We tend to spontaneously focus on the eyes and mouth when we scan a face: a smile reveals happiness, whereas a furrowed brow might indicate anger. Some people with autism cannot easily understand these facial expressions, however. Ralph Adolphs and his colleagues at the California Institute of Technology study how people with autism interpret and respond to cues from human faces. Two regions of the brain that have roles in interpreting facial expressions - the amygdala and the corpus callosum - are frequently dysfunctional in autism. The amygdala integrates sensory inputs with memories to evaluate the meaning of a facial expression. The corpus callosum contains the connections of many neurons between one side of the brain and the other, which are necessary for complex neurological processes. In a recent project for SFARI, Adolphs and his colleagues compared people with autism with those who have lesions in the amygdala or the corpus callosum. The researchers found several similarities between the two groups: they all have impairments in social functioning and difficulty recognizing emotions from faces, and make abnormal eye fixations onto faces. The researchers anticipate heterogeneity in the involvement of these two brain structures in people with autism. For example, some might have poor connectivity in the corpus callosum, whereas others could have abnormal activity in the amygdala, and some might have neither. These differences could help researchers identify and understand subtypes of autism spectrum disorders. In a unique and exciting extension of these studies, Adolphs and his colleagues propose to record electrical signals directly from amygdala cells in rare neurosurgical patients who have electrodes implanted in their brain for monitoring epilepsy, which is frequently seen in people with autism. The researchers have recorded neuronal activity from the amygdala in two people with autism and epilepsy, as well as in several people who have epilepsy but not autism. Comparisons of how amygdala neurons respond to face stimuli in people with autism may provide finely detailed information about how the amygdala contributes to social functioning, and how abnormal responses within it contribute to autism.