The general thesis examined here is that experienced emotions are founded on the activation of neural circuits that evolved in the mammalian brain to ensure the survival of individuals and their progeny. Primitively, these motive circuits were engaged by external stimuli that are appetitive and potentially life sustaining, or alternatively, represent threats to the organism's survival. The psychobiological consequences of this neural firing are potentially twofold: On the one hand, they engage sensory systems that increase attention and facilitate perceptual processing, and on the other, they initiate reflex responses that mobilize the organism and prompt motor action. Research with animals (e.g., Davis, 2000; Fanselow and Poulos, 2005; Kapp et al., 1994; LeDoux, 2003) has defined the key neural structures in this survival network (see Fig. 1: Lang and Davis, 2006; see also, Davis and Lang, 2003): The bilateralamygdalae – two small, almond shaped bundles of nuclei in the temporal lobe – plays a central role. Each amygdala receives input from cortex and thalamus (sensory) and hippocampus (memory), subsequently engaging through the central nucleus and extended amygdala (basal nucleus of the stria terminalis) a range of other brain centers that modulate sensory processing (vigilance), increase related information proces-sing, and activate autonomic and somatic structures that mediate defensive or appetitive actions. It is convenient to consider this survival circuit as organized into two motivational systems, one defensive and associated with reports of unpleasant affect and the other appetitive, associated with pleasant affect. Konorski (1967) early conceived such a motivational typology, keyed to the survival role of the body's many unconditioned reflexes. Exteroceptive reflexes were either preservative (e.g., ingestion, copulation, nurture of progeny) or protective (e.g., withdrawal from or rejection of noxious agents). He further suggested that affective states were consistent with this preservative/protective grouping: Preservative emotions include such affects as sexual passion, joy, and nurturance; fear and anger are protective affects. Dickinson and Dearing (1979) developed Konorski's distinction, renaming the two motivational systems, aversive and attractive, with each again activated by a different, but equally wide range of unconditioned stimuli, determining perceptual-motor patterns and the course of learning. In this general view, affective valence is determined by the dominant motive system: the appetitive system (preservative/attractive) prompts positive affect; the defense system (protective/aversive) is the source of negative affect. Affective arousal reflects the ''intensity'' of motivational mobilization, determined originally by Biological Psychology xxx (2009) xxx–xxx 1 2 3 4 5 6 7 8 Psychophysiological and neuroscience studies of emotional processing undertaken by investigators at the University of Florida Laboratory of the Center for the Study of Emotion and Attention (CSEA) are reviewed, with a focus on reflex reactions, neural structures and functional circuits that mediate emotional expression. The theoretical view shared among the investigators is that expressed emotions are founded on motivational circuits in the brain that developed early in evolutionary history to ensure the survival of individuals and their progeny. These circuits react to appetitive and aversive environmental and memorial cues, mediating appetitive and defensive reflexes that tune sensory systems and mobilize the organism for action and underly negative and positive affects. The research reviewed here assesses the reflex physiology of emotion, both autonomic and somatic, studying affects evoked in picture perception, memory imagery, and in the context of tangible reward and punishment, and using the electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI), explores the brain's motivational circuits that determine human emotion.