SAN DIEGO, CALIFORNIA—How do we recognize emotions in the facial expressions of others? A small, almond-shaped structure called the amygdala, located deep within the brain (yellow in image above), plays a key role, but exactly what it responds to is unclear. To learn more, neuroscientists implanted electrodes into the amygdalae of seven epileptic patients who were about to undergo brain surgery for their condition. They recorded the activity of 200 single amygdala neurons and determined how they responded while the patients viewed photographs of happy and fearful faces. The team found a subset of cells that distinguish between what the patients thought to be happy and fearful faces, even when they perceived ambiguous facial expressions incorrectly. (The team carefully manipulated some of the photos of fearful faces, so that some of the subjects perceived them as being neutral.) The findings, presented here yesterday at the 43rd annual meeting of the Society for Neuroscience, suggest that amygdala neurons respond to the subjective judgement of emotions in facial expressions, rather than the visual characteristics of faces that convey emotions. The scientists also found that the cellular responses persisted long after each of the photographs disappeared, further suggesting that the amygdala cooperates with other brain regions to create awareness of the emotional content of faces. Thus, when it comes to recognizing the facial expressions of others, what we think we see seems to be more important than what we actually see.
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