DO WE EVER STOP LEARNING?

摘要

SINCE AT LEAST THE 1500s, THE ADAGE "You can't teach an old dog new tricks" has preached the impossibility of schooling older folks. The trope still manages to color stereotypes of aging as more of a downhill slide than a journey toward wisdom. But 16th-century know-it-alls didn't have access to 21st-century neuroscience, and a growing body of research suggests that late-in-life learning is likelier than Renaissance pundits could ever have imagined. In fact, education does an aging noggin good. Our brains are bafflingly complex at any age. The average adult has around 86 billion neurons, connected by synapses-tiny gaps where these cells exchange chemical signals. Each head hums with hundreds of trillions of these connections, all sending and receiving tiny bits of information and instructions. During the 20th century, imaging tools like MRIs and BEGs finally let neurologists examine how those paths change as our minds mature, and they revealed that ageist notions of doddering seniors were quite mistaken. Throughout life, our noggins constantly rewire themselves. Some scientists suspected as much as far back as the late 1800s. But it wasn't until the late 1960s, when British neuroscien-tist Geoffrey Raisman spied growth in damaged cerebral regions of rats through an electron microscope, that anyone managed to catch them forging new connections-an ability called neuro-plasticity. "Molecular changes occur each time we learn something new," says Kaitlin Casaletto, a neuropsychologist at the Memory and Aging Center at the University of California, San Francisco (UCSF). As we encounter novel information, our brains release chemicals that subtly alter our synapses and change the organ's physical form by blazing new neural pathways. Such tweaks stop only with degenerative disease or death.