Shadow-Induced Forgetting in a Game-Based Paradigm on Nonclinical Adults and Its Effects on Consciousness, Emotional Valence, and Temporal Dynamics: Crossover Study

Abstract

Background: Memory suppression transiently disrupts hippocampal activity, leading to suppression-induced forgetting, especially for negative stimuli. However, traditional paradigms such as Think/No-Think rely on explicit control and lack ecological validity. This study introduces a game-based task that implicitly elicits suppression through reversed motor mappings, providing a naturalistic approach to studying memory inhibition. Objective: This study aims to examine how shadow-induced forgetting (ShIF) varies across short-term and long-term intervals (0 hours, 24 hours, and 72 hours), under conscious versus unconscious exposure, and between positive and negative emotional stimuli. Methods: This single-center, within-subjects experimental study involved 56 university students (mean age 23.37, SD 1.84 years) and was conducted between December 1, 2023, and March 1, 2024. Participants learned 36 cue-target image pairs varying in emotional valence (positive and negative). They underwent a game-based paradigm where habitual motor responses were disrupted through reversed key mappings to induce an amnesic shadow. During gameplay, selected cues were presented either consciously or unconsciously, while others served as controls. Memory performance was assessed using Metric for Evaluation of Translation with Explicit Ordering scores (semantic similarity) immediately after intervention (0 hour) and again at 24 hours and 72 hours. Electroencephalography was recorded in a subset of 40 participants to examine neural correlates of memory suppression. Results: ShIF effects were short-term, conscious-dependent, and selective for negative memories. A significant interaction between exposure condition and time (F3.62,199.33=2.7, P=.04, η2p=0.05, 95% CI 0.00-1.00) indicated that the effect varied across time points. Specifically, a significant ShIF effect emerged immediately after the intervention (0 hour) in the conscious condition (t55=−2.86, P=.02, d=0.38) but was absent in the unconscious condition and dissipated by 72 hours. Robust main effects of time (F2,109.99=102.91, P