Human amygdalar activation has been reported during facial emotion recognition (FER) studies, mostly using fast temporal resolution techniques (fMRI, H215O PET or MEG). The 18FDG PET technique has never been previously applied to FER studies. We decided to test whether amygdala response during FER tasks could be assessed with this technique. The study was conducted in 10 healthy right-handed volunteers who underwent two scans on different days in random order. Content of the tasks was either emotional (ET) or neutral (CT) and lasted for 17 ½ min. Three SPM2 analyses were completed. The first, an ET-CT contrast, showed left amygdalar activation. The second ruled out order effect as a confounder factor. Finally, the whole brain contrast showed activation of the emotional recognition-related areas. Time responses and errors indicated high rates of accuracy in both tasks. We discuss the results and the role of habituation phenomena and the possibility of applying this technique to samples of patients with psychiatric disorders. In conclusion, our study reveals left amygdalar activation assessed with FDG PET, as well as other major emotion recognition-related brain areas during FER tasks.
The functional neuroimaging era has seen the progressive inclusion of different activation paradigms in the emotional perception circuit (Reiman et al., 1997, Zald and Prado, 1997, Buchanan et al., 2000 and Zalla et al., 2000), and helped to define the brain structures that play a role in the neurobiology of emotion. These brain areas include the amygdala, hippocampus, insula, anterior cingulate cortex, ventral striatum and orbitofrontal cortex (Dolan, 2002, Gur et al., 2002b, Phillips et al., 2003a and Calder and Young, 2005), as well as other areas that play more minor roles. A summary of the activation paradigms published reveals a general consensus that facial emotion recognition (FER) tasks act as the most powerful trigger for activation of the emotion network (Hariri et al., 2002). Some studies have also focused on which brain structure shows the greatest activation during FER paradigms, and the amygdala has been identified (Gur et al., 2002b and Williams et al., 2004). Indeed, during recent years, several studies have limited their analysis of FER effects to the amygdala (Fitzgerald et al., 2006), although reliance on a region of interest (ROI) approach in neuroimaging studies remains controversial (Friston et al., 2006 and Saxe et al., 2006).
