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RichardKennaway comments on Inhibition and the Mind - Less Wrong
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I don't believe this is the case. The higher levels operate by means of the lower, not instead of them. The lower processes show through on their own not when they are especially powerful, but when the higher processes are conflicted or absent.
In the case of the cortex vs. the limbic system, that is clearly not the case. The two inhibit each other - when one becomes active, the other's activity is reduced.
The layers are even approximately reflected in the brain's gross structure - the newer layers are usually stretched above and across the more primitive ones. This is especially clear when brains from different animals are compared.
The models of brain behavior taken from AI architectures - which is going in the wrong direction, but that's what some people do - would say that there is an ordered hierarchy of behaviors. That is, if behavior A sometimes inhibits behavior B, then behavior B never inhibits behavior A.
I think that's wrong for the brain in general. But I don't know if older layers can inhibit newer layers. Can they?
The answer is a resounding 'yes', at least in the sense that sufficient activation of the older parts retards the functioning of the newer.
People with sufficient limbic system activation (rage, disgust, sexual arousal, etc.) literally cannot think in a rational or sophisticated manner. Their ability to control and direct their behavior becomes impaired, and they tend to act impulsively.
Probably both. Adults don't normally show the grasping reflex at all. But certainly some actions are built from others.
It needn't look like the grasping reflex when in use by another system. I'm not familiar with the neurology, but if the grasping reflex that can appear in case of trauma is produced by the same system as in the baby (rather than being a chance similarity), then I'd bet money that that system is a functional component of the healthy adult, not a piece of scrap that is being suppressed.
Does anyone want to put up £100 against my £100? I've just googled it, and although I've seen the suppression hypothesis asserted in several places, I haven't found any investigation of the matter.
I think there's some confusion here about what I mean. I will attempt to clarify.
The grasping reflex only occurs when something foreign touches a baby's hand or foot, not when the baby touches itself. It requires the processing resources of the brain to distinguish between the two, which is why this reflex is not mediated by the peripheral nervous system.
As the baby ages, the reflex - by which I mean the action of grasping - dwindles and ceases. It no longer occurs.
The parts of the brain responsible for triggering the action still exist and are known to continue to function. However, their final result no longer occurs.
When sufficient frontal lobe damage takes place, the reflex appears again, which suggests that they either counter the signal from the reflex center or override it.
Seems like it would be hard to test. You looking for a long-term bet?
Bald assertion here
I think it will have to be long-term. I'll even make a more general hypothesis that this applies to all infant reflexes of all species: for any reflex that can reappear in the adult under abnormal circumstances, the system producing it is a functioning part of the healthy adult.
What are some examples of observations or conclusions that would lead to you winning this bet? Likewise losing.
Good question. A candidate for deciding the bet would arise if:
Someone investigates some infant reflex in some species, that reappears in the adult under reproducible abnormal circumstances.
They physically locate the mechanism producing it in both cases and demonstrate it to be the mechanism, and the same mechanism in each case, not just a chance mimicry.
They examine that mechanism in the healthy adult.
Then I lose if it is present but having no effect, which might be demonstrated by excising it.
I win if it is found to be a functional part of the nervous system with an identifiable function.
Bet to be decided by the first such candidate that comes to the betters' attention.