Time-Delay Effect on Prospective Memory and Neural Mechanisms: An fNIRS Study in Young Adults
Poster No:
767
Submission Type:
Late-Breaking Abstract Submission
Authors:
Kristal Y. T. Chan1, Victoria W. T. Chan1, Tinky O. T. Ho1, Mandy H. M. Yu1, Hui Zhang1, David H.K. Shum1
Institutions:
1The Hong Kong Polytechnic University, Hong Kong, Hong Kong
First Author:
Co-Author(s):
Introduction:
Prospective memory (PM) is the ability to remember and execute intended actions at a future time (Brandimonte et al., 2014). Despite its importance, the influence of time delay between encoding and retrieval on PM performance remains unclear, with previous studies yielding mixed results and often lacking ecological validity. Furthermore, the neural mechanisms underlying PM are not well understood. This study aimed to address these gaps by examining the impact of time delay on PM performance and its neural mechanisms in young adults, utilizing functional near-infrared spectroscopy (fNIRS) techniques. Building on the work of Leung et al. (2025) and Koo et al. (2022), we compare PM performance under immediate conditions and after a 1-week delay. To enhance ecological validity and overcome limitations of prior research, we employ a dual-task paradigm incorporating a visual perceptual (VP) task. Additionally, we explore the brain regions activated during PM tasks and assess how time delay influences neural activity, providing new insights into the neurobiological basis of PM.
Methods:
Seventy young adults were randomly assigned to either an immediate or a 1-week delay condition. In session one, participants completed a VP task. In session two, they performed a dual-task paradigm with an embedded PM task, while neural activity was recorded using fNIRS (see Figure 1). The tasks were based on the dual-task paradigm by Einstein and McDaniel (1990; see Figure 2) and adapted from Flowers et al. (2004). Participants viewed stimuli on a screen, consisting of English alphabets or symbols, and pressed a key when a green border (PM cue) appeared. Neural activity was measured with a continuous wave fNIRS instrument (NIRSport2), tracking oxyhemoglobin changes. Cortical activation was analyzed using the General Linear Model implemented in the NIRS-SPM package within MATLAB. A region of interest (ROI) approach was used to localize NIRS channels on a standardized template, identifying five ROIs: left and right dorsolateral prefrontal cortex, frontopolar prefrontal cortex, and left and right lateral prefrontal cortex (BA10).
Results:
In the immediate condition, 24 participants successfully remembered the PM tasks, compared to 19 participants in the 1-week delay condition. However, the chi-square test results indicated no significant association between remembering the PM task and the duration of the delay. Behavioral analysis revealed a significant main effect of time delay on PM performance, with PM accuracy significantly reduced in the 1-week delay condition (0.44) compared to the immediate condition (0.67). For the ongoing VP task, accuracy decreased significantly in session 2 (from 0.94 to 0.88) when the PM task was embedded in the immediate condition, although reaction times did not differ between the two sessions in either condition. The fNIRS results analysis indicated no significant differences in brain activation across the five regions of ROIs between the two sessions in the immediate condition. However, in the 1-week delay condition, participants who remembered the PM task exhibited significantly higher activation in the right BA10.
Conclusions:
This study enhances our understanding of the effect of time delay on event-based PM and its neural basis. The reduction in PM accuracy after a 1-week delay underscores the importance of timing in PM processes. Increased activation in the right BA10 suggests this region's role in supporting delayed PM retrieval. While these findings advance PM theories, they should be cautiously interpreted due to the small sample size. Further research with larger samples is needed to confirm these results and explore the neural mechanisms of PM.
Higher Cognitive Functions:
Higher Cognitive Functions Other 1
Learning and Memory:
Learning and Memory Other
Novel Imaging Acquisition Methods:
NIRS 2
Keywords:
ADULTS
Cognition
Memory
Near Infra-Red Spectroscopy (NIRS)
Other - Prospective Memory
1|2Indicates the priority used for review
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Einstein, G. O., & McDaniel, M. A. (1990). Normal aging and prospective memory. Journal of Experimental Psychology: Learning, memory, and cognition, 16(4), 717.
Flowers, D. L., Jones, K., Noble, K., VanMeter, J., Zeffiro, T. A., Wood, F. B., & Eden, G. F. (2004). Attention to single letters activates left extrastriate cortex. NeuroImage (Orlando, Fla.), 21(3), 829–839. https://doi.org/10.1016/j.neuroimage.2003.10.002
Koo, Y. W., Neumann, D. L., Ownsworth, T., Yeung, M. K., & Shum, D. H. K. (2022). Understanding the Neural Basis of Prospective Memory Using Functional Near-Infrared Spectroscopy. Frontiers in Human Neuroscience., 16. https://doi.org/10.3389/fnhum.2022.905491
Leung, A. H. T., Chan, C. C. S., Kwong, C. M. Y., Leung, C. H. Y., Cao, Y., Yu, M. H. M., Chan, R. C. K., & Shum, D. H. K. (2025). The effect of time delay on young adults’ prospective memory. Manuscript submitted for publication.