Human Amygdala Represents the Complete Spectrum of Subjective Valence

Abstract

Although the amygdala is a major locus for hedonic processing, how it encodes valence information is poorly understood. Given the hedonic potency of odor stimuli and the amygdala's anatomical proximity to the peripheral olfactory system, we combined highresolution fMRI with pattern-based multivariate techniques to examine how valence information is encoded in the amygdala. Ten human subjects underwent fMRI scanning while smelling 9 odorants that systematically varied in perceived valence. Representational similarity analyses showed that amygdala codes the entire dimension of valence, ranging from pleasantness to unpleasantness. This unidimensional representation significantly correlated with self-reported valence ratings but not with intensity ratings. Furthermore, within-trial valence representations evolved over time, prioritizing earlier differentiation of unpleasant stimuli. Together, these findings underscore the idea that both spatial and temporal features uniquely encode pleasant and unpleasant odor valence in the amygdala. The availability of a unidimensional valence code in the amygdala, distributed in both space and time, would create greater flexibility in determining the pleasantness or unpleasantness of stimuli, providing a mechanism by which expectation, context, attention, and learning could influence affective boundaries for guiding behavior.

Subcortical Facilitation of Behavioral Responses to Threat

“…This result is in line with evidence that both pulvinar and amygdala respond selectively to ancestral threats 19,31 , and provides support for recent theoretical proposals that the superior colliculus-pulvinar pathway may be critical not only for detection of visual threat, but also for coordinating behavioral responses to threat 15 . Note, however, that the current results seem unlikely to reflect activity in amygdala alone, as the human amygdala appears to encode information about both positive and negative valence 55 , and we did not observe a monocular advantage for images with positive valence (the pleasant nature scenes presented in Experiment 2).…”

Orbitofrontal Cortex Activity and Connectivity Predict Future Depression Symptoms in Adolescence

“…The present study provides the first evidence that alterations in OFC activity predict future depression symptoms in never-depressed adolescent females who are at high familial risk for developing depression, indicating that aberrant OFC activity and connectivity may represent a vulnerability factor for depression. Due to OFC’s role in the representation and integration of motivationally salient information (22, 23), flexible value-based computation (54–59) and adaptive decision-making (60–62), the present findings have the potential to clarify how complex representations of loss and reward, as well as their integration, contribute to the development of future depression.…”

“…OFC represents the complete dimension of subjective valence ranging from unpleasant to pleasant (22, 23). Due to strong anatomical connectivity with sensory, striatal, limbic and insular regions, OFC plays a critical role in integrating loss- and reward-related information (19, 24).…”

Amygdala and nucleus accumbens involvement in appetitive extinction

“…This unexpected finding suggests that the amygdala plays a specific role in both early and late extinction which needs to be studied in more detail. These exploratory, descriptive results suggest that future studies should try to focus on activation patterns within these regions using pattern analyses like representational similarity analysis (RSA; Jin, Zelano, Gottfried, & Mohanty, 2015), which the present design did not permit because the employed ITI was too short (Visser et al, 2016). This might allow to capture how subnuclei within amygdala and NAcc work in parallel during acquisition but show discernible patterns during extinction.…”