Right hemisphere cells process emotions - Brain - prefrontal cortex research - Brief Article

USA Today (Society for the Advancement of Education), Oct, 2002

A region at the front of the brain's right hemisphere, the prefrontal cortex, plays a critical role in how the human brain processes emotions. Data from previous studies of brain lesions (areas of damage that alter the brain's ability to generate normal emotions) and data from functional brain imaging studies have delineated the extent of the area involved. However, a University of Iowa, Iowa City, study is the first to investigate human emotion processing by the right prefrontal cortex at the level of individual brain cells.

A rare surgical situation allowed the researchers to record the activity of individual brain cells (neurons) in an awake, alert patient as he was shown images designed to elicit an emotional response. The patient was undergoing neurosurgery to treat epilepsy, which had not responded well to medication. Usually, electroencephalogram (EEG) electrodes placed on the scalp would be used to pinpoint where in the brain the epileptic seizures are localized. In this case, though, that approach did not work, so for treatment purposes the surgeon implanted depth electrodes into the patient's brain to monitor where the seizures originated.

Monitoring single neurons within the right prefrontal cortex, the researchers found that these cells responded remarkably rapidly to unpleasant images, including pictures of mutilations and scenes of war. Happy or neutral pictures did not cause the same rapid response from the neurons.

"The changes in firing patterns of neurons responding to the aversive visual stimuli happened within about 0.12 seconds, which is very fast and probably prior to the patient consciously `seeing' the image," explains Ralph Adolphs, assistant professor of neurology. "The speed at which these cells change their firing rates is surprisingly rapid. We thought it would take much longer for these neurons to be able to extract information about an emotion category, which is really a very high-level cognitive function.

"The area of the brain that we recorded from, the prefrontal cortex, is only one component of a widely distributed neural system for encoding this information. We think that another part of that information is encoded in visual cortices. The visual cortices would respond when the stimulus is seen, then those responses would be changed by subsequent input from the prefrontal cortex."