Friday, January 04, 2013

Those great big lobes

The Master and His Emissary

Other posts in this series:

The malleableness of things   Dec18/12  
Two brain halves, disappearing bridge Dec 21/12  
Mind: the brain's experience of itself Dec 22/12  
Asymmetry of brain sides: size, structure, neurochemistry Dec 31/12

"Every individual mind is a process of interaction with whatever it is that exists apart from ourselves according to its own private history." - p.20.

How can you tell I'm practically paralyzed by this book? Here I am, catching myself back on page 20. It's for good reason though - I want to remind myself of some anatomy McGilchrist discusses there, and some definitive pondering he does on its implications. 

The frontal lobes are the "most lately evolved part of the brain" - I guess when he uses the term "brain" in this section, he means the vertebtrate brain. 

"Whereas the frontal lobes represent about 7% of the total brain volume of a relatively intelligent animal such as the dog, and take up about 17% of the brain in lesser apes, they represent as much as 35% of the human's much the same with the great apes, but the difference between our frontal lobes and those of the great apes lies in the proportion of white matter. (Semendeferi, Lu, Schenker et al 2002; Schoenemann, Sheehan & Glotzer 2005). White matter looks white because of the sheath of myelin, a phospholipid layer in which some neurones surround the axons, the long processes of the nerve cell whereby outgoing messages are communicated.  This myelin sheath greatly speeds transmission: the implication of the larger amount in human frontal lobes is that the regions are more profusely interconnected in humans. Incidentally, there's also more white matter in the human right hemisphere than in the left, a point I will return to (Allen, Damasio, Grabowski et al 2003)."

He thinks these great big white, densely intraconnected lobes enable us to "stand back from the world, from our selves, and from the immediacy of our experience", "plan, to think flexibly and inventively", "take control of the world around us rather than simply respond to it passively", gain distance from the world, "rise above" it. 

He describes immediate bodily experience as "the actual terrain in which we live", "where our engagement with the world takes place alongside our fellow human beings", and remarks, "we need to inhabit it fully." He likens this to living along a "horizontal axis." All animals do this.

Even so, "we need to rise above the landscape in which we move, so that we can see what one might call the territory." This is like a vertical axis, something other animals can't do. It gives us "an optimal degree of separation between ourselves and the world we perceive", "necessary distance", helps us understand it. Provides an optimal focal length. 

"Distance can yield detachment, as when we coldly calculate how to outwit our opponent, by imagining what he believes will be our next move. It enables us to exploit and use. But what is less often remarked is that, in total contrast, it also has the opposite effect. By standing back from the animal immediacy of our experience we are able to be more empathic with others, who we come to see, for the first time, as beings like ourselves." 


1. K. Semendeferi, A. Lu, N. Schenker, and H. Damasio; Humans and great apes share a
large frontal cortex. nature neuroscience •  volume 5  no 3  •  march 2002 p 272-6 [full access pdf]

2. Schoenemann PT, Sheehan MJ & Glotzer LD; Prefrontal white matter volume is disproportionately larger in humans than in other primatesNature Neuroscience 8, 242 - 252 (2005) 

3. Allen JS, Damasio H, Grabowski TJ, Bruss J, Zhang W; Sexual dimorphism and asymmetries in the gray–white composition of the human cerebrumNeuroImage Volume 18, Issue 4, April 2003, Pages 880–894

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