Acetylcholine-modulated plasticity in reward-driven navigation: a computational study

Sara Zannone,Ole Paulsen,Zuzanna Brzosko,Claudia Clopath

doi:10.1038/s41598-018-27393-2

Sara Zannone, Ole Paulsen + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-27393-2

Copy DOI

Abstract

Neuromodulation plays a fundamental role in the acquisition of new behaviours. In previous experimental work, we showed that acetylcholine biases hippocampal synaptic plasticity towards depression, and the subsequent application of dopamine can retroactively convert depression into potentiation. We also demonstrated that incorporating this sequentially neuromodulated Spike-Timing-Dependent Plasticity (STDP) rule in a network model of navigation yields effective learning of changing reward locations. Here, we employ computational modelling to further characterize the effects of cholinergic depression on behaviour. We find that acetylcholine, by allowing learning from negative outcomes, enhances exploration over the action space. We show that this results in a variety of effects, depending on the structure of the model, the environment and the task. Interestingly, sequentially neuromodulated STDP also yields flexible learning, surpassing the performance of other reward-modulated plasticity rules.

Highlights

In order to survive, animals have to learn to interact with their environment in an effective way
Research is increasingly focusing on elucidating the effects of neuromodulation on Spike-Timing-Dependent Plasticity (STDP), a form of plasticity that depends on exact spike timings
Acetylcholine has been shown to modulate synaptic plasticity in both directions[28], we found that acetylcholine biased hippocampal STDP towards depression

Summary

Introduction

Animals have to learn to interact with their environment in an effective way. We found that dopamine can potentiate hippocampal synapses that were previously active, even when applied after a delay[21,22], bridging the gap between synaptic and behavioural timescales. This supports the concept of an eligibility trace, which has been theorized and employed in computational modelling. Acetylcholine has been shown to modulate synaptic plasticity in both directions[28], we found that acetylcholine biased hippocampal STDP towards depression This effect could be retroactively converted into potentation by consequent application of dopamine[22]. This allows us to deepen our mechanistic understanding of the model, and gain some insight into the complex relationship between synaptic and behavioural learning

Methods

Results

Discussion

Conclusion