Naturalistic Stimuli in Affective Neuroimaging: A Review

Abstract

Naturalistic stimuli such as movies, music, and spoken and written stories elicit strong emotions and allow brain imaging of emotions in close-to-real-life conditions. Emotions are multi-component phenomena: relevant stimuli lead to automatic changes in multiple functional components including perception, physiology, behavior, and conscious experiences. Brain activity during naturalistic stimuli reflects all these changes, suggesting that parsing emotion-related processing during such complex stimulation is not a straightforward task. Here, I review affective neuroimaging studies that have employed naturalistic stimuli to study emotional processing, focusing especially on experienced emotions. I argue that to investigate emotions with naturalistic stimuli, we need to define and extract emotion features from both the stimulus and the observer.

Keywords: affective neuroscience; brain imaging; emotion; fMRI; movies; naturalistic stimuli; stories.

FIGURE 1

A framework for extracting emotion features in naturalistic paradigms. (A) Defining emotion features with a consensual component model of emotional processing (see, e.g., Mauss and Robinson, 2009; Anderson and Adolphs, 2014; Sander et al., 2018). First, the observer evaluates the stimulus’s relevance during an emotion elicitation step. Second, the elicited emotion leads to automatic changes in several functional components. (B) Extracting emotion features and example feature time series. With naturalistic paradigms, emotion features can be extracted both from the stimulus and the observer. Stimulus features are related to perceived emotions (here, depicted for a movie stimulus), observer features model experienced emotions. The figure shows examples of potential emotion features and their time series. In the next methodological step, the stimulus and observer feature time series are used to model the neural time series.

FIGURE 2

Summary of brain regions correlating with emotion features. Dots denote an observed association between the brain region (rows) and the emotion feature (columns). Color panels denote feature categories (from left to right): low-level auditory features (red), object-level features (blue), portrayed emotions (green), emotion elicitation (violet), interoception (orange), behavior (yellow), affective dimensions (brown), emotion categories (pink), and emotional alignment (gray). Directionality of association and more detailed anatomical locations are listed in Supplementary Table 1.

FIGURE 3

Summary of functional networks correlating with emotion features. Dots denote an observed association between the network (rows) and the emotion feature (columns). Color panels denote feature categories (from left to right): low-level auditory and visual features (red), object-level features (blue), emotion elicitation (violet), interoception (orange), affective dimensions (brown), and emotion categories (pink). Directionality of association and more detailed anatomical locations are listed in Supplementary Table 2.