A circuit perspective on olfaction – how learning and context shape the propagation of information between brain areas

Introduction

Sensory information is initially processed in specialized brain areas, but only integration with previously acquired knowledge provides meaningful information for flexible action selection. This requires the propagation of information from sensory to association areas, where sensory information is put into context and memories are acquired.

Importance of the Entorhinal-Hippocampal Network

The entorhinal-hippocampal network is of particular importance for information integration and memory formation. Recent findings about learning-induced changes in sensory areas raise the question of whether they occur independently or reflect altered top-down influence of the abundant feedback projections from associative areas.

Knowledge Gaps

While learning- and context-related changes of activity have been described for individual brain areas, it is largely unknown how learning affects the propagation of information between areas.

Project Aim

The proposed project aims to dissect the mechanisms by which learning and context shape the propagation of sensory information from the olfactory system to the entorhinal-hippocampal network in mice. Olfaction provides unique features to address this aim:

1. A short pathway from sensory to association areas.
2. A discrete time frame for information sampling by respiration.
3. The capability of mice to quickly learn odor-guided tasks.

Main Hypothesis

The main hypothesis of this project is that timing and synchrony of neuronal activity are key parameters in determining the propagation of information between brain areas and that they are affected by learning and context through feedback projections from association areas.

Methodology

This hypothesis will be tested by:

• Simultaneous electrophysiological recordings in the olfactory bulb, piriform cortex, lateral entorhinal cortex, and hippocampus during the learning of odor-reward associations.
• Combined with optogenetic manipulations and anatomical assessment of connectivity between these areas.

Expected Outcomes

This project will reveal the mechanisms by which learning and context change the propagation of information between brain areas.