Decoding the neural representation of affective states Laura B. Baucom, Douglas H. Wedell, Jing Wang, David N. Blitzer, Svetlana V. Shinkareva ⁎ University of South Carolina, Columbia, SC, USA abstract article info Article history: Received 30 December 2010 Revised 21 June 2011 Accepted 12 July 2011 Available online 23 July 2011 Keywords: Affective states Valence Arousal Multi-voxel pattern analysis INDSCAL Brain activity was monitored while participants viewed picture sets that reflected high or low levels of arousal and positive, neutral, or negative valence. Pictures within a set were presented rapidly in an incidental viewing task while fMRI data were collected. The primary purpose of the study was to determine if multi-voxel pattern analysis could be used within and between participants to predict valence, arousal and combined affective states elicited by pictures based on distributed patterns of whole brain activity. A secondary purpose was to determine if distributed patterns of whole brain activity can be used to derive a lower dimensional representation of affective states consistent with behavioral data. Results demonstrated above chance prediction of valence, arousal and affective states that was robust across a wide range of number of voxels used in prediction. Additionally, individual differences multidimensional scaling based on fMRI data clearly separated valence and arousal levels and was consistent with a circumplex model of affective states. © 2011 Elsevier Inc. All rights reserved. Introduction The representation and processing of emotional states in the brain has become a fundamental area of study within cognitive neuroscience. Two distinct approaches to understanding affective states have come to the forefront of the study of emotion. The categorical approach builds on the finding of a core set of distinct basic emotions, as demonstrated by studies of the perception of human facial emotional expressions and basic physiological responses of the autonomic nervous system to emotional stimuli (Ekman, 1992a,b). Moreover, these basic emotions, such as anger, fear, disgust, sadness and joy, are thought to be represented by different neural systems (Panksepp, 1992, 1998). An alternative to the categorical approach is to consider the underlying structure of emotions as deriving from two or three basic dimensions of affective processing (Posner et al., 2005; Rolls, 1999; Schlosberg, 1954; Watson and Tellegen, 1985). A widely accepted dimensional model of affect, developed using multidimensional scaling techniques, conceptualizes the affective space as a circle or circumplex with two underlying primary dimensions: valence and arousal (Russell, 1980). Valence reflects the hedonic tone of the emotional state, ranging from positive to negative, while arousal, or activation, reflects the engagement of the organism, ranging from high to low (Roberts and Wedell, 1994). The circumplex model of affect suggests that all emotions or affective states can be distinguished in terms of varying levels of valence and arousal, with two distinct neural systems mediating the representation of affective states (Barrett, 1998). As described above, both the categorical and dimensional approaches to understanding emotional states have support from behavioral and neuroimaging studies. One way to resolve this seeming contradiction is to assume that although emotional states can be described by dimensional variation along valence and arousal, further categorical processing of states may overlay this structure and result in activation of distinct cognitive and neural components. Thus, for example, anger and disgust may both be negative and high arousal states, but their categorical processing leads to different implications, as described in appraisal theory (Lazarus, 1991, 1995). Thus, while the methods we describe in the present study build on the circumplex model of affective states, we believe they may also be applied to categorical approaches. Traditionally, neuroimaging studies have used univariate statistical parametric mapping methods to determine which areas of the brain subserve the processing of emotional stimuli and the generation of emotional states. In a meta-analysis of 162 neuroimaging studies of emotion, Kober et al. (2008) demonstrated that medial frontal areas are co-activated with core limbic structures and that the dorsomedial prefrontal cortex may underlie the generation of emotional states. Consistent with dimensional models of emotion, neuroimaging studies have demonstrated a dissociation of valence and arousal for various stimulus modalities, such as olfactory (Anderson et al., 2003), gustatory (Small et al., 2003), picture (Anders et al., 2004; Grimm et al., 2006; Nielen et al., 2009), word (Kensinger and Corkin, 2004; Lewis et al., 2007; Nielen et al., 2009; Posner et al., 2009), and face (Gerber et al., 2008), as well as emotional experiences induced by the presentation of evocative sentences (Colibazzi et al., 2010). The results of these studies suggest that valence and arousal may be represented in separate neural circuits containing the amygdala, insula, thalamus, dorsal anterior cingulate cortex, and prefrontal regions. These regions are generally consistent with the hypothesis that responses to valence are part of NeuroImage 59 (2012) 718–727 ⁎ Corresponding author at: Department of Psychology, University of South Carolina, Columbia, SC 29208, USA. Fax: +1 803 777 9558. E-mail address: shinkareva@sc.edu (S.V. Shinkareva). 1053-8119/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2011.07.037 Contents lists available at ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg