Nature’s Brains, Part 4

July 8, 2012

Bob Fiske

Nature’s Brains, Part 4

(Note: I invite you to read Part 3 before you dive into this part.)

Sooner or later, in nature’s tinkering with brain designs, a truly superior model was bound to come along.  The simian family lays claim to this prize.  Scientists don’t really understand how this happened, yet we see many descendent species alive today that clearly show the innovative features that formed over time.

One of these innovations was exquisitely fine motor control.  This capability appears to have co-evolved with body characteristics that could express new types of movement.  For instance, all monkeys and apes possess a finger-based hand that shapes itself with greater precision than is given to clawed or hooved mammals.  Also, some of these species are endowed with long limbs and tails that give them the arboreal advantage to swing, climb and hang.  Of course, living in trees also requires balance, eyesight and hearing to match the motor skills.  These are jobs handled by the new brain, and they couple well with this brain’s superior learning ability.

Courtesy of e-mail, I once watched a film of a gibbon teasing a pair of tiger cubs.  (You may watch it here, though be warned that the film quality is low.)  If ever I saw a gymnastic wizard, this little gibbon was it.  It is a remarkable testimony of the superior level of body-and-brain coordination possible using a simian brain.

Other capabilities emerged in the simian brain.  A brain that can learn is a brain that can teach.  Thus, it is possible to pass brain-encoded patterns from generation to generation without relying only on the DNA hard-wiring of behavior.  By the way, the teaching of new generations is not a monopoly owned just by simian brains.  Bears teach their cubs how to forage, and many types of young male birds must learn their songs from older males of the same species and geographic location.  Nonetheless—as we well know—the simian brain would push the ability to learn and teach to new heights.

The most recent brain innovations are sported by the hominids, or great apes.  Some of our less intellectual cousins, chimpanzees and gorillas, show that they, too, carry the seeds of the type of intelligence that flourished in the Homo (human) line.  Chimps have been observed to make simple tools such as using sticks to fish out ants from a nest for eating.  These species show other “human” traits such as problem-solving, concern for the welfare of others, and self-awareness.

And, surprisingly, both chimpanzees and gorillas have revealed that they possess previously unsuspected symbolic language skills.  Given the right expressive media (American Sign Language, computer screens or colored shapes), hominids in research settings have amassed sizeable vocabularies and have shown that they can fashion novel “utterances” to express, wants, needs and general observations.

Finally in this discussion of the “advanced design” hominid brain, I wish to mention a series of brain structures that are loosely bundled under the term “the limbic system”.  The limbic structures lie at the base of the cortex, at the juncture where it surrounds the “old brain”.  In fact, these structures (the hippocampus, the amygdala, the nucleus accumbens, and others) appear in other mammalian brains of less intellectual stature than the hominid brain.  In spite of this fact, it is probable that, in hominid brain design, limbic structures were enhance and pressed into service to perform more complex functions.  Limbic functions are thought to play a role in reward, fear, addiction, emotional memories and memory formation in general.  Perhaps that’s too much anatomy.

The idea I want to paint about the new-and-improved hominid brain might be better conveyed using broader brush strokes.  This brain permitted a new level of behavioral and thought patterns, patterns that were the product of emotions, punishments, rewards and social transactions.  In ape communities we see such things as exchanging grooming services, currying favor and shifting dominance hierarchies.  However, in human communities an entirely new social reality was called into existence.  Its final metamorphosis would be expressed in human culture.  In this culture the social, emotional, symbolic, political, artistic, economic and intellectual components could take on reality as  by-products of a marvelously large brain.

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Nature's Brains, Part 3

July 8, 2012

Bob Fiske

Nature’s Brains, Part 3

(Note: I invite you to read Part 2 before you dive into this part.)

As nature continued to tinker with brain designs, sooner or later some sophisticated features were bound to arise.  In larger, brained animals, such as dinosaurs, the reptilian or “old brain” did little more than regulate basic bodily processes.  These brains sent “down” nerve impulses for modifying respiration, digestion, heart rate, and perhaps even body temperature.  The old brain could also chain together primitive movements known as reflexes.  Reflexes are simple and are coded in the spinal cord.  Through the dominance of the brain these simple movements could be orchestrated into more complex behavioral sequences, sort of like composing words from the letters of the alphabet.

The complex behavioral sequences could accomplish tasks such as hunting, mating, building a nest, walking, running, fighting, and so on.  How did the old brain come to encode the complex behaviors?  Through trial-and-error.  In other words, species went extinct or found a survival advantage based upon the behavior sets that were genetically hard-wired into their members’ brains.  These behaviors were determined by the DNA code in that species’ genes and were passed from generation to generation.  Learning of the sort that we take for granted had not yet been invented as a brain design feature.

Even today we are able to see in the “advanced” mammalian brain vestiges of hard-wired, genetically coded behavior.  One example of this is the newborn foal.  Within minutes of being born, baby horses struggle to their feet and begin to walk.  Seeing a fully developed behavior of this sort is fairly unusual in the mammalian brain because the innovations it has acquired generally impose a long development period on the young brain.

One of the premier innovations that enabled mammals to survive was the brain’s ability to learn.  This is anything but trivial (even though we take it for granted).  In order to learn, the brain needed to have a memory that could be loaded with new patterns.  But, for that to happen, the brain required an exquisitely complex coding mechanism that could replicate, in a “neural form”, qualities of the real world, a virtual model, so to speak.  This required more and more neurons in the brain.  The result is the “new” brain, a larger accessory that physically sits above and around the old brain.  All this new neural tissue was crammed into a larger skull in a folded and wrinkled fashion.  Scientists call this the cortex.

Parts of the cortex could more richly record auditory information or visual information.  Also, parts of the cortex were dedicated to producing complex movement sequences in various muscle groups such as the limbs, the mouth, the tail, the vocal chords, etc.

By the way, mammalian brains exerted pressure on other species to keep up.  So, we see that many birds (the descendants of the dinosaurs) also innovated their brain designs in similar fashion.  Maybe we mammals are not so special, after all, just lucky to come out in front of the race for survival.

Of course all this ability to encode a rich a faithful inner world model or command exquisitely complex movements would be better utilized if the brain were endowed with an equally rich storage system, that is, a memory.  The memory would allow multiple experiences in an individual’s life to be compared.  This is essential to learning (and survival), for it enables the search for cause-and-effect relationships to be found.

Here’s a simple example.  I am travelling with a herd of my companion mammals over an area of dry, parched earth.  Yet my eyes and visual cortex are able to discern a distant spot of green and brown as a concentration of things known as plants.  The brain, commanding the eyes to look more closely, enables the visual cortex to spy that this is a rich and dense collection of vegetation.  And the brain’s memory yields up a “conclusion” that other dense collections of vegetation have proved to be a source for water.  Even without the benefit of language that can name things, my mammalian brain has recorded (learned) the causal meaning of an oasis.

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