Word: braine
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Dates: during 1990-1999
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Within explicit, or declarative, memory, on the other hand, there are specific subsystems that handle shapes, textures, sounds, faces, names--even distinct systems to remember nouns vs. verbs. All of these different types of memory are ultimately stored in the brain's cortex, within its deeply furrowed outer layer--a component of the brain dauntingly more complex than comparable parts in lesser species. Experts in brain imaging are only beginning to understand what goes where, and how the parts are reassembled into a coherent whole...
What seems to be a single memory is actually a complex construction. Think of a hammer, and your brain hurriedly retrieves the tool's name, its appearance, its function, its heft and the sound of its clang, each extracted from a different region of the brain. Fail to connect a person's name with his or her face, and you experience the breakdown of that assembly process that many of us begin to experience in our 20s--and that becomes downright worrisome when we reach...
...altered mice grow up looking and acting just like ordinary mice, with no evidence of seizures or convulsions, according to Tsien. That's critical. The NMDA receptor shows up throughout the brain, and though calcium is crucial to learning and memory, too much of it can lead to cell death. That's what happens during a stroke: when brain cells are deprived of oxygen, they release huge amounts of glutamate, which overstimulates nearby NMDA receptors and kills their host cells. Nature may have designed NR2B-based receptors to taper off in adult brains for a reason. Some scientists fear that...
Premature cell death isn't the only possible complication. Stanford's Robert Malenka has shown that the NMDA receptor is involved in sensitizing the brain to drugs like cocaine, heroin and amphetamines, and others are investigating its role in triggering chronic pain--two more indications that it may not be wise to try to fool Mother Nature...
...Tsien doesn't claim that he and his colleagues have found the unique genetic key to intelligence or even to memory. "It's likely that brain plasticity involves many molecules," he says. "This is just one of them." On the other hand, he asserts--and his critics would not disagree--that "intelligence does arise out of biology, at least in part." How much remains the great question. Whatever the answer, little Doogie surely represents an important step in unraveling what role our genes play in constructing not just memory but all the other attributes of the human mind. And clearly...