Summary: When it’s more helpful to think ahead, people rely on the memories of previous experiences to help make choices.
Replaying prior experiences when learning something new can improve the brain’s ability to make future plans and preserve memories of the past, finds new research by UCL neuroscientists.
The study, published in PNAS, used brain imaging techniques to detect activity in the brains of 24 participants, while taking part in a maze task.
As part of the experiment, participants were asked to make a series of choices between shapes in order to reach rewards.
Each shape would lead down a different path made up of a sequence of pictures, followed by reward points at the end. The participants’ goal was to keep track of the best path, because the reward points at the end changed over time.
The results showed that when it was most helpful to think ahead, participants replayed memories of previous experiences before making a choice.
Researchers also examined the brain activity of participants during a brief pause after receiving feedback. Here they found that participants increasingly thought about the less frequently visited paths in the maze – indicating that a memory was being preserved.
Interestingly, replay events were very fast – completing a path in a fraction of a second.
The results demonstrate how replaying experiences at different times can relate to two separate cognitive functions. However, both effects were related to increased activity in regions of the brain, including the hippocampus, which is crucial for memory.
Lead author, Dr Elliott Wimmer (UCL Queen Square Institute of Neurology and The Max Planck UCL Centre for Computational Psychiatry and Ageing Research), said: “Our research found that replay may aid both key mental abilities, decision-making and memory, but at different times.
“When it’s time to make a decision, replay focused on the task at hand, supporting a role for memory in planning. But during more idle periods, replay was stronger for previous memories, which may help sustain old experiences.”
The team now hope that the findings will help future research into conditions such as mood disorders and dementia.
Dr Wimmer said: “The brain may prioritise one function over the other based on the situation. By finding two distinct functions of replay, these results may guide future research on decision-making and memory problems in psychiatric and memory disorders.”
Funding: The research was funded by Wellcome and the Max Planck Society.
About this decision-making and memory research news
Author: Poppy Danby
Contact: Poppy Danby – UCL
Image: The image is in the public domain
Original Research: Open access.
“Distinct replay signatures for prospective decision-making and memory preservation” by Elliott Wimmer et al. PNAS
Distinct replay signatures for prospective decision-making and memory preservation
Theories of neural replay propose that it supports a range of functions, most prominently planning and memory consolidation.
Here, we test the hypothesis that distinct signatures of replay in the same task are related to model-based decision-making (“planning”) and memory preservation.
We designed a reward learning task wherein participants utilized structure knowledge for model-based evaluation, while at the same time had to maintain knowledge of two independent and randomly alternating task environments.
Using magnetoencephalography and multivariate analysis, we first identified temporally compressed sequential reactivation, or replay, both prior to choice and following reward feedback. Before choice, prospective replay strength was enhanced for the current task-relevant environment when a model-based planning strategy was beneficial.
Following reward receipt, and consistent with a memory preservation role, replay for the alternative distal task environment was enhanced as a function of decreasing recency of experience with that environment. Critically, these planning and memory preservation relationships were selective to pre-choice and post-feedback periods, respectively.
Our results provide support for key theoretical proposals regarding the functional role of replay and demonstrate that the relative strength of planning and memory-related signals are modulated by ongoing computational and task demands.