By ROBERT SAPOLSKY - THE NEW YORK TIMES
Added: Tue, 16 Nov 2010 15:00:54 UTC

Thanks to Laurie Fraser for the link

Despite rumors to the contrary, there are many ways in which the human brain isn’t all that fancy. Let’s compare it to the nervous system of a fruit fly. Both are made up of cells, of course, with neurons playing particularly important roles. Now one might expect that a neuron from a human will differ dramatically from one from a fly. Maybe the human’s will have especially ornate ways of communicating with other neurons, making use of unique “neurotransmitter” messengers. Maybe compared to the lowly fly neuron, human neurons are bigger, more complex, in some way can run faster and jump higher.

But no. Look at neurons from the two species under a microscope and they look the same. They have the same electrical properties, many of the same neurotransmitters, the same protein channels that allow ions to flow in and out, as well as a remarkably high number of genes in common. Neurons are the same basic building blocks in both species.

So where’s the difference? It’s numbers — humans have roughly one million neurons for each one in a fly. And out of a human’s 100 billion neurons emerge some pretty remarkable things. With enough quantity, you generate quality.

Neuroscientists understand the structural bases of some of these qualities. Take language, that uniquely human behavior. Underlining it are structures unique to the human brain — regions like “Broca’s area,” which specializes in language production. Then there’s the brain’s “extrapyramidal system,” which is involved in fine motor control. The complexity of the human version allows us to do something that, say, a polar bear, could never accomplish — sufficiently independent movement of digits to play a trill on the piano, for instance. Particularly striking is the human frontal cortex. While occurring in all mammals, the human version is proportionately bigger and denser in its wiring. And what is the frontal cortex good for? Emotional regulation, gratification postponement, executive decision-making, long-term planning. We study hard in high school to get admitted to a top college to get into grad school to get a good job to get into the nursing home of our choice. Gophers don’t do that.

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TAGGED: BEHAVIOR, BIOLOGY, PSYCHOLOGY