Brain Damage Newsroom

Brain Damage Disrupts Emotions and Mood

Feeling tense and anxious? Unfettered and carefree? It may be all in your head or — rather — your cerebral hemispheres. According to scientists at the National Institute of Neurological Disorders and Stroke (NINDS), new research suggests that the brain's hemispheres generate our emotional outlook. Scientists also say their findings, announced today at the annual meeting of the American Academy of Neurology in San Diego, show that brain damage can change judgment of emotion and distort normal mood.

"Our findings give us new insight into how the brain's two hemispheres work together in a delicate balance to steady emotion and mood," says NINDS neuropsychologist Paul Fedio, Ph.D. "They also show how one-sided brain damage can disrupt this balance."

The cerebral hemispheres — those large, wrinkled, oval-shaped lobes that dominate any picture of the human brain — are responsible for most complex mental activities. The hemispheres tend to specialize, with specific cognitive functions controlled by one side. For example, the left hemisphere is responsible for language in most people, while the right hemisphere usually controls spatial skills, such as reading a map.

Normally, Dr. Fedio says, the brain's two hemispheres work in tandem to judge emotions around us so we can make the right response. "The right brain functions like radar, scanning for the blip on the screen — signs of negative emotion or danger — and alerts the left side. The left hemisphere analyzes the situation, determines the risk, and formulates logical strategy.

"But in our research," Dr. Fedio continues, "we found that with damage to the left brain, the right brain become overstimulated and runs out of control. The patient becomes anxious, pessimistic, and tense."

In the study, NINDS scientists played tapes of positive and negative emotional sounds, such as a baby cooing or a woman screaming, to 10 patients with lesions of the left hemisphere, 10 patients with right-hemisphere epilepsy, and 10 normal controls. They measured patients' brain activity using electroencephalography (a technique that uses scalp electrodes to measure the brain's electrical activity) and asked patients to describe what they heard. Left-hemisphere patients had relatively more right-brain activity.

Although all of the patients identified most sounds accurately, those with left-hemisphere lesions repeatedly described positive sounds in a negative context. "The left-brain patient says 'That's a baby cooing, maybe it's in danger, maybe it's calling its mother'," says Dr. Fedio. On the other hand, patients with right-brain epilepsy seemed understimulated and underconcerned, Dr. Fedio says. "They might hear the woman screaming but optimistically assume she was not in trouble. It's almost like both groups have an emotional dyslexia."

Dr. Fedio says the findings tie in with other perplexing observations that neurologists have made. "It makes it easier to understand why patients with left-brain stroke are at risk for suicide, since we've found that left-brain damage produces a negative outlook. It may also explain why right-brain stroke patients tend to check themselves out of the hospital early. These patients underestimate their disabilities and are overly optimistic. They think 'Yes, I can't walk and my left arm's paralyzed, but it'll get better. I don't need treatment'." In fact, Dr. Fedio says, such patients can refuse to acknowledge their problems and, as a result, resist treatment.