| Research
suggesting that perception of emotions is localized to specific regions
may give clues to abnormalities seen with schizophrenia Magnetic resonance imaging of people looking at test pictures suggests that perception of emotions such as disgust is localized to specific brain regions, according to an article published February 14th in the online issue of Annals of Neurology. Findings from this and other studies may have important implications for understanding the neurobiology of disorders including schizophrenia and dementia. Previous studies that took magnetic resonance imaging scans of subjects looking at pictures of faces showing fear, happiness, disgust and other emotions have indicated that different regions in the brain become active in response to different expressions. These recent studies have largely supported older findings from patients with damage to isolated regions of the brain from stroke or trauma. For instance, it is well known that people with damage to the amygdala find it difficult to understand the facial expression of fear in other people, although they are able to identify other emotions such as happiness and sadness. It is interesting that the amygdala is also involved in the sensation of internal fear; this suggests that it may coordinate both the experience of fear and the recognition of fear in others. Recently, researchers have identified the insula as being important for the recognition of disgust in other people's faces. This is partly a result of studying patients with Huntington's disease, which damages neurons in the insula and related areas. Huntington's patients have particular trouble recognizing facial expressions of disgust. In the current study, French researchers applied precise mapping tools to the question of how the brain processes disgust. They studied epilepsy patients who had been implanted with electrodes in preparation for possible surgery. When the subjects viewed pictures of faces showing disgust, scans showed that neurons in very specific subregions of the insula became active. Neurons in other parts of the insula or surrounding brain areas did not respond in this way. On the other hand, the areas that became activated in response to disgust did not respond to happiness, fear, or neutral expressions. The researchers also noted that the insula did not respond as quickly to the pictures as did other areas that respond to facial expressions. This finding supports the idea that the insula plays a more complicated role in integrating recognition of disgust. "This is the first time that data specify where and when the insula participates in the recognition of disgust. And we know that this part of the insula is connected to areas of the brain involved in taste, smell, and control of the visceral organs," said lead author Pierre Krolak-Salmon, M.D. The authors stressed that the insula is probably not the single center for disgust processing. Instead, it is likely to be an integral part of a larger network that processes disgust and perhaps other emotions. It may be involved in both the experience of disgust and the recognition of disgust in others. "Facial expression recognition is impaired
in schizophrenia, some types of dementia, Huntington's disease and
others. This deficit may interfere with social contact and communication
in these patients, which is why it's very important to define which
neural networks are implicated in the processing of facial expressions,"
said Krolak-Salmon. |