Brain Detects Happiness More Quickly Than Sadness

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ScienceDaily (June 21, 2009) — Our brains get a first impression of people's overriding social signals after seeing their faces for only 100 milliseconds (0.1 seconds). Whether this impression is correct, however, is another question. Now an international group of experts has carried out an in-depth study into how we process emotional expressions, looking at the pattern of cerebral asymmetry in the perception of positive and negative facial signals.

The researchers worked with 80 psychology students (65 women and 15 men) to analyze the differences between their cerebral hemispheres using the "divided visual field" technique, which is based on the anatomical properties of the visual system.
"What is new about this study is that working in this way ensures that the information is focused on one cerebral hemisphere or the other", J. Antonio Aznar-Casanova, one of the authors of the study and a researcher at the University of Barcelona (UB), tells SINC.
The results, published in the latest issue of the journal Laterality, show that the right hemisphere performs better in processing emotions. "However, this advantage appears to be more evident when it comes to processing happy and surprised faces than sad or frightened ones", the researcher points out.
"Positive expressions, or expressions of approach, are perceived more quickly and more precisely than negative, or withdrawal, ones. So happiness and surprise are processed faster than sadness and fear", explains Aznar-Casanova.
The two faces of the brain
This research study adds to previous ones, which had revealed asymmetries in the way the brain processes emotions, and enriches the international debate in cognitive-emotional neuroscience in terms of how to define the exact way in which human beings process these facial expressions.
People make deductions from the expressions on people's faces. "These inferences can strongly influence election results or the sentences given in trials, and have been studied before in fields such as criminology and the pseudoscience of physiognomy", the neuroscientist tells SINC.
Two theories are currently "competing" to explain the pattern of cerebral asymmetry in processing emotions. The older one postulates the dominance of the right hemisphere in the processing of emotions, while the second is based on the approach-withdrawal hypothesis, which holds that the pattern of cerebral asymmetry depends upon the emotion in question, in other words that each hemisphere is better at processing particular emotions (the right, withdrawal, and the left, approach).
"Today there is scientific evidence in favour of both these theories, but there is a certain consensus in favour of the lateralisation of emotional processing predicted by the approach-withdrawal hypothesis", concludes Aznar-Casanova.
Journal reference:
Alves et al. Patterns of brain asymmetry in the perception of positive and negative facial expressions. Laterality Asymmetries of Body Brain and Cognition, 2008; 14 (3): 256 DOI: 10.1080/13576500802362927
Adapted from materials provided by Plataforma SINC.

Needle Biopsies Safe In 'Eloquent' Areas Of Brain, Study Suggests

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ScienceDaily (June 5, 2009) — After a review of 284 cases, specialists at the Brain Tumor Center at the University of Cincinnati (UC) Neuroscience Institute have concluded that performing a stereotactic needle biopsy in an area of the brain associated with language or other important functions carries no greater risk than a similar biopsy in a less critical area of the brain.

The retrospective study, led by Christopher McPherson, MD, director of the division of surgical neuro-oncology at UC and a Mayfield Clinic neurosurgeon, was published online in May in the Journal of Neurosurgery.
The UC study compared the complication rates of stereotactic biopsies in functional, or “eloquent,” areas of the brain that were associated with language, vision, and mobility to areas that were not associated with critical functions. Eloquent areas included the brainstem, basal ganglia, corpus callosum, motor cortex, thalamus, and visual cortex. Complications were defined as the worsening of existing neurological deficits, seizures, brain hemorrhaging and death.
“Needle biopsies in eloquent areas have generally been acknowledged to be safe, because the needle causes only a small amount of disruption to the brain,” McPherson explains. “But until now, researchers had not actually documented that biopsies in eloquent areas were as safe as those in non-eloquent areas.”
To make that comparison, McPherson’s team studied records of 284 stereotactic needle biopsies performed by 19 Mayfield Clinic neurosurgeons between January 2000 and December 2006. In the 160 biopsies that involved eloquent areas of the brain, complications occurred in nine cases (5.6 percent of the total). In the 124 biopsies that involved non-eloquent areas, complications occurred in 10 cases (8.1 percent). The difference was not statistically significant.
Overall, 19 of the 284 patients, or 6.7 percent, suffered complications. Thirteen of those patients recovered completely or somewhat from their complications, while six (2.1 percent of the total number of patients biopsied) experienced permanent neurological decline.
“Diagnosing and treating brain tumors always carries risk,” McPherson says. “Within that context, the results of this large sampling of biopsies are encouraging overall and reinforce our belief that stereotactic biopsy is a valuable diagnostic tool. Stereotactic biopsy is a safe way for us to remove a tissue sample for the diagnosis of a brain tumor, even when the tumor is in a challenging and dangerous part of the brain.”
Additional co-authors of the study are Ronald Warnick, MD, director of the UC Brain Tumor Center and chairman of the Mayfield Clinic; James Leach, MD, associate professor of neuroradiology at UC and a neuroradiologist at Cincinnati Children’s Hospital Medical Center and the UC Neuroscience Institute; and Ellen Air, MD, PhD, a resident in the UC Department of Neurosurgery.
Journal reference:
Air et al. Comparing the risks of frameless stereotactic biopsy in eloquent and noneloquent regions of the brain: a retrospective review of 284 cases. Journal of Neurosurgery, 2009; 090501065138063 DOI: 10.3171/2009.3.JNS081695
Adapted from materials provided by University of Cincinnati Academic Health Center.