The Workings of the Brain: Development, Memory, and Perception
Rodolfo R. Llinas (ed), 1990

Section I: Evolution and Form

Chapter 1. Paleoneurology and the Evolution of Mind
Harry J. Jerison

(from Sci Am Jan 76)
Jerison first discusses brain growth in the vertebrates and presents diagrams showing the relationships in brain/body mass for a wide variety of living and archaic mammals and reptiles. He also shows the related encephalization quotient for several mammals representing a range from "smart" to "stupid".

He then presents an interesting hypothesis that the evolution of intelligence was driven by a particular situation in the neural structure and the changing environment of the early mammals. A very early mammal-like reptile, the therapsid, would have had, like all vertebrates, a complex visual system which had significant neural structure within the retina itself for "preprocessing" the visual data. By contrast, hearing and smell were relatively less well developed systems, with all processing performed in the cortex rather than at the receptor organs. As the larger dinosaurs began to win the battle for a similar environmental niche, the descendants of the therapsids developed better hearing and olfaction systems in order to function better at night and leave the daytime to the dinosaurs. Since the auditory and olfaction processing was done cortically, this resulted in significant cortical development. Jerison then presents a simple scenario, of the type more recently known as a "just so story", of how these developments could have led to consciousness.

Imagine an early mammal coping with life at twilight, sensing stimuli from distant sources. The stimuli are recorded by reptile-like vision (modified toward the mammalian retina with rod cells for night vision), mammalian hearing and mammalian smell, all providing information from the same environmental source. It would obviously be adaptive if the information received from the different sensory modalities were given a common code, or label. The integrating code would work, in all likelihood, by the labelling of stimuli in the different modalities as coming from the same object in space at a particular time. And so we have the basic constructs of human conscious experience: objects in space and time.

Evolving to see at night was only the first of several hurdles to be crossed. Once the dinosaurs disappeared, new envolutionary niches opened up, particularly, daytime activity. By this time, the nocturnal creatures had lost some of the reptilian visual system. As a result, a new visual system developed, centered in the cortex, rather than the earlier midbrain system . It would presumably have been a significant selectional advantage to make use of the multimodal integrative systems which already existed, wiring the new visual responses into those integrative systems.

Much later, new and different forces caused the primate branch of the family of mammals to experience additional new cortical growth. These ideas are not presented in the rich detail as are the earlier developments.

Chapter 2. The Organization of the Brain
Walle J. H. Nauta and Michael Feirtag

(from Sci Am Sep 79, also appears in an expanded form as Part II of
Fundamental Neuroanatomy )
The centerpiece of this chapter is a series of illustrations showing the pathways and connections of many of the major axonal tracts of the brain. The accompanying text is like a play-by-play analysis of each tract shown in the figures, with commentary on the nueral types, the nature of the connections, and to some extent, the functionality of the tract.

This set of figures is supported by a number of photographs and other drawings showing details of a neuron, brain sections, and other anatomical detail. As I have said in the FN review , I would very much like to see a 2001 version of this material.

Section II: Development and Plasticity

Chapter 3. The Development of the Brain
W. Maxwell Cowan

(from Sci Am Sep 79)
This chapter offers a good view of the issues of brain development. How do the hundreds of thousands of neurons which grow every minute in the brain of a developing fetus figure out where to go?

Chapter 4. The Development of Maps and Stripes in the Brain
Martha Constantine-Paton and Margaret I. Law

(from Sci Am Dec 82)
A million or so neurons in the retina send their axons to a region of the tectum during the development stage in many animals. How do they know where to go? The authors describe a number of hypotheses, such as various distributions of chemical markers with matching receptors in the target area, and other methods which depend on axonal firing patterns in the growing optic nerve.

During the 60's and 70's, many experiments were performed to investigate this matter. If the eye-buds of a tadpole are rearranged in various ways, they will grow into well-formed eyes in the adult frog and make connections to the tectum in testable patterns. For example, if an extra eye-bud is attached to the top of the tadpole's head, the adult frog will have a third eye on the top of its head. The axons from this extra eye will intermingle with the axons from the two normal eyes. If this frog's normal eyes are covered and a moving bug-like spot displayed to the third eye, the frog will react by striking in a direction corresponding to the original orientation of the tadpole eye-bud.

The various nerve growth hypotheses are considered with respect to the results of the eye rearrangement tests. The authors conclude that the nerves must use a combination of 2-axis hormonal gradients for the initial growth, followed by a fine-tuning which consists of the detection at the tectum of optic nerve firing patterns which represent the correlated illumination of adjacent regions of the retina.

Section III: Emotion and Memory

Chapter 5. The Reward System of the Brain
Aryeh Routtenberg

(from Sci Am Nov 78)
James Olds, in 1977, published work showing that a rat with an electrode implanted in a particular region of the brain and connected to a lever in the rat's cage would continue to press the lever to activate the electrode to the exclusion of food, sleep, and all other bodily necessities, until it dropped from exhaustion. Since that time, the brain's reward systems have been extensively studied. Routtenberg takes us on a tour of the dopamine and norepenephrine distribution systems and the effect these and other chemicals have on learning and feelings of happiness, depression, self-assuredness, or anxiety. Along the way, we learn about some of the brain regions involved in memory formation and maintenance.

Chapter 6. The Anatomy of Memory
Mortimer Mishkin and Tim Appenzeller

(from Sci Am Jun 87)

Section IV: Of Symmetry, Imaging and Dreaming

Chapter 7. Specializations of the Human Brain
Norman Geschwind

(from Sci Am Sep 79)

Chapter 8. Turning Something Over in the Mind
Lynn A. Cooper and Roger N. Shepard

(from Sci Am Dec 84)
This now classic paper presents Cooper and Shepard's revealing experiments in which they measured the length of time it took subjects to decide whether a pitcure of a 3-D object represented the same object as a second picture, where the object (or another) appeared with a different spatial orientation. They found that the decision time was nearly proportional to the angle of rotation needed to bring the objects into the same orientation.
Anderson has related these results to his production system model of cognition.

Chapter 9. A Window on the Sleeping Brain
Adrian R. Morrison

(from Sci Am Apr 83)

Section V: Brain Models

Chapter 10. Collective Computation in Neuronlike Circuits
David W. Tank and John J. Hopfield

(from Sci Am Dec 87)


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