Notes on Chapter 5: Brains of Mammals

This chapter was fairly short but it was also pretty focused on describing how the various mechanisms of the brain work. 

Associative Cortical Circuits
A central concept to the book is the idea that there are two broad categories of sensory processing regions in the brain: point to point and "random access" (I refer to this as associative).  The idea is that, for systems like the motor regions, if one muscle is physically situated near another muscle, then the corresponding brain regions will also be located near each other.

This is not the case for the brain region that processes the olfactory senses.  Instead that region follows what the authors call a "random access" scheme.  In that arrangement, while the primary sensory inputs are point to point, they quickly lose that aspect.  For example, the scent of oranges might be associated with food, or the scent of a mountain lion could be associated with the notion of danger.

I call this arrangement "associative" because it hearkens to the notion that a primary sensation (in this case a smell) is associated with something else. 

Why would being warm blooded help "absorb the cost" for having a large brain?
The authors mention several times that having a large brain is biologically expensive.  One issue is the number of calories consumed by neuronal tissues.  I suppose one reason that being warm blooded might help is that, if the organism is going to be consuming a lot of calories to keep the body at a constant temperature, then the cost of having a large brain would be, proportionally speaking, smaller.

Nevertheless, it seems to me that an organism that needs additional calories to support itself because of a large brain would still be at a disadvantage relative to one that had a smaller brain.