An updated emotional mnemonic discrimination task with matched alternate forms for longitudinal and intervention studies

Mnemonic discrimination tasks (MDTs) provide sensitive measures of episodic memory and hippocampal function and have been widely used to examine memory in a wide array of health and disease conditions across the lifespan. Emotional MDTs (eMDTs) extend this approach by incorporating negative, neutral, and positive stimuli, enabling the investigation of interactions between emotion and memory. Despite its growing use, a major limitation of the eMDT is the absence of alternate forms for repeated testing, restricting its application in longitudinal and intervention studies. This study aimed to develop and optimize two matched alternate forms of the eMDT while expanding and modernizing the original stimulus repository. We curated a larger set of naturalistic scene images, increased demographic representation of the images, and generated two non-overlapping stimulus sets. Images were matched on emotional valence, arousal, lure similarity, and behavioral performance through a series of iterative optimization procedures. To ensure consistency with prior work, performance characteristics of the revised stimulus sets were benchmarked against the original eMDT. Results demonstrated that matching on image characteristics utilized in the original stimulus set was insufficient to achieve behavioral equivalence across alternate forms. Incorporating item-level memory performance substantially improved matching between sets. The finalized sets were matched on stimulus characteristics and produced comparable behavioral performance estimates while preserving the emotional memory effects observed in the original eMDT. Together, these findings provide the first matched alternate forms of the eMDT and an expanded stimulus repository for repeated assessment of emotional memory. These resources will facilitate intervention and clinical studies investigating emotional memory and hippocampal function.