- #246
apeiron
Gold Member
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Lievo said:That we never expected... strawman but interesting: at a glance I would say default mode, cognition in cerebellum, consciousness in insula, modulation of cortical tickness, BCI with person supposely in coma.
OK, you suggest five neuroimaging breakthroughs. Let's see if they involve the discovery of top-down principles.
1) Default mode network
Yes. Raichle/Snyder contrast the bottom up "driven" view of computer science and the top-down systems view now revealed.
One view posits that the brain is primarily reflexive, driven by the
momentary demands of the environment. The other view is that the
brain's operations are mainly intrinsic involving the maintenance
of information for interpreting, responding to and even predicting
environmental demands.
http://www.appliedneuroscience.com/Default%20mode-a%20brief%20history.pdf
Then Friston/Carhart-Harris have more explicitly linked the default mode to the top-down Bayesian brain model in http://brain.oxfordjournals.org/content/133/4/1265.full.pdf+html
Some interesting snippets in that like...
Furthermore, we associate failures of top-down control with non-ordinary
states of consciousness, such as early and acute psychosis, the
temporal-lobe aura, dreaming and hallucinogenic drug states.
2) Cerebellum plays role in cognition and behaviour.
Again yes. I well remember the shock that the Fox/Raichle paper created (a PET experiment BTW, not that that matters).
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC391365/
It did indeed show that language production was not confined to a couple of brain modules but was a dynamical hierarchy that included even "low level" structures like the cerebellum. For a long time critics insisted it must be an artifact.
So again a significant experiment because it undercut the reductionist computational model of brain processing and pointed to a hierarchical view of top-down in interaction with bottom-up. That was precisely why it got people excited. I was at conferences where the work was presented (as well as discussing it with Raichle, Fox, Posner and others).
3) Consciousness in insula
I presume you mean Craig's recent hypothesis - http://www.appliedneuroscience.com/Insula-what%20you%20feel%20&%20consciousness.pdf
Sadly you would be right that he wants to call it the seat of consciousness. So not a systems point of view. But then dig into the actual research and this claim starts to evaporate like the attention grabbing hype it is.
Quite quickly we are back into a standard hierarchical view of brain function. Craig says the insular handles the high level view of the interior millieu while the cingulate does the job for motor intentions. They work as a team and both have spindle cells (for strong and fast top-down control over the respective hierarchies below them). Etc. The seat of consciousness fast becomes the hierarchical systems story that it should be.
So disregard the hype and the insular cortex is not especially significant except as a higher brain area that is important for top-down influences.
4) Modulation of cortical thickness
Not sure what you mean here unless you are talking about the anatomical studies of brain maturation?
If so, isn't it interesting that the most top-down areas develop the slowest. As a hierarchy it takes time to develop from the bottom up (construction) and for the global constraints to fully organise. Exactly as hierarchy theory would predict (see Salthe on the stages of immaturity, maturity and senescence).
Adolescents are now said to be impulsive and temperamental simply because they are incapable of top-down regulation of their behaviour. The brain areas have not fully developed.
So if this was the neuroimaging finding you meant, yes it was big news. And because it was all about top-downness in neuroscience.
5) BCI with person supposely in coma
OK, again top down (if you are talking about brain computer interfaces and locked in syndrome) - if indirectly this time. A loss of top-down control in coma patients means they can't overtly produce response. But can generate enough EEG activity to be translated as an attempt to command. So a demonstration of top-down control over computer hardware.
I'm puzzled how this counts at a great breakthrough for fMRI though. Perhaps you can elaborate.
Anyway, five findings and the actually significant ones (that is 1, 2 and 4) are significant because they confirmed that the hierarchical approach to the brain, with top-down effects being key, are the way to go.