HAMILTON: In one sense, we've had to pay a heavy cost for our big, inefficient brains: childbirth is difficult, childhood is long, our brains consume 20 percent of the calories we eat. But Linden says these adaptations
turn out to have some surprising payoffs, like romantic love.
Mr. LINDEN: If our neurons weren't such lousy processors and we didn't need 100 billion of them massively interconnected in order to make a clever brain out of such lousy parts, then we wouldn't have such a long childhood while that brain grew up and matured after birth, and it wouldn't drive the dominant human
mating system - we wouldn't have love.
"Although the things it can do are very wonderful and impressive, its design is very poor engineering in many respects," says David Linden, a professor of
neuroscience at Johns Hopkins University in Baltimore, the author of The Accidental Mind.
"In evolution, you never build something new if you can adapt something you've already got," he says. "It's the ultimate tinkerer and the ultimate cheapskate."
Our brain has been put together with parts from jellyfish and lizards and mice, Linden says. These parts may have been OK for their original owners, he says, but they aren't ideal for us.
Take brain cells, for example."They are slow. They are inefficient. They leak signals to their neighbors,"
Linden says. "Consequently, if you want to build clever human us with these very suboptimal parts, the only way to do it is to build a brain that is simply enormous and massively interconnected."
And that means it's very slow. Linden says getting a simple message from our feet to our brain can take a remarkably long time. To get a sense of just how long, he says, imagine a giant with her head in Baltimore and her toe off the
coast of South Africa. If a shark bit that toe on Monday, Linden says, "she wouldn't feel it until Wednesday, and she wouldn't jerk her toe until Saturday."
Why the lag? Linden says it's because we're still using a communication system developed 600 million years ago by jellyfish."It's like adding scoops to an ice cream cone," Linden says. "So if you imagine the lizard brain as a single-scoop ice cream cone, the way you make a mouse brain out of a lizard brain isn't to throw the cone and the first scoop away and start over and make a banana split — rather, it's to put a second scoop on top of the first scoop."
"If our neurons weren't such lousy processors and we didn't need 100 billion of them massively interconnected in order to make a clever brain out of such lousy parts, then we wouldn't have such a long childhood," Linden says.
The Accidental Mind’ (Questions with author David Linden) American Physiological Society
1) What is one of the fundamental misunderstandings of the human brain according to Dr. Linden?
Answer: Historically in the lay public, the brain is represented as an elegantly designed organ. Dr. Linden believes that the brain is not elegantly designed or well-engineered, but cobbled together by evolution.
2) What is the analogy with a multi-scoop ice cream cone used in the book?
Answer: As the brain evolved from frog to mice to chimpanzee to human, the brain has become larger and larger, but there has been no re-design. The additional functions acquired during evolution have been added on just like a multi-scoop ice cream cone.
Answer: Additional evolutionary functions are added on to the brain like an ice cream cone. What this mean is that human beings have duplicate and often inefficient systems. For instance, human beings have in their brain a very
ancient, inefficient visual system that they share with reptiles and amphibians as well as a modern visual system that they share with mammals. Teacher Note: To demonstrate this, Lawrence Weiskrantz and colleagues from Oxford
were able to demonstrate the concept of "blindsight," an unusual condition where the sufferer can respond to visual stimuli, while lacking any conscious feeling of having seen the stimuli. In patients who were blind due to injury to the modern visual system in the brain (in the occipital lobe), the investigators were able to demonstrate that their ancient evolutionary visual system remained intact and was able to guide the patients to perform a basic visual task
although the patients had no perception of it. The ancient visual system is good for orientating human eyes and heads to moving targets.
4) Where is memory stored in the human brain?
Answer: Memory is initially stored in the hippocampus and surrounding tissues for a year or two. And then, memory is exported to other structures. For example, patients who have damage to their hippocampus lose memory for one to two years prior to the time of injury, but not earlier. In addition, memory is multi-sensory (visual, auditory, etc.). From the hippocampus, memory is broken apart and is exported and stored piecemeal to individual sensory regions of the brain. For example, visual memories are stored in the visual regions of the brain and auditory memories in auditory regions of the brain.