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 Monday, 13 January, 2003, 00:08 GMT
How the brain processes emotions
Emotions trigger increased blood flow to the brain
Scientists have discovered how the brain processes emotionally charged information.

They have found that the left side of the brain alone appears to take responsibility for decoding the literal meaning of emotional messages.

But it seems that the brain's right hemisphere plays a role in assessing the tone in which the message is delivered - a concept known technically as prosody.

The findings are based on measuring how fast blood flows to the tissues of the brain.

A greater velocity implies more activity in that area of the brain because brain cells, when active, require an increased supply of oxygen and glucose, both of which are carried in the blood.

A team from Ghent University in Belgium used a technique called transcranial doppler ultrasonography to measure blood flow velocity in the brain's left and right middle cerebral arteries.

Meaning and tone

Sample sentences
He really enjoys that funny cartoon (happy)
The little girl lost both her parents (sad)
Panic broke out in that dark tunnel (fear)
Always store disc in its protective case(neutral)
The researchers asked 36 participants, hooked up to ultrasound monitors, to identify the emotion conveyed in dozens of pre-recorded sentences.

The volunteers were asked either to focus on the actual meaning of the words, or on the emotion conveyed by how they were spoken.

Each sentences had just one of four basic emotional meanings (happy, sad, angry or afraid) or was neutral (see box).

Actors spoke the sentences with either an emotional or neutral tone.

As they listened to the sentences, participants pointed to the appropriate emotion on a card listing them, using both fingers to minimize setting off one side of the brain only.

Blood flow

The researchers found that when participants were asked to focus on the meaning of what was said blood flow velocity went up significantly on the left side of the brain.

But when attention was shifted to how to how it was said velocity also went up markedly on the right side of the brain.

However, it did not go down on the left - suggesting that both sides of the brain play a role in helping to label the emotions.

Lead researcher Professor Guy Vingerhoets told BBC News Online: "It appears that we have a different pattern of cerebral activity devoted to the emotional 'what' and the emotional 'how' of the spoken message.

"Our findings suggest patients with right hemispheric lesions could experience more problems in understanding the emotional prosody of a spoken message and certainly may have difficulties in correctly discriminating deliberate discrepancies in content and prosody that convey more subtle forms of emotional expression in speech."

Accident victims

Psychologist David Zald, of Vanderbilt University in Nashville, has carried out similar research into the functioning of the brain.

He told BBC News Online previous research had suggested that people who had suffered injury to the right side of their brains had trouble making sense of emotional information.

However, he said the technique used in the study was limited because it could not show which specific areas of the brain within each hemisphere were active at any given time.

Professor Tonmoy Sharma, director of the Clinical Neuroscience Research Centre, Dartford, Kent, said the technique used in the study had great potential as a tool for investigating the effects of brain injury.

"It is cheap to use, and completely non-invasive," he said.

The research is published in Neuropsychology, the journal of the American Psychological Association.

See also:

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