Chapter 10: What's in a Species?

• Introduction
• It is unusual to have only one species from an evolutionary group
• Times when there are multiple hominid species: 50 to 100 thousand years.
• Total time that hominids have been around: 1 million years.
• Definitions
• The homo genus is controversial
• Some say that Neanderthals, etc. should be in that genus.
• Some say that Boskops were a separate species.
• Fallacies of the notion of race
• Separate gene pools vs. interbreeding populations.
• Not strict categories
• Eugenics programs
• Have occurred throughout history
• Part of the problem is how do you define "better"
• Surprising list of people who have supported such movements
• Winston Churchill - sterilizing the "feeble minded"
• Alexander Graham Bell - sterilizing the congenitally deaf
• George Bernard Shaw - involved in the eugenics movement
• Races Versus Gene Pools
• Genetic variation in a subgroup is just as common as in the entire population
• May be restricted in what can vary.
• The absolute amount of variation is the same.
  

Notes on Chapter 9: From Brain Differences to Individual Differences

The mail takeaway I got from this chapter was that genes are an important aspect of a person's potential, but they only determine about half of the traits a person might have.  The rest are determined by the "environment."  "Environment" in this case can mean things as diverse as diet, training, interaction with microbes, etc.


The authors seemed to be careful to point out the limits of genetics and the problems with trying to define just what a "superior" person is.  Three examples are given of people who can be seen as handicapped in some way, and yet possessing significant advantages in another way.

The authors describe the results of studies using fMRIs and reading skills which indicate a correlation between reading and certain brain configurations.  The problem is that having two related traits does not tell you whether one trait causes the other or if they are both related to some other trait. 
For example: do people with good reading skills cause their brain to be configured a different way, or does having a particular configuration mean that the person is a good reader?  Another possibility could be that people with good reading skills receive abundant dietary essential fatty acids during a key period of growth.

Diffusion Tensor Imaging

According to an article I found, Diffusion Tensor Imaging (DTI) reveals the circuits in the brain that are activated during a given activity.   DTI is another form Magnetic Resonance Imaging (MRI) that tracks the large movements of water molecules.  Since blood is largely water, this sort of scan should show the routes that blood is flowing to and hence show the neural pathways that are being activated.

Contrast this with Functional MRI, which shows where carbohydrates (sugar) is being consumed in the brain.

Chapter 9: From Brain Differences to Individual Differences

• Introduction
• Do genetics predispose individuals to have different abilities
• Examples of people with different brains/abilities
• Les
• Premature, blind, only expected to live a short time
• Incredible memory, natural concert pianist
• Willa
• Williams Syndrome
• Brain is 15% smaller than average
• At 18, roughly the level of a first grader
• Gifted writer
• Kim
• Missing corpu collasum and anterior commissure
• Can perfectly recall anything he has read
• Similar to the "rain man" in terms of difficulties with day to day life.
• Very minor genetic changes resulted in these differences
• What sorts of changes could bring about these changes?
• Brain Paths
• Diffusion Tensor Imaging (DTI) 
• MRI that traces paths through the brain
• May lead to predispositions due to genetic factors
• Genetic control is highly indirect.
• Example with the rat rewiring its brain to repair damage.
• Brain Tracts and Differential Abilities
• Reading ability could be tied to brain wiring
• Nature vs. Nurture
• Genetics control roughly 1/2 of our brain traits.
• Someone who is predisposed to having a trait my still not develop that trait.
• Based on identical twin, fraternal twin and adopted sibling studies.

Notes on Chapter 8: The Tools of Thought

I found this chapter to one of the longer and more difficult to comprehend chapters in the book.  The basic ideas were intriguing, in particular:

• Memories are hierarchical.
• Recognition is a multi-stage, temporal process.
• Brains are naturally amenable to grammar like organization.

A basic concept used throughout the book is that larger brains lead to new abilities, even though the larger brain is just "more of the same" in that a larger brain does not have new or different structures, just larger versions of the same thing.

Thus, if memories are hierarchical, then a larger brain means more categories and deeper hierarchies.  If recognition is multi-stage, then a bigger brain can mean more stages and a finer distinction between otherwise identical items.  If brains and thought uses a grammar like structure, then a larger brain could mean a more elaborate grammar.

