Axons Quotes

it occurred to him that kids were better at almost dying, and they were also better at incorporating the inexplicable into their lives. They believed implicitly in the invisible world. Miracles both bright and dark were to be taken into consideration, oh yes, most certainly, but they by no means stopped the world. A sudden upheaval of beauty or terror at ten did not preclude an extra cheesedog or two for lunch at noon.

"But when you grew up, all that changed. You no longer lay awake in your bed, sure something was crouching in the closet or scratching at the window ... but when something did happen, something beyond rational explanation, the circuits overloaded. The axons and dendrites got hot. You started to jitter and jive, you started to shake rattle and roll, your imagination started to hop and bop and do the funky chicken all over your nerves. You couldn't just incorporate what had happened into your life experience. It didn't digest. Your mind kept coming back to it, pawing it lightly like a kitten with a ball of string ... until eventually, of course, you either went crazy or got to a place where it was impossible for you to function. ~ Stephen King

A major push is under way to figure out the molecular basis of those "critical" or "sensitive" periods, to figure out how the brain changes as certain learning abilities come and go. In some, if not all, of those mammals that have the alternating stripes in the visual cortex known as ocular dominance columns, those columns can be adjusted early in development, but not in adulthood. A juvenile monkey that has one eye covered for an extended period of time can gradually readjust its brain wiring to favor the open eye; an adult monkey cannot adjust its wiring. At the end of a critical period, a set of sticky sugar-protein hybrids known as proteoglycans condenses into a tight net around the dendrites and cell bodies of some of the relevant neurons, and in so doing those proteoglycans appear to impede axons that would otherwise be wriggling around as part of the process of readjusting the ocular dominance columns; no wriggling, no learning. In a 2002 study with rats, Italian neuroscientist Tommaso Pizzorusso and his colleagues dissolved the excess proteoglycans with an antiproteoglycan enzyme known as "chABC," and in so doing managed to reopen the critical period. After the chABC treatment, even adult rats could recalibrate their ocular dominance columns. ChABC probably won't help us learn second languages anytime soon, but its antiproteoglycan function may have important medical implications in the not-too-distant future. Another 2002 study, also with rats, showed that chABC can ~ Gary F. Marcus

The full sequence of communication between neurons is thus usually electrical-chemical-electrical: electrical signals coming down axons get converted into chemical messages that help trigger electrical signals in the next cell. There are also synapses through which communication between presynaptic and postsynaptic sites is purely electrical, but chemical transmission is the more prevalent form. Thus, much of what the brain does involves electrical-to-chemical-to-electrical coding of experience. As hard as it may be to imagine, electrochemical conversations between neurons make possible all of the wondrous (and sometimes dreadful) accomplishments of human minds. Your very understanding that the brain works this way is itself an electrochemical event. ~ Joseph E. LeDoux

During the twentieth century, neuroscientists and psychologists also came to more fully appreciate the astounding complexity of the human brain. Inside our skulls, they discovered, are some 100 billion neurons, which take many different shapes and range in length from a few tenths of a millimeter to a few feet.4 A single neuron typically has many dendrites (though only one axon), and dendrites and axons can have a multitude of branches and synaptic terminals. The average neuron makes about a thousand synaptic connections, and some neurons can make a hundred times that number. ~ Nicholas Carr

The human brain is estimated to have about a hundred billion nerve cells, two million miles of axons, and a million billion synapses, making it the most complex structure, natural or artificial, on earth. ~ Tim Green