1. Wrinkles make us smart
What’s the secret to our species’ smarts? The answer may be wrinkles. The surface of the human brain is convoluted by deep fissures, smaller grooves called sulci, and ridges called gyri. This surface is called the cerebral cortex and is home to about 100 billion neurons, or nerve cells.
The folded, meandering surface allows the brain to pack in more surface area — and thus, more processing power — into the limited confines of the skull. Our primate relatives show varying degrees of convolution in their brains, as do other intelligent creatures like elephants. In fact, research done by Emory University neuroscientist Lori Marino has found that dolphins have even more pronounced brain wrinkles than humans.
2. Most of our brain cells aren’t neurons
The old saw that we use just 10 percent of our brainpower isn’t true, but we now know that neurons make up just 10 percent of our brain cells.
The other 90 percent, which account for about half the brain’s weight, are called glia, which means “glue” in Greek. Neuroscientists used to think glia were simply the sticky stuff that holds neurons together. But recent research has shown glia to be much more. A 2005 paper in the journal Current Opinions in Neurobiology laid out the roles of these unsung cells, which range from mopping up excess neurotransmitters to providing immune protection to actually promoting and modulating synapse growth and function. (Synapses are the connections between neurons.) It turns out the silent majority isn’t so silent after all.
3. The brain is an exclusive club
Like bouncers at a night club, an assembly of cells in the brain’s blood system, called the blood-brain barrier, lets only a few molecules into the nervous system’s inner sanctum – the brain. The capillaries that feed the brain are lined with tightly bound cells, which keep out large molecules. Special proteins in the barrier transport necessary nutrients and substances into the brain. Only an elite few make it through.
The blood-brain barrier protects the brain, but it can also keep out lifesaving medications. Physicians trying to treat brain tumors can use drugs to open the junctions between cells, but that leaves the brain temporarily vulnerable to infection. One new way to sneak meds past the barrier might be nanotechnology. A 2009 study published in the journal Cancer Research showed that specially-engineered nanoparticles can cross the barrier and attach to tumor tissue. In the future, combining nanoparticles with chemotherapy drugs could be one way to target tumors.
4. The brain starts as a tube
The foundation for the brain is set early. Three weeks after conception, a sheet of embryonic cells called the neural plate folds and fuses into the neural tube. This tissue will become the central nervous system. The neural tube grows and differentiates throughout the first trimester. (When cells differentiate they specialize into various tissues needed to create body parts.) It isn’t until the second trimester that glia and neurons begin to form. The brain doesn’t wrinkle up until even later. At 24 weeks, magnetic resonance imaging shows just a few nascent grooves in the otherwise smooth surface of the fetal brain, according to a 2000 study in the journal Radiology. As the third trimester begins in week 26, the grooves deepen and the brain begins to look more like that of a newborn.
5. Teen brains aren’t fully formed
Parents of stubborn teenagers rejoice, or at least relax: That adolescent attitude stems, in part, from the vagaries of brain development. The gray matter of the brain peaks just before puberty and is pruned back down throughout adolescence, with some of the most dramatic development happening in the frontal lobes, the seat of judgment and decision-making.
A 2005 study published in the journal Child Development found that the parts of the brain responsible for multitasking don’t fully mature until we’re 16 or 17 years old. And research presented at the BA Festival of Science in 2006 revealed that teens also have a neural excuse for self-centeredness. When considering an action that would affect others, teens were less likely than adults to use the medial prefrontal cortex, an area associated with empathy and guilt. Teens learn empathy by practicing socializing, the researchers said. So much for grounding them until they’re 20.