The Executive Brain by Elkhonon Goldberg - 2001

The Executive Brain: Frontal Lobes and the Civilized Mind

Elkhonon Goldberg

This is a book mostly about the human pre-frontal cortex by a leading psychological neurologist who escaped from the Soviet Union. So not only will you get some brain information but also the story of the author's professional life.

To hear an podcast interview with Elkhonon Goldberg by fellow Voxer Ginger Campbell go here.

The prefrontal cortex has two functions. A motivation defining function in which basic internal motivations (goals) are modified and refined to conform with the external environment and an executive function in which a coordinated set of actions and thoughts are defined and maintained. Like all cortex regions the prefrontal cortex extends the abilities of  certain sub-cortical regions.

In the case of the executive function the reticular formation in the brain stem is its sub-cortical analog. The hypothalamus feeds fundamental motivation signals (food search, flee, mate, security search, etc) into the reticular formation which based upon environmental conditions regulates the expression of various actions. For example, slowly increasing electrical stimulation of the Hypothalamic region in birds that initiates the flee response will first trigger a walk, then a run, then a flight. If the bird is trapped then it will fight. These actions are all part of a coordinated set belonging to the response.

The conformance of motivation signals to the environment has their subcortical analogs as well. These subcortical regions include the amygdala, septum, and others. This is discussed in my review of The Emotional Brain.

The prefrontal cortex accounts for 29% of the total cortex in humans, 17% in the chimpanzee, 11.5% in the gibbon, 8.5% in the lemur, 7% in the dog, and 3.5% in the cat. (page 33)

For me the most significant new idea was Goldberg's suggestion that the underlying difference between the two brain hemispheres is based upon their learning rate in response to novelty (page 40). In all learning, a system has to make a trade-off between the speed of learning and the accuracy of learning. Those associations, as formed by conditioned learning, formed after only one or a few observed event correlations have a high probability of being wrong (the correlation could just be a coincidence) compared to associations formed after a longer observation time. It would be advantageous for any animal to be able to work with either the uncertain or certain associations depending on the task at hand. This pre-adaptation of the hemispheres is why language is most often found on the left side because of the tight context rules for grammar. Setting up a context involves making many more associations that cannot be contradictory if context control is to work. In contrast the right side of the brain would tend to be the more intuitive  since it works with uncertain associations but these are associations that would not yet exist on the left side. Brain scan observations show that the right hemisphere is more active when a task is novel while the left hemisphere is more active when the task is practiced (page 49).

Interestingly males (40% to 22%) exhibit more context dependent decision making than females (15% to 12%) in a test called the Cognitive Bias Task (page 90). In this test a "target" object was shown along with 2 choice objects. The subjects had to choose the object they liked the most. The choice strategies tended to be consistent for each individual subject with the context dependent types choosing the object most similar to the target object. In contrast the context independent types would choose objects based upon color, shape, or some other parameter. Still context types are a minority in both genders.

Males with damaged right frontal lobes behaved in an extremely context dependent fashion while those with damaged left frontal lobes behaved in an extremely context independent fashion. In contrast damage to either lobe in females produced extremely context dependent behaviors (page 95).

The two major syndromes (or end points in a damage continuum) that arise from damage to the prefrontal cortex correspond to deficits in one of the two prefrontal cortex functions. The dorsolateral syndrome (chapter 8) comes from damage to the medial areas of the prefrontal cortex and it produces pseudo-depression. Like depression this patient has an inability to initiate behaviors. Yet when behaviors can be induced after much effort they tend to persist without stopping.  In severe cases the patient will lie passively in bed, neither eating nor drinking. Patients with this syndrome are no longer bothered by pain even though they can describe the pain they feel just like normal people. Most of these patients will also have Anosognosia in which they are unable to recognize their limitations with the result that they have no motivation to undergo rehabilitation excercises. Minor or slowly developing dorsolateral syndromes can be very hard to recognize since people assume that the person is becoming lazy or simply disinterested in things due to age.

The orbitofrontal syndrome (chapter 9) is a condition in which the patient is emotionally disinhibited and impulsive. They are not able to defer immediate gratification and cannot see the consequences of their actions. They will say what is on their minds without regard to the social consequences as well. If these actions seem childish, well, they are. The prefrontal cortex is the last brain region to mature and it does not become mature until around age 18 (page 144). The author also discusses the consequences of this sort of pre-frontal cortex damage in regards to criminal responsibility.

Chapter 10 describes the groundbreaking investigation of "Kevin" who because of a horse fall damaged his reticular formation and the temperoparietal brain regions (thus his reduction in ability to form new memories). After Keven had recovered physically from the event he still had the following mental deficits (Page 158).

"Keven was perseverative: that is, his behavior invariably fell into repetative stereotypes. Every evening he would arrange his clothes for the following day and the clothes were always the same.... Despite his superficial flair, any conversation with Kevin rapidly deteriorated into a rather vacuous activity such as simple card games. He had a small repertoire of rehearsed stock topics, and the conversation would predictably and quickly drift toward one of them, say, a discussion of some of his friends.

"In the restaurant he tended to order every item on the menu, 10 or 20 items in all .... He spent most of his time though, languishing in his apartment, occasionally asking people to play simple card games .... His behavior during the games was childlike. He would clap his hands with joy after winning and throw temper tantrums after losing. He was not above cheating.

"Keven's affect (mood) was constantly oscillating between euphoria and superficial rage. These mood swings were abrupt, extreme, and could be precipitated by the most trivial events - like a waitress in a restaurant asking him if he wanted more coffee"

"Kevin had no insight into his condition"

"Kevin's mind was astoundingly concrete. When I once said that it was time to repeat the AT scan, this was meant with genuine puzzlement. Why the CAT scan, Keven marveled, if after all he had been hurt by a horse, not a cat?"

Second generation CAT scans showed Kevin's ventral tegmental region of the reticular formation was completely destroyed. This region sends massive amounts of dopomine neurons to the prefrontal cortex (page 161) probably for the purpose of defining the top level motivational contexts which the frontal cortex then refines.

Overall another great book for one's neuroscience collection.