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Project

Coordination of neuronal reactivation in the hippocampal-cortical network and the contribution to spatial memory

The hippocampus is a major part of the brain which is associated with spatial navigation, task learning and memory consolidation. However, the hippocampus is not a homogeneous structure and significant molecular, anatomical and functional differences are present along its dorsal-ventral axis. For example, while neurons throughout the hippocampus convey information about the location of an animal, the dorsal and ventral hippocampus differ in the scale at which space is represented.  The dorsal and ventral subregions also receive input from and project to distinct subsets of cortical and subcortical brain regions. The topographical connections with the medial entorhinal cortex (MEC) have been described in detail, and interestingly, the MEC neurons also show different spatial coding properties along the dorsal-ventral axis. 

The goal of my project is to study how neural activity in the dorsal and ventral hippocampal-cortical systems is coordinated and/or acting independently to support navigation and spatial learning, and how this coordination relationship will be changed in different learning phases. A total of six adult C57BL/6J male mice were trained in the maze. There are two different tasks with corresponding mazes used in my project: 1) the continuous alternation spatial task with the figure-8 maze. The animal has to learn to visit