The Ecology of Humans (26-14) Plasticity


The same areas of the brain active while recognizing faces are similarly astir during recognition of different models of cars and trucks. The pattern matching of categorization is a primary mental activity, irrespective of what it is classifying.

Mental skills a matter of memory and of forgetting. Bad habits can be difficult to unlearn. Repeated activation of brain areas involved in the exercise of habits acts as physiological reinforcement. Hence the cruciality of discipline in developing and maintaining healthy habits.

We are what we repeatedly do. Excellence, then, is not an act but a habit. ~ American historian Will Durant

The mind-brain is capable of adaptation throughout life, especially so during the early, formative years.

Brain areas and connections are allocated to skills that are practiced. What has been learned may be lost with disuse. As life progresses, brain plasticity is a discipline: use it or lose it. The brain is literally the muscle of mentality: able to adapt and grow with proper nourishment and exercise.

Brain power improves by brain use, just as our bodily strength grows with exercise. ~ English writer A.N. Wilson

Autopsies have shown that educated animals have more neural branches. This increase in branches drives neurons farther apart, giving the brain body by greater volume and thickness.

Deficiency or change in one brain module cascades to functional and structural changes in other brain modules. The brain adapts: becoming more acute to compensate for a deficiency elsewhere. By blindfolding people, German neurologist Alvaro Pascual-Leone demonstrated that the occipital lobe, which normally processes vision, could alternately process sound and touch.

American neurobiologist Michael Merzenich investigated “false localization” in the 1980s. When a large peripheral nerve bundle is cut, wires can get crossed during nerve regeneration, as axons reattach in a different pattern than before the injury. When this happens while healing a person may experience sensory dislocation. A cut in the arm can result in the thumb feeling touched when it was actually the index finger. This can last for months. As nominal brain mapping is geographically oriented, this phenomenon makes sense from a localization perspective: that the brain map corresponds to a point-to-point model.

What Merzenich discovered by mutilating monkeys was that the nervous system heals in time by straightening the crossed signals. Merzenich observed that the topological brain maps of the healed monkeys were in a slightly different location than before the injury.

If the brain can remap and normalize after injury, the idea that the brain is hardwired must be wrong. Brain processing must be plastic.

The brain is plastic in at least 4 known ways: the number of neurons, the network connections between neurons, the way in which neurons massage signals, and the speed at which signal processing occurs. The physical adjunct of learning is a process that often involves changes in all ways: new cells grow, processing patterns change, the network of circuits connecting modules are altered, such that changes in one area of the brain flows to another, and, with rote practice, the speed of processing increases.

Diverse kinds of sensory energy stimulate receptors, such as the skin sensing vibration, moisture, pressure, or temperature; light beaming the retina; and vibrations onto hairs deep in the ears. These sense receptors translate various input types into signals carried by nerve cells, which employ a combination of electrical and chemical energy to transmit data bits to the mind-brain. Glia cells in the brain are busy as the bits are collated and analyzed. The mind-brain works by memory-based pattern matching, filling in gaps as necessary. This is the nature of optical illusions.

Much of the mind-brain appears polysensory: able to process incoming data patterns from more than 1 source. These patterns are the universal language of the mind-brain.

There are no visuals, no sounds, et cetera, moving through the neural network to the brain. This is a definitive indication that the brain is merely a cohort to the mind, as a purely physiological explanation of sensation is impossible.

Areas of the brain are interconnected plastic processors, capable of handling a variety of inputs from multiple sources. A blind man probing with a cane causes repeated vibrations in his hand, which transmit signals to his brain, allowing a pattern in the mind-brain to emerge from sensed obstacle points where the cane touched something. The mind-brain patterns tactile points together geographically based upon the angles of the hand and wrists corresponding to the timing of touches. Different senses of skin pressure and muscular exertion are coupled together in the mind-brain as a patterned signal. These multiple patterns from different sensory complexes are processed in the portion of the brain used by sighted people for vision.

Like echolocation, the cane acts as eyes. Cane taps are like photons on the retina: crude pictures by comparison, but sight nonetheless. American neurobiologist Paul Bach-y-Rita understood that “we see with our brains, not with our eyes.”

American neurobiologist Vernon Mountcastle discovered that the human cerebral cortex comprises a 6-layer processing structure, referred to as a cortical column. Dolphins have a 5-layered cortical column, while reptiles have 3 layers.

The visual, auditory, and sensory cortices all use the same processing structure. Such consistency makes perfect sense from an evolutionary viewpoint, where modular similarity is a norm.

Processing in the sensory cortex is plastic and adaptable. The cerebral cortex, the thin outer layer of the brain, if kept active, selectively refines its processing capacities to fit each task at hand.

As new material is learned, network connections become more efficient in stages. First, brain maps enlarge to accommodate mastering the subject or task at hand. With practice, though the same number of glial cells may conduct, fewer neurons are needed to perform the task. Maps become more precise. Discrimination is enhanced.

Further, as the learning is reinforced, processing speeds up: which means that the speed of thought is plastic. Reaction time is more than reflex, as any sports player can tell you: it is the mind-brain in action.

Speed of thought is a critical component of intelligence. The more quickly processing transpires, the more information that can be absorbed and considered in decision-making.

Besides sheer speed, training results in more defined intelligence cell connections and greater synchrony. This give clearer, more powerful signals. The physiological signal-to-noise ratio of thought goes up.

One limiter always remains. The quality of memory is only as good as an individual’s perceptiveness.

Learning itself is not casual. Instead, paying close attention is essential to effecting long-term plastic improvement.

Acetylcholine – a neurotransmitter necessary for learning – flows freer the more difficult the learning. Dopamine – the brain’s reward chemical – plays a role consolidating memories. Acetylcholine sharpens while dopamine reinforces.