WEDNESDAY, Oct. 29, 2008 (HealthDay News) -- British researchers say they've identified a "hate circuit" in the brain.
This hate circuit shares part of the brain associated with aggression, but is distinct from areas related to emotions such as fear, threat, and danger, said researchers Professor Semir Zeki and John Romaya, of University College London's laboratory of neurobiology.
The study was published online Oct. 29 in the journal PLoS One.
"Hate is often considered to be an evil passion that should, in a better world, be tamed, controlled, and eradicated," Zeki said in a journal news release. "Yet to the biologist, hate is a passion that is of equal interest to love. Like love, it is often seemingly irrational and can lead individuals to heroic and evil deeds. How can two opposite sentiments lead to the same behavior?"
In this study, 17 female and male volunteers underwent brain scans while they looked at photos of a person they hated, along with photos of a "neutral" person. Looking at images of hated people triggered activity in an area that includes structures in the cortex and in the sub-cortex as well as components that generate aggressive behavior and translate it into action.
The hate circuit also includes a part of the frontal cortex that's believed to play a major role in predicting the actions of others, likely an important feature when a person is faced with someone they hate, the researchers said.
The sub-cortical activity of the hate circuit involves two structures called the putamen and insula. The putamen plays a role in the perception of contempt and disgust, and may be part of the motor system that's mobilized to take action, the scientists said.
"Significantly, the putamen and insula are also both activated by romantic love. This is not surprising. The putamen could also be involved in the preparation of aggressive acts in a romantic context, as in situations when a rival presents a danger. Previous studies have suggested that the insula may be involved in responses to distressing stimuli, and the viewing of both a loved one and a hated face may contribute such a distressing signal," Zeki said.
He added that activity in parts of the hate circuit matches the strength of the person's declared intensity of hate, "thus allowing the subjective state of hate to be objectively quantified. This finding may have legal implications in criminal cases, for example."
The Science Museum in London, England, has more about the brain and emotions.