The Shallows: What the Internet Is Doing to Our Brains

by Nicholas Carr

One of the simplest yet most powerful demonstrations of how synaptic connections change came in a series of experiments that the biologist Eric Kandel performed in the early 1970s on a type of large sea slug called Aplysia. (Sea creatures make particularly good subjects for neurological tests because they tend to have simple nervous systems and large nerve cells.) Kandel, who would earn a Nobel Prize for his work, found that if you touch a slug’s gill, even very lightly, the gill will immediately and reflexively recoil. But if you touch the gill repeatedly, without causing any harm to the animal, the recoiling instinct will steadily diminish. The slug will become habituated to the touch and learn to ignore it. By monitoring slugs’ nervous systems, Kandel discovered that “this learned change in behavior was paralleled by a progressive weakening of the synaptic connections” between the sensory neurons that “feel” the touch and the motor neurons that tell the gill to retract. In a slug’s ordinary state, about ninety percent of the sensory neurons in its gill have connections to motor neurons. But after its gill is touched just forty times, only ten percent of the sensory cells maintain links to the motor cells. The research “showed dramatically,” Kandel wrote, that “synapses can undergo large and enduring changes in strength after only a relatively small amount of training.”19

Now i have to read In search of Memory by Eric Kandel. It has been in Vivaldi (wink) for days.