What Internet Doing With Our Generation’s Minds?

During the 20th century, neuroscientists and psychologists developed a more complete picture of the staggering complexity of the human brain. They found that within our skulls house about 100 billion neurons, which take many different shapes and range in length from a few tenths of a millimeter to about a meter. A typical individual neuron has many dendrites, and dendrites and axons have myriad branches and synaptic endings. An average neuron makes about a thousand synaptic connections and some of them can make a hundred times that number. The millions of billions of synapses inside our skulls bind neurons together in a dense network of circuits that, in ways we are still far from understanding, give rise to what we think, how we feel, and who we are. Even with advances in knowledge about the physical functioning of the brain during the 20th century, an old assumption remained unchanged: most biologists and neurologists continued to believe, as they had for hundreds of years, that the structure of an adult brain never changed. Our neurons would connect into circuits during childhood, when our brains are malleable, and by the time we had reached maturity, the network of circuits would have fixed. The brain, according to the dominant view, was like a concrete structure. After being poured and molded during our youth, it would quickly harden into its final form. Once we were in our twenties, no new neurons would be created, or new circuits forged. We would continue, of course. While the belief in the immutability of the adult brain was widely accepted and deeply held, there were a few heretics. A handful of biologists and psychologists saw in the rapidly growing stream of brain research indications that even an adult brain was malleable, or "plastic." New neural circuits could form over the course of our lives, they suggested, and the old ones could strengthen, weaken, or disappear entirely. British biologist JZ Young, in a series of lectures broadcast by the BBC in 1950, maintained that the structure of the brain could indeed be in a constant state of fluidity, adapting to whatever task was asked of it. "There is evidence that our brain cells literally develop and get bigger with use, and they atrophy and are discarded with disuse", he said. "Therefore, it may be that every action leaves some permanent impression on the nervous tissue." Young was not the first to propose such an idea. Seventy years earlier, American psychologist William James expressed a similar intuition about the brain's adaptability. "Nervous tissue", he wrote in his fundamental work, Principles of Psychology, "seems endowed with a very extraordinary degree of plasticity". As with any other physical compound, "either external forces or internal tensions can suddenly turn that structure into something entirely different from what it was before." James quotes, giving his nod, an analogy that French scientist Leon Dumont, in an earlier essay on the biological consequences of habit, traced between the actions of water on land and the effects of experience on the brain: "Running water digs by itself a channel that becomes wider and deeper; and when, later, it flows again, following the path traced by itself previously. Likewise, the impressions of external objects themselves shape the most appropriate pathways in the nervous system, and these vital pathways recur under external stimulation, even if they have been interrupted for some time." Freud, too, ended up taking a similar position.