Can't Remember What's-His-Name? Blame it on Brain Hemisphericity

Photo of Michael Privitera, MD, by UC Academic Health Center Medical Communications

Most people are either right-brained or left-brained. What does that mean? And what about people who are whole-brained, with both sides equally strong? Do neurologists tend to be right-brained while surgeons tend to be left-brained? Michael Privitera, MD, Professor of Neurology and Director of the Epilepsy Center at the UC Neuroscience Institute, answers:

“When we talk about being left-brained or right-brained, what we’re typically talking about is language, because that’s the main thing in the brain that is lateralized, typically, to one hemisphere. In about 96 percent of right-handed people, language is located in the left hemisphere. Among left-handed people, about 80 percent are left-hemisphere dominant, which means they have a right-hander’s brain, and about 5 percent are right-hemisphere dominant, which means they have a true left-hander’s brain. Then there’s another group – more common among left-handers and very rare among right-handers – who have language on both sides.

"We find people who are bilateral, or whole-brained, more commonly among left-handers than right-handers.
 
"Many scientists are intrigued with functions of the non-language-dominant hemisphere, which is responsible for spatial-perceptual thinking. For example, your ability to understand language is part of the dominant hemisphere, but your ability to read a map and figure out where a place is on a map, which is a very spatial, perceptual skill, is part of the non-dominant side. Drawing a figure and gauging an angle of a line also come out of the right hemisphere. Artists have more spatial-perceptual skills than the average person. Music, for the most part, is a right-hemisphere, non-dominant-hemisphere function.

"In general, surgeons are attracted to doing right-hemisphere activities that involve perceptual and spatial skills, while neurologists and internists tend to be more verbal. They like written things, they like reading about things, explaining things.

"Memory also seems to be similarly lateralized. If we test somebody’s memory, we can test their retention of words or word lists or details of stories that you read or they read. But when we want to test the non-dominant hemisphere, we can test memory for people’s faces, pictures or drawings. If I show you a spoon, your brain will absorb the image of the spoon and file away that image in the right hemisphere. But it will remember the word “spoon” in the left hemisphere. So when you remember things, you usually encode them verbally and non-verbally. People who can’t express exactly why they know something – who say they have a gut feeling – have the information in their brain but can’t move that information over to the expressive language areas of their brain.

"When you see somebody and recognize that person but can’t think of the person’s name, you’re trying to use both sides of your brain: the image of the person’s face is in your right hemisphere and you know you’ve seen him before, but you can’t remember his name because the name is in the other hemisphere.

"These are simple examples, and most of the brain’s efforts involve the incorporation of speech, memory, emotion and judgment into complex networks. It is the complexity of these networks that makes our brains so difficult for a computer to model."