fMRI of the emotions: Towards an improved understanding of amygdala function

The last eight years have seen a rapid expansion in the number of functional Magnetic Resonance Imaging (fMRI) studies of the emotions, examining the role of the amygdala in healthy human emotion function as well as in psychiatric and neurological disorders such as depression, autism, anxiety disorders and schizophrenia. Amongst widely divergent results, the central findings of these studies are reviewed, as well as the most important unresolved questions. The location of central elements of the limbic system, of which the amygdala is a part, makes it a challenging area to study with fMRI. The problems besetting the region are reviewed: signal loss and image distortion in Echo Planar Imaging and artefacts arising from physiological fluctuations, head motion and draining veins. We describe general approaches to mitigating these problems and which of those we find to be most useful. An illustrative example from our lab is presented to indicate the typical progression of an emotion fMRI session and to allow discussion of the strategies employed which enable robust amygdala function to be charted in single subjects and groups. We conclude by examining the prospects for technical improvement and clinical applications.