This chapter reviews behavioral and neuroimaging data illustrating the impact of threat and other emotional signals on attention and perception. It presents both current models and remaining issues concerning the brain mechanisms subserving these effects. A key issue in the framework described here is that perception can be modulated by multiple sources simultaneously, including not only endogenous, exogenous, or object-based attention but also emotional feedback signals from the amygdala, together with other emotion-processing regions. Amygdala responses and its projections to sensory areas can be regulated by signals from distinct brain areas, producing different biasing effects according to the context. The central amygdala has strong outputs to the sympathetic pathways and locus coeruleus in the brainstem. Just as attention can be influenced by feature- or object-based effects, reflecting the readiness of our perceptual systems to preferentially encode certain aspects of sensory, it is also influenced by emotion-based or value-based representations.