1. A Woman Perpetually Falling
Vestibular apparatus: the sensory organ for the balance system.
“We have senses we don’t know we have-until we lose them;…The balance system gives us our sense of orientation in space. Its sense organ, the vestibular apparatus, consists of three semicircular canals in the inner ear that tell us when we are upright and how gravity is affecting our bodies by detecting motion in three-dimensional space….A healthy vestibular apparatus also has a strong link to our visual system.” [Does this mean any creature that could feel more than three dimensional space-time must have structural difference compared to us?]-p3
“Paul Bach-y-Rita rejected these localizationist claim. Our senses have an unexpected plastic nature, he discovered, and if one is damaged, another can sometimes take over for it, a process he calls ‘sensory substitution’…By discovering that the nervous system can adapt to seeing with cameras instead of retinas, Bach-y-Rita laid the groundwork for the greatest hope for the blind: retina implants, which can be surgically inserted into the eyes.”-p13
Broca’s area: was presumed to coordinate the movements of the muscles of the lips and tongue. -p16
Wernicke’s area: the ability to understand language. -p16
“Bach-y-Rita began to conceive of much of the brain as ‘polysensory’-that its sensory areas were able to process signals from more than one sense….This can happen because all our senses receptors translate diffrent kinds of energy from the external world, no matter what the source, into electrical patterns that are sent down our nerves. These electrical patterns are the universal language ‘spoken’ inside the brain.”-p18
“Bach-y-Rita, based on his knowledge of nerve growth, began to argue that these learning plateaus were temporary-part of a plasticity-based learning cycle-in which stages of learning are followed by periods of consolidation. Though there was no apparent pprogress in the consolidation stage, biological changes were happening internally, as new skills became more automatic and refined.”-p24
“Andy Clark wittly argued that we are ‘natual-born cyborgs,’ meaning that brian plasticity allows us to attach ourselves to machines, such as computers and electronic tools, quite naturally.”-p26
2. Building Herself a Better Brain
“Up through the nineteenth and early twentieth centuries, a classical education often included rote memorization of long poems in foreign languages, which strengthened the auditory memory (hence thinking in language) and an almost fanatical attention to handwriting, which probabaly helped strenghten motor capacities and thus not only helped handwriting but added speed and fluency to reading and speaking. Often a great deal of attention was paid to exact elocution and to perfecting the pronunciation of words. Then in the 1960s educators droped such traditional exercises from the curriculum, because they were too regid, boring, and ‘not relevant’. But the loss of these drills has been costly; they may have been the only opportunity that mant students had to systematically execise the brain function that gives us fluency and grace with symbols. For the rest of us, their disapearance may have contributed to the general decline of eloquence, which requires memory and a level of auditory brain power unfamiliar to us now.”-p41-42
Acetylcholine: a brain chemical essential for learning.
3. Redesigning The Brain
“Michael Merzenich‘s specialty is improving people’s ability to think and perceive by redesigning the brain by training specific processing areas, called brain maps, so that they do more mental work….Of neuroplasticians with solid hard-science credentials, it is Merzenich who has made the most ambitious claims for the field: that brain exercises may be as useful as drugs to treat diseases as severe as schizophrenia; that plasticity exists from the cradle to the grave; and that radical improvements in cognitive functioning-how we learn, think, perceive, and remember-are possible even in the elderly.”-p46
“Normally, when one’s hand is touched, an electrical signal passes to the spinal cord and up to the brain, where it turns on cells in the map that make the hand feel touched.”-p48
Dr.Wilder Penfield, in the 1930s, made sensory and motor brain maps, “like geographical maps, are topographical, meaning that areas adjacent to each other on the body’s surface are generally adjacent to each other on the brain maps…..but Merzenich discovered that these maps are neither immutable within a single brain nor universal but vary in their borders and size from person to person.”-p49
Vernon Mountcastle, a famous neuroscientist at Hopkins in the 1950s, is Merzenich’s advisor by then. Vernon “demonstrated that the subtleties of brain architecture could be discovered by studying the electrical activity of neurons using a new technique: micromapping with pin-shaped microelectrodes.”-p50
Micromapping pro: about a thousand times more precise than the current generation of brain scans, which detect bursts of activity that last one sec in thousands of neurons. A neuron’s electrical signal often lasts a thousandth of a second, so brain scans miss an extraordinary amount of information.
Micromapping con: micromapping hasn’t replace brain scan because it requires an extremely tedious kind of surgery, conducted under a microscope with microsurgical instruments.
“David Hubel and Torsten Wiesel were micromapping the visual cortex to learn how vision is processed….They also discovered that there was a ‘critical period’, from the third to the eighth week of life, when the newborn kitten’s brain had to receive vision stimulation in order to develop normally….Clearly the brains of the kittens during the critical period were plastic, their structure were literally shaped by experience.”-p51
“It also seemed that each neural system had a different critical period, or window of time, during which it was especially plastic and sensitive to the environment, and during which it had rapid, formative growth.”-p52
“It is important to understand that the nervous system is divided into two parts. The first part is the central nervous system (the brain and spinal cord), which is the command-and-control center of the system; it was thought to lack plasticity. The second part is the peripheral nervous system, which brings messages from the sense receptors to the spinal cord and brain and carries messages from the brain and spinal cord to the muscles and glands. The peripheral nervous system was long known to be plastic; if you cut a nerve in your hand, it can ‘regenerate’ or heal itself.”-p53
Each neuron has three parts:
- The dendrites: treelike branches that receive input from other neurons.
- Dendrites lead to cell body: sustain the life of the cell and contains its DNA.
- Axon: a living cable with varying lengths (from microscopic lengths in the brain, to some that can run down to the legs and reach up to six feet long.) Axons are often compared to wires because they carry electrical impulses at very high speeds (from 2-200 miles per hour) toward the dendrites of neighboring neurons.
A neuron can receive two kinds of signals: those that excite it and those that inhibit it.
- A neuron receives enough excitatory signals from other neurons, it will fire off its signal.
- A neuron receives enough inhibitory signals, it becomes less likely to fire.
“When we say that neurons ‘rewire’ themselves, we mean that alterations occur at the synapse, strengthening and increasing, or weakening and decreasing, the number of connections between the neurons.”