Novelty as a dimension in the affective brain.

Many neuroscience studies have demonstrated that the human amygdala is a central element in the neural workspace that computes affective value. Emerging evidence suggests that novelty is an affective dimension that engages the amygdala independently of other affective properties. This current study is the first in which novelty, valence, and arousal were systematically examined for their relative contributions to amygdala activation during affective processing. Healthy young adults viewed International Affective Picture System (IAPS) images that varied along the dimensions of valence (positive, negative, neutral), arousal (high, mid, low), and novelty (novel, familiar). The results demonstrate that, in comparison to negative (vs. positive) and high (vs. low) arousal stimuli, the amygdala has higher peak responses and a selectively longer time course of activation to novel (vs. familiar) stimuli. In addition, novelty differentially engaged other affective brain areas including those involved in controlling and regulating amygdala responses (e.g., orbitofrontal cortex), as well as those transmitting sensory signals that the amygdala modulates (e.g., occipitotemporal visual cortex). Taken together with other findings, these results support the idea that an essential amygdala function is signaling stimulus importance or salience. The results also suggest that novelty is a critical stimulus dimension for amygdala engagement (in addition to valence and arousal).