Hemispheric specialization for emotional word processing is a function of SSRI responsiveness Amy Walsh, John McDowall, Gina M. Grimshaw ⇑ Victoria University of Wellington, New Zealand article info Article history: Accepted 15 September 2010 Available online 12 October 2010 Keywords: Depression SSRI response Emotional words Hemispheric asymmetry Perceptual asymmetry Divided visual field abstract Vulnerability to depression and non-response to Selective Serotonin Reuptake Inhibitors (SSRIs) are asso- ciated with specific neurophysiological characteristics including greater right hemisphere (RH) relative to left hemisphere (LH) activity. The present study investigated the relationship between hemispheric spe- cialization and processing of emotional words using a divided visual field paradigm administered to never-depressed and previously-depressed individuals, who were subdivided into SSRI responders and non-responders. SSRI responders and never-depressed participants were similar in their left hemispheric lateralization for evaluating emotional words. In contrast, SSRI non-responders showed a relative shift towards RH processing of negative words, and a strong bias toward negative evaluation of words pre- sented to the RH. The results are discussed within the context of a biological–cognitive model of vulner- ability to depression. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Depression is characterized by a distinct neuropsychological profile, involving hypoactivity in left frontal and right posterior areas, and hyperactivity in right frontal areas. Converging evidence for this pattern of activity comes from several lines of evidence including emotional responses associated with brain lesions (Jorge, Robinson, Starkstein, & Arndt, 1993; Robinson, Bolduc, & Price, 1987) electrophysiological (EEG) measures (Coan & Allen, 2004; Henriques & Davidson, 1991; Thibodeau, Jorgensen, & Kim, 2006), and studies of perceptual asymmetries (Bruder, Stewart, McGrath, Deliyannides, & Quitkin, 2004; Bruder, Wexler, Stewart, Price, & Quitkin, 1999; Bruder et al., 2002; Heller, Etienne, & Miller, 1995; Pine et al., 2000). The frontal asymmetry is thought to reflect asym- metries in motivational control, with left frontal activity associated with behavioral approach and right frontal activity associated with behavioral withdrawal (Davidson, 1993; Harmon-Jones, 2003). De- creased activity in right hemisphere (RH) temporo-parietal areas is thought to reflect the hypoarousal that is characteristic of depres- sion (Heller, 1993; Heller & Nitschke, 1998). According to Davidson’s (1998) diathesis-stress hypothesis, this pattern of frontal asymmetry reflects a cognitive and biological pre- disposition to a negative affective style, which increases emotional reactivity to stressful life events and can lead to depression. Although a large body of research has confirmed relations between patterns of neurophysiological activity and personality (Coan & Allen, 2004; Sutton & Davidson, 1997) or affective variables (David- son, Ekman, Saron, Senulis, & Friesen, 1990; Jackson et al., 2003; Tomarken, Davidson, & Henriques, 1990; Tomarken, Davidson, Wheeler, & Doss, 1992), much less is known about the cognitive mechanisms that might mediate the relationship between neuro- physiological function and vulnerability to depression (Caccioppo, 2004; Davidson, 2004). The present study examined hemispheric differences in the evaluation of emotional words in never-depressed and previously-depressed individuals, in order to test the hypothe- sis that vulnerability to depression is associated with a negative pro- cessing bias in language that is specifically linked to the RH. The pattern of asymmetry that is typically observed in depres- sion may reflect vulnerability and not depression per se, as it is also observed in individuals at risk of depression, including previously- depressed individuals (Gotlib, Ranganath, & Rosenfeld, 1998; Henriques & Davidson, 1990), adolescents (Tomarken, Dichter, Garber, & Simien, 2004) and infants of depressed mothers (Field & Diego, 2008), as well as individuals with a family history of depression (Bruder et al., 2004, 2005; Bruder, Tenke, Warner, & Weissman, 2007), and children at risk for depression (Hayden et al., 2008; Shankman et al., 2005). Prospective studies show that rightward frontal asymmetry predicts the onset of depression in adolescents (Pössel, Lo, Fritz, & Seemann, 2008), and that rightward frontal asymmetry in infancy predicts stable behavioral inhibition in childhood (Fox, Henderson, Rubin, Calkins, & Schmidt, 2001). Thus, this atypical pattern of hemispheric asymmetry appears to be a stable trait which is present in both those at risk for and in remission from depression. 0278-2626/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.bandc.2010.09.003 ⇑ Corresponding author. Address: School of Psychology, Victoria University of Wellington, PO Box 600, Wellington 6012, New Zealand. E-mail address: gina.grimshaw@vuw.ac.nz (G.M. Grimshaw). Brain and Cognition 74 (2010) 332–340 Contents lists available at ScienceDirect Brain and Cognition journal homepage: www.elsevier.com/locate/b&c