At Ghent University, Guy Vingerhoets, Ph.D., Celine Berckmoes, M.S., and Nathalie Stroobant, M.S., knew that the left brain is dominant for language, and the right brain is dominant for emotion. But what happens when the brain is faced with emotional language? To find out, the researchers used Transcranial Doppler Ultrasonography (ultrasound), an inexpensive, non-invasive and patient-friendly way to measure blood-flow velocity in the brain's left and right middle cerebral arteries -- an indicator of activity level because neurons, to work, need blood-borne glucose and oxygen.
The researchers asked 36 participants, hooked up to ultrasound monitors, to identify the emotion conveyed in dozens of pre-recorded sentences. Vingerhoets et al. asked participants either to focus on the actual words (semantics) of the sentences, or to focus on the emotion conveyed by how they were spoken, in tone and intensity (prosody).
Each sentences had just one of four basic emotional meanings (happy, sad, angry or afraid) or a neutral semantic meaning. For example, "He really enjoys that funny cartoon" (happy), "The little girl lost both her parents" (sad), "Panic broke out in that dark tunnel" (fear), or "Always store disc in its protective case" (neutral). Actors spoke the sentences with either emotional or neutral prosody.
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 (because body movement on one side is controlled by the brain's opposite side). Vingerhoets et al. found that when participants were asked to focus on what was said -- semantics -- blood flow velocity went up significantly on the left side of the brain. When participants shifted attention to how it was said -- tone of voice, whether happy, sad, anxious, angry or neutral -- velocity also went up markedly on the right side of the brain. However, it did not go down on the left -- probably, say the researchers, because the left brain processes meaningful semantic content automatically and is also helps to label the emotions.
Thus, physical evidence has revealed that the right hemisphere, while indeed the brain's more "emotional" side, is not solely responsible for processing the expression of emotions. "Understanding emotional prosody," says Vingerhoets, "appears to activate right hemispheric brain regions." However, the left brain stays active to categorize or label the emotion -- as befits its dominance in language processing. "Even if you pay attention to the 'how' information," says Vingerhoets, "you can't help hearing the semantic content, the 'what' of the message. We do this all the time; we are trained in it."
Turning to clinical implications, Vingerhoets says, "People with right hemispheric lesions would have more difficulty paying attention to and discriminating emotional prosody."
Article: "Cerebral Hemodynamics During Discrimination of Prosodic and Semantic Emotion in Speech Studied by Transcranial Doppler Ultrasonography," Guy Vingerhoets, Ph.D.; Celine Berckmoes, M.S.; and Nathalie Stroobant, M.S., Ghent University; Neuropsychology, Vol. 17, No. 1.
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Guy Vingerhoets can be reached at the Laboratory for Neuropsychology, Ghent University, at email@example.com or by phone at 011-32-9-240-4587.
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