Saturday, May 15, 2004
The second article in The April 2004 issue of CNS Spectrums is titled Recognition of Facial Emotions in Neuropsychiatric Disorders. It was written by Christian G. Kohler, MD, Travis H. Turner, BS, Raquel E. Gur, MD, PhD, and Ruben C. Gur, PhD. Most of them are from the University of Pennsylvania. I'm not sure why this article is in with the others, since it is not really about neuroimaging. The abstract is here:
Recognition of facial emotions represents an important
aspect of interpersonal communication and is governed
by select neural substrates. We present data on emotion
recognition in healthy young adults utilizing a novel set
of color photographs of evoked universal emotions.
In addition, we review the recent literature on emotion
recognition in psychiatric and neurologic disorders, and
studies that compare different disorders.
CNS Spectr. 2004;9(4):267-274
The authors claim that certain facial expression of emotion are universal; others are subject to variation from one culture to the next. The universal ones are: happiness, anger, fear, sadness, and disgust. Variable expressions include shame, arrogance, contempt, guilt, flirtatiousness, and admiration. [Editorial note: travelers are advised to remember that flirting is not recognized universally.] They report that the classical hypothesis is that much of the processing that our brains go through to interpret facial expressions takes place in the right hemisphere. Some researchers believe that the right hemisphere is best at interpreting all kinds of emotional expressions. Others feel that the left hemisphere is used more in the interpretation of positive feelings; the right being better at processing negative feelings. The authors report that they conducted a meta-analysis of 65 pertinent neuroimaging studies, and that support for these notions of lateralization is limited, but not absent.
The reason that the processing of facial cues of emotional expression is important is that problems in such processing occur in certain types of brain injury, developmental disorders, and in thought disorders, especially schizophrenia. In persons with no injury, developmental disorder, and with no thought disorder, the recognition of facial emotional expression is an important part of communication.
They report on the various methodologies used, and the limitations of earlier methods. Specifically, the use of greyscale versus color images, and the use of images of only Caucasians, introduce problems. They worked with a set of 96 images rendered in color, and in 3D, to try to overcome some of the limitations of earlier studies.
One of their earliest findings was that the amygdala is activated in tasks of recognition of facial emotional expressions, and that this activation is muted in persons with schizophrenia. They go on to report on the accuracy of recognition in normal subjects, then review various pathological states, including schizophrenia, mood disorders, brian injury, neurodegenerative diseases, autism, and mental retardation.
Among normal subjects, happiness is the expression that is recognized most precisely, followed by fear, sadness, anger, and disgust. With all of these emotions except disgust, error rates are lower when the pictures illustrate emotions expressed with greater intensity.
With regard to schizophrenia, they point out that impairment of the capacity to identify accurately the various expression of emotion is mentioned in even the earliest case reports. It is considered to be a significant source of social impairment. This appears to be true, independent of the effects of other kinds of symptoms (hallucinations, delusions, and cognitive impairments.) They report that the difficulty in persons with schizophrenia is at least partly localized to the mesial temporal regions of the brain. The difficulty occurs both with regard to correct identification of emotional expression, and with regard to incorrect attribute of emotion when the stimulus is a picture of a neutral expression. Also, persons with schizophrenia did not achieve greater precision when the intensity of the expressed emotion increased. the authors do not speculate as to why this latter finding would occur. However, it has been recognized for a long time that persons with schizophrenia are more prone to have problems with symptoms when they are in the presence of others who are engaging in intense expressions of emotion. It is as though the more intense expressed feelings somehow provoke greater interference with cognitive processing. It is tempting to hypothesize that the emotional interference with cognition is responsible for their finding, that persons with schizophrenia do not attain greater precision when asked to identify stronger expression of emotion. I would like to see a study that uses functional neuroimaging to test this hypothesis.
With regard to bipolar disorder, the authors report on studies with stable bipolar patients, meaning that they were neither manic nor depressed at the time of the study. These persons had difficulty accurately rating the intensity, but not the quality, of emotional expressions. By this they mean that patients with bipolar disorder can accurately identify what kind of emotion they are seeing, but not how intense the expression is. In contrast, persons who are actively manic at the time of the study have greater difficulty recognizing negative expressions. This is consistent with other observations, that persons who are manic tend to see everything in a positive light.
Turning their attention to major depression, they note that there have not been very many studies. Perhaps this is because the studies that have been done so far are not very interesting. At least one study showed a negative bias, indicating that people who are depressed are more likely to view others as being depressed.
Next to be considered was the topic of developmental disorders. This would include mental retardation and autism. There is a bit of a controversy about whether persons with mental retardation have a separate impairment of their ability to recognize emotions, or whether their difficulties are due to a general cognitive impairment. Review of the studies shows scant evidence for a selective impairment. Even among those with autism, there is no particular evidence for a selective impairment. Any difficulties experienced by persons with autism were correlated with general intelligence.
The authors then considered the effect of brain lesions. The start by mentioning Urbach-Wiethe disease. (Yeah, I had to look it up, too. Link-free registration required) This is a disease that, among other things, causes selective destruction of the amydgala. As expected, such persons have impaired ability to recognize expressions of fear; sometimes, recognition of other negative emotions is impaired as well. Studies on persons who have had a stroke indicate that a loss of right hemisphere tissue have greater impairment of recognition of facial expression of emotion than those with lesions on the left.
Alzheimer's Disease tends to cause early loss of mesial temporal lobe structures, including the hippocampus and amydgala. This leads to impairment of recognition of facial expression of emotion, as expected. Persons with frontotemporal dementia tend to have even greater impairment. However, the frontotemporal dementia patients did have sparing of the ability to recognize fear.
Return to the Corpus Callosum, here.
(Note: The Rest of the Story/Corpus Callosum has moved. Visit the new site here.)
E-mail a link that points to this post: