miller Lab showed that different layers and different frequencies have specific mechanisms in cognitive activity. So more and more researchers across the global routing at all layers of the brain at once. And what's really important is knowing what layer you're actually recording in and a way to discern what's the upper layers, what's the lower layers.
DIEGO MENDOZA-HALLIDAY: Andrew Bastos at the Miller Lab had previously observed a beautiful pattern of oscillatory activity across layers that we later called the spectrolaminar pattern. And in simple terms, this pattern is composed of high-frequency oscillatory activity that we call gamma in superficial layers and lower-frequency oscillatory activity in deeper layers.
ALEX MAJOR: It's actually a really simple formula. It's surprising no one's found it already. You take the raw signal, look at the power spectrum, and then perform a really easy normalization across channels. It's one line of code. You can create this relative power spectrum. And it creates this pattern that looks kind of like a check mark.
DIEGO MENDOZA-HALLIDAY: Andrews Bastos, now a professor at Vanderbilt, was recording from some regions of the cortex. I was recording from other regions. And so we decided to join forces and ask the question, could we find that spectrolaminar pattern in all of these regions and perhaps across the entire cortex? And what we found by the end of the study is that the spectrolaminar pattern was present in as much as 14 areas of the cortex across the entire cortex.
And so this was the first time that a pattern of neuronal activity across layers was observed all across the cortex, just like the anatomical layers. So this was really exciting. This was an indication that the pattern we were describing represented a fundamental property across all cortex. But the ultimate demonstration that this pattern was truly ubiquitous came when we were able to show that the pattern was actually present across different species, including humans.
ALEX MAJOR: So we can take this new pattern of brain activity. And when we line it up to the anatomy, we found it matched really well with individual anatomical cortical layers. Normally, you have all layers data lumped together. You don't know what's upper layers. You don't know what's deeper layers. With this new pattern, we can map it onto the physiology and say, OK, now this part of the data is from the upper layers. This is from the deeper layers. And this is important because we know they perform different functions.
Not only did this pattern allow us to identify the different layers and discriminate, but it worked better than the historical pattern known as current source density sync. And not only that, this pattern works in all brain areas, not just the visual cortex.
DIEGO MENDOZA-HALLIDAY: Being fully automated, this method will now standardize localization of cortical layers across studies and allow comparisons of results across these studies. We hope this will lead to more studies examining neuronal activity in the framework of cortical layers and eventually to a better collective understanding of the roles of these layers in brain function.
ALEX MAJOR: So this pattern could be really useful for electrode implantation. If we have the cortical layers here and this is the electrodes recording window, we can see in real time whether or not the electrode is covering all anatomical layers or not. So this is useful not only for research but also for human neurosurgery one day.
DIEGO MENDOZA-HALLIDAY: Our results suggest that this laminar pattern of oscillatory activity represents a multi-purpose mechanism that can help perform computations in different cortical areas to carry out the variety of functions of the cortex from hearing to working memory to motor planning and so on. They also suggest that these mechanisms work similarly across mammals, including humans. But we also saw differences in the spectrolaminar pattern between species.
And this suggests that the mechanisms may have evolved and perhaps even refined themselves through evolution. And this perhaps may help us explain why humans have higher cognitive abilities than other animals.
[AUDIO LOGO]
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