Prior Reward Conditioning Dampens Hippocampal and Striatal Responses during an Associative Memory Task.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Decision Science

Background:

• Reward-based learning typically enhances memory encoding.
• The persistence of reward-driven memory benefits in different contexts is not well understood.
• Understanding this is crucial for applications in education and rehabilitation.

Purpose of the Study:

• To investigate if reward at encoding confers a generalized memory advantage across different learning episodes.
• To determine if reward-induced memory benefits persist in a non-rewarded context.
• To explore the neural mechanisms underlying the transfer (or lack thereof) of reward effects on memory.

Main Methods:

• Participants underwent a picture-encoding task with monetary rewards, followed by a picture-location association memory task without reward.
• fMRI (functional Magnetic Resonance Imaging) was used to measure brain activity during encoding and memory tasks.
• Functional connectivity analysis was performed during delayed recall to assess interactions between brain regions.

Main Results:

• Monetary reward at encoding increased ventral striatum activity and pleasantness ratings but did not improve subsequent memory performance in a new task.
• A trend towards impaired memory accuracy was observed for initially high-rewarded items compared to low-rewarded items.
• fMRI revealed reduced activity in reward (ventral striatum) and memory (hippocampus) circuits for previously high-rewarded items, and decreased hippocampal-striatal connectivity during delayed recall.

Conclusions:

• Acquired reward value can lead to a downward adjustment signal in the brain's reward circuit when encountered in a non-rewarded context.
• This process may disengage memory-reward networks, potentially hindering new associative learning.
• While reward aids initial learning, it can subsequently impede memory formation and neural responses in key memory and reward circuits.