MacLean's Triune Brain Nonsense? Options

[Unknown]

Is MacLean's Triune Brain concept utter nonsense with no basis in neuroscience? I'm inclined to think it is, and have been told as much from many neuroscientists. Yet, the triune brain concept remains popular with laymen and the general public. Why is this? Here's an excerpt from a pro-MacLean site over his Triune Brain theory, to give you an idea of what his theory is all about.

[rhymer]

I hadn't realised Mclean was the source of this theory, which seems sensible to me from my own experiences.
I don't really bother whether there are three brains as separate entities, considering them myself as three 'layers' of development. Each has specialised functions for survival which may or may not be superceded by higher levels.
It seems to fit in with evolutionary ideas, and the way different groups of functions disappear as a brain nears death [ie., an ascendency of functions which decays in order of complexity].

What alternative theories exist?

[Unknown]

[Paul King]

[Rick]

Perhaps if we think we understand the brain we have over-simplified it. We should also note that the older brain portions have kept evolving right along with the growth of the neocortex. Today's reptilian brain may be much more capable than the brains of reptiles that lived 300 million years ago.

[Hey Hey]

[Rick]

The crocodilians have had similar body form for 300 million years. It would be interesting to see brain size per body weight graphed as a function of time.

[Hey Hey]

[rhymer]

There is a lot of possibly relevant (at least related) info here

http://www.bbsonline.org/Preprints/OldArch...bbs.finlay.html

[Unknown]

[Hey Hey]

[Paul King]

[Enki]

Oho!

[Unknown]

Hi Enki,

are these the three layers?

Obsolete.
Hopeful.
Over-the-top.

Hence Oho?

[Enki]

Hi Unknown,

Oho means oho my dear.

Bests,
Enki

[rhymer]

Thanks Enki, but I must admit, I thought that was what Father Christmas said?

[Enki]

[Unknown]

[avisolo]

Read what Maclean himself said about it here:
http://www.d.umn.edu/~rlloyd/EducatorsInstitute/Mac2.htm

[Unknown]

[Paul King]

Read what Maclean himself said about it here:
http://www.d.umn.edu/~rlloyd/EducatorsInstitute/Mac2.htm

It's a good link and makes for an interesting read but I still think Maclean's triune brain concept is childishly naive and explains nothing. Anyone sufficiently appreciative of the brain 's organization and complexity will tell you the same thing.

The value of the triune brain concept is as a point of view, not as an explanation of mechanism. It is a systemic way of thinking about the cause of behavior that is an improvement over Freud but still a long way from what is "really" going on.

The strength of the idea (the intuition, really), is that most instinctual behaviors (what he calls ancestral memories selected by evolution) are encoded in the circuits and pathways of the limbic system and below. Conversely, most cognitive functioning, acquired memories and skills are encoded in the cerebral cortex.

Current theories still support this basic separation, however the models have come a long way since MacLean's time. The neocortex, for example, is not at all separate and independent from the older parts of the brain. MacLean did not say that it was, but he did seem to talk about it that way. What MacLean really said was that the limbic system is a fairly self-contained, tightly interconnected system, and current theories would not contradict that.

Today's explanations of brain mechanism focus much more on statistical learning models and pattern classification. The current models around emotion tend to map the phenomena people associate with emotions onto reinforcement learning and behavior strategy selection paradigms. The trend these days seems to be not so much in understanding instinctual wiring, but in understanding learned behaviors. Learned behaviors are often the interaction of certain neural pathways and circuits (which could be called instinctual) with structured adaptive processes that lead to the formation of optimal behavior.

Emotions are being understood these days in terms of neurotransmitter systems and their relationship to behavior strategy optimization processes, for example, the study of "neuroeconomics" and neural mechanisms of decision making, risk assessment, and exploratory learning.

[lucid_dream]

Paul MacLean should have recanted his utterly ridiculous Triune Brain Theory decades ago.

It's amazing that you still find blatantly false theories of the brain floating around! MacLean's theory is right alongside Aristotle's notion of the brain as a cooling system.

[TaylorS]

IMO the Triune Brain hypothesis is at most, a profound oversimplification. Our brain stem, cerebellum, and mid-brain are not unchanged relics, they have evolved right along with the cerebrum, it's just not as obvious because evolution tends to be conservative and economical, you don't need to create new structures if you can just "reprogram" structures already there for new purposes. The cerebellum, especially, does not get the respect it deserves; it's not only important in coordinating movement, but is also plays a role in coordinating our thought patterns. Certain parts of the thalamus are vital in maintaining a state of conscious awareness, damage to those regions will turn you into a vegetable.

[Robert B. Mounts]

Let's examine the question from a different point of view.

Humans certainly respond to stimuli in different set patterns 'as though' three different operating systems were at work.

'R-complex' may not refer to a specific structure that emulates a rattler. But the reactive behavior patterns of 'see-strike' make a great deal of trouble for human beings, and many, perhaps most, people experience them (to their own amazement and dismay.)

Simple observation leads us to the conclusion that people are/act like mammals a good part of the time -- nurturing young, organizing as groups or packs, often around an alpha male, even coordinating tasks and attacks as a unified society. (Do most mammals, then, 'communicate'?)

And cerebral behavior -- "before you do, think it through" -- is the pride of our species, though a lot more often discussed and prescribed than undertaken.

These response patterns seem to occur at different times, under different conditions, in the same individual, so that others with with whom the respondent interacts later would think they had met an entirely different person.

So perhaps the 'triune brain' theory, as Carl Sagan presented it, is only a catchy, back-formed metaphor that essentially represents a widely recognized psychological pattern?

[dtubin]

Let's examine the question from a different point of view.

I couldn't agree more. If we leave alone physiological side which everyone seemed to struggle with.. It seems perfectly consistent with behavioral human model.

[Flex]

IMO the only thing of importance to take away from all of that is that, "it had previously been assumed that the highest level of the brain, the neocortex, dominates the other, lower levels. MacLean has shown that this is not the case, and that the physically lower limbic system, which rules emotions, can hijack the higher mental functions when it needs to."

If you want answers, don't look to science. At best you will get a theory. Things cannot be proven, only disproven. I believe one ought to take their daily dose of scientific papers with a grain of salt, in the understanding that 50 years down the road the entire picture will be different. We can model molecules with ball and stick models that do not represent reality in anyway, yet it is a very useful tool, just as this model has been useful. Doesn't mean it is correct

[Jakare]

If we are going to split the brain appart we should say there are 5 two 7 different brains depending upon if we want to think of the limbic system as divided in hemispheres or not like the neocortex is and counting the cerebellum aswell. The cerebellum itself is a really complex structure and is divided in two aswell.

But the more relevant division between brain structures is right and left hemispheres IMO hands down. The studies about corpus callosotomy are deeply amazing about how differently those two little fellas inside us can have a very different point of view.
http://www.intropsych.com/ch02_human_nervo..._operation.html