I find the notion of the "scavenger hunt" model for memory especially interesting.  While that approach seems especially strange, it does dovetail nicely with the associative nature of the brain: each "step" in a memory is an association.  Each association can be reused in different memories because they have a certain "momentum:" a memory is the sum of what came before plus the next association.

Chapter 8: The Tools of Thought

• Feedback and hierarchies of cortical circuits
• If our brains is the same as a mammal brain, just larger, how does it gain new abilities?
• Feedback Circuits
• The cortex is wired both from sensory systems to something else and from the cortex to the sensory systems.
• Can re-experience sensations without the actual stimulation.
• Can rearrange and examine the steps that are taken.
• Steps of Recognition
1. Initial Activation
• The flower example
• Sensory impression
• Contains more data than the brain can process
2. Learning
• Group different flowers into categories
• Group all flowers into plants
• Generalizing and differentiating
• Generalizing: flowers, plants, commonalities
• Differentiating: what makes a rose different from a daisy
3. Feedback
• Once a category is established, feedback suppresses differences
• Thalamus is involved in suppression
• Effect is that the cortex only sees the common aspects in the first sensation.
• Next sessions, the differences start to arise.
• Thus an instantaneous experience becomes a sequence of experiences.
• Sequences
• In addition to breaking a single sensation into multiple steps as per categories.
• Flower petal example: start with one petal, look for the next.
• Validate a possibility
• What One Brain Area Tells Another Brain Area
• Old tools are relatively crude
• EEG, PET scan, CAT scan
• Includes fMRI
• What's in an Image?
• Description of how fMRI works.
• Putting it Together: From Generalists to Specialists
• Fallacy: the wheels moving the car
• Something else actually turns the wheels
• Controversy over recognition
• Grandmother cells
• Specific cells encode information.
• Distributed
• populations of cooperating neurons represent information
• Memory Construction
• They advocate a hybrid approach between Grandmother cells an a distributed system.
• Distributed in the sense that no one neuron encodes a particular memory
• "Grandmother" like in that neurons do exist that are very highly tuned to a particular type of image
• A sort of "shared grandmother cell" approach.
• Building High-Level Cognition
• Large brains lead to long cortical processing areas.
• Libraries and Labyrinths
• Memories are stored as routes through the brain instead of one location that has all the data.
• Scavenger hunt analogy
• Grammars of the Brain
• The way the brain works is similar to a linguistic grammar
• There are rules that govern what sequences of thoughts are allowable
• Specific pathways store individual memories.
  

Notes on Chapter 7: The Thinking Brain

I found this to be a rather discordant chapter.  It starts by talking about evolution of the brain in terms of size and then switches over to a discussion of how the motor systems work. I think the point that the authors are trying to make is that the association regions got larger so that it would be possible to make more elaborate and detailed plans. 

Another point is that the brain deals with detail hierarchically.  With the pitching example, the planning portion of the brain deals with the high level concepts - use a slider pitch instead of a fastball - and then passes that command onto the next brain system.  That brain system selects the general set of movements required and passes each off to the motor portions.  The motor portions control the muscle movements for each step and cause the actual neural signals to be sent out.

The last part of the chapter portrays a struggle between the higher and lower portions of the brain for control.  The discussion is vaguely related to what came before (higher levels controlling lower levels) but it is portrayed more as a struggle than a cooperating system.  The authors note that the larger the brain is, generally the more control the higher portions of the brain have over the lower portions.

To illustrate the conflict aspect, the authors mention a movie where the conscious and subconscious minds are in what amounts to a pitched battle over control.

Chapter 7: The Thinking Brain

• Introduction
• How did we get big brains?
• Irish Elk analogy 
• Our brain is a scaled up version of a monkey brain
• Question becomes why are we so large?
• Mammal brains scale consistently
• Primate brains scale very predictably
• Extending thinking over time
• Various parts operate in concert
• The pitcher example
• Cortex: select a pitch
• Cortex tells the motor context 
• Motor cortex selects the individual, high level movements
• Motor cortex tells the striatum to perform a lower level movement
• Striatum initiates the individual movements with the body
• This is the basis for higher level planning
• The Cortex Takes Charge
• Larger cortex means more control over the lower portions of the brain and body.