Researchers discover brain hate circuit
Are love and hate poles apart when brain activity is involved? A team of scientists from University College London (UCL) in the UK think not. Their research, published recently in the journal PLoS One, shows that while hate is characterised by a unique pattern of activity in the brain, love and hate share two common structures.
Having already studied the brain mechanisms of romantic and maternal love, in this study the researchers focused on the emotion of hate directed against a person such as a work colleague or ex-lover. The sample consisted of 17 subjects (10 male and 7 female, 12 right-handed with a mean age of 34.8 years).
Led by Professor Semir Zeki and John Romaya of the Wellcome Laboratory of Neurobiology at UCL, the scientists investigated the areas of the brain that correlate with the emotion of hate. The 'hate circuit' differs from those areas linked to danger or fear, but it shares the brain area linked to aggression.
The brains of the 17 subjects were scanned while they were looking at pictures of their hated persons and those of neutral faces belonging to people they were familiar with.
The research team said that both the putamen (the outer, reddish part of the lenticular nucleus that is connected to the perception of contempt and disgust) and the insula (insular cortex) kicked in when the subjects were shown pictures of people they hate. This connection may be the reason why love and hate are so closely linked to each other, the authors suggest in their paper.
'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,' remarked Professor Zeki. 'Previous studies have suggested that the insula may be involved in responses to distressing stimuli, and the viewing of both a loved and a hated face may constitute such a distressing signal.'
Professor Zeki said the difference between the emotions of love and hate is that large parts of the cerebral cortex become deactivated with love, but only a small part becomes deactivated with hate. 'This may seem surprising since hate can also be an all-consuming passion, just like love,' he said. 'But whereas in romantic love, the lover is often less critical and judgemental regarding the loved person, it is more likely that in the context of hate, the hater may want to exercise judgement in calculating moves to harm, injure or otherwise extract revenge.'
Structures in the cortex and in the sub-cortex are included in the 'hate circuit'. According to the researchers, they have components that fuel aggressive behaviour, and then translate this into action through motor planning. This can be described as the brain becoming mobilised to take action. The frontal cortex is also involved in guessing the actions of others. This may be helpful for people when they come face to face with someone they hate.
'Hate is often considered to be an evil passion that should, in a better world, be tamed, controlled and eradicated,' commented Professor Zeki. '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,' he said. 'How can two opposite sentiments lead to the same behaviour?'
The UCL researcher noted that while romantic love is directed at one individual, 'hate can be directed against entire individuals or groups, as is the case with racial, political or gender hatred'. Professor Zeki said he expects to launch studies into the different varieties of hate in the future.