The hippocampus encodes delay and value information during delay-discounting decision making
- Doshisha University, Japan
- RIKEN Center for Brain Science, Japan
- University of Tsukuba, Japan
Abstract
The hippocampus, a region critical for memory and spatial navigation, has been implicated in delay discounting, the decline in subjective reward value when a delay is imposed. However, how delay information is encoded in the hippocampus is poorly understood. Here we recorded from CA1 of mice performing a delay-discounting decision-making task, where delay lengths, delay positions, and reward amounts were changed across sessions, and identified subpopulations of CA1 neurons which increased or decreased their firing rate during long delays. The activity of both delay-active and -suppressive cells reflected delay length, delay position, and reward amount; however manipulating reward amount differentially impacted the two populations, suggesting distinct roles in the valuation process. Further, genetic deletion of NMDA receptor in hippocampal pyramidal cells impaired delay-discount behavior and diminished delay-dependent activity in CA1. Our results suggest that distinct subclasses of hippocampal neurons concertedly support delay-discounting decisions in a manner dependent on NMDA receptor function.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files.
Article and author information
Author details
Funding
Japan Society for the Promotion of Science (16K15196)
- Akira Masuda
Japan Agency for Medical Research and Development (Brain/MINDS)
- Shigeyoshi Fujisawa
Uehara Memorial Foundation
- Akira Masuda
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institute of Health. The study was approved by the Institutional Animal Care and Use Committee of the RIKEN Institute in Wako (approval number H27-2-239(6)), in conformity with Article 24 of the RIKEN regulations for animal experiments. All surgery was performed under isoflurane anesthesia, and every effort was made to minimize suffering.
Copyright
© 2020, Masuda et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The hippocampus encodes delay and value information during delay-discounting decision making
eLife 9:e52466.
https://doi.org/10.7554/eLife.52466
Further reading
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When holding visual information temporarily in working memory (WM), the neural representation of the memorandum is distributed across various cortical regions, including visual and frontal cortices. However, the role of stimulus representation in visual and frontal cortices during WM has been controversial. Here, we tested the hypothesis that stimulus representation persists in the frontal cortex to facilitate flexible control demands in WM. During functional MRI, participants flexibly switched between simple WM maintenance of visual stimulus or more complex rule-based categorization of maintained stimulus on a trial-by-trial basis. Our results demonstrated enhanced stimulus representation in the frontal cortex that tracked demands for active WM control and enhanced stimulus representation in the visual cortex that tracked demands for precise WM maintenance. This differential frontal stimulus representation traded off with the newly-generated category representation with varying control demands. Simulation using multi-module recurrent neural networks replicated human neural patterns when stimulus information was preserved for network readout. Altogether, these findings help reconcile the long-standing debate in WM research, and provide empirical and computational evidence that flexible stimulus representation in the frontal cortex during WM serves as a potential neural coding scheme to accommodate the ever-changing environment.
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When navigating environments with changing rules, human brain circuits flexibly adapt how and where we retain information to help us achieve our immediate goals.
