Temporal dynamics of affective scene processing in the healthy adult human brain

Abstract

Understanding how the brain distinguishes emotional from neutral scenes is crucial for advancing brain-computer interfaces, enabling real-time emotion detection for faster, more effective responses, and improving treatments for emotional disorders like depression and anxiety. However, inconsistent research findings have arisen from differences in study settings, such as variations in the time windows, brain regions, and emotion categories examined across studies. This review sought to compile the existing literature on the timing at which the adult brain differentiates basic affective from neutral scenes in less than one second, as previous studies have consistently shown that the brain can begin recognizing emotions within just a few milliseconds. The review includes studies that used electroencephalography (EEG) or magnetoencephalography (MEG) in healthy adults to examine brain responses to emotional versus neutral images within one second. Articles of interest were limited to the English language but not to any publication year. Excluded studies involved only patients (of any diagnosis), participants under age 18 (since emotional processing can differ between adults and younger individuals), non-passive tasks, low temporal resolution techniques, time intervals over one second, and animals. Of the 3045 screened articles, 19 met these criteria. Despite the variations between studies, the earliest onset for heightened brain responses to basic affective scenes compared to neutral ones was most commonly observed within the 250-300 ms time window. To the best of our knowledge, this review is the first to synthesize data on the timing of brain differentiation between emotional and neutral scenes in healthy adults.

Keywords: Affective pictures; EEG; Emotion differentiation/discrimination/classification; MEG; Pleasant; Temporal dynamics; Unpleasant.

Fig. 1.

PRISMA diagram summarizing the literature search, screening, selection, and inclusion of studies.

Fig. 2.

Summary of Study Results (sorted by time windows). A summary of the study findings highlighting the brain responses of healthy adults viewing pleasant (positive) and unpleasant (negative) images compared to neutral ones during a 0-1 second (1000 ms) time window. The blue and red lines represent the time windows reported by each study for pleasant versus neutral and unpleasant versus neutral conditions, respectively. The plot includes detailed information for each study, including the author and year, the brain frequency associated with the relevant time window, the duration of the time window in milliseconds, and the specific brain regions or channels/sensors involved. For studies reporting multiple results across different frequency bands, the results are separated and denoted with asterisks (e.g., ** or *** indicate results from one study).