Frontal asymmetry in emotion, personality and psychopathology: Methodological issues in electrocortical and hemodynamic neuroimaging

Introduction It is well established that depression and anxiety are associated with abnormal patterns of asymmetric brain activity, particularly in frontal regions (Heller et al.,1998). Data in support of this finding have highlighted the relative roles of left and right frontal regions in positive and negative emotions, respectively (Davidson & Irwin, 1999). In recent years it has become increasingly clear that asymmetric brain function can be understood not only in terms of theories of emotion, but also in terms of specific personality constructs. Despite decades of EEG research identifying frontal asymmetries in emotion and personality, these findings have been largely unreplicated by hemodynamic studies (e.g. functional MRI and PET). This chapter will briefly review evidence regarding the contribution of frontal brain asymmetries to understanding components of emotion, motivation and personality. The review will be followed by a more detailed consideration of how frontal brain asymmetries can and should be measured using hemodynamic imaging. Examples of recent studies from our laboratories that illustrate some of the methodologies discussed will also be presented (Herrington et al., 2005; Herrington et al., under review; Nitschke et al., 2006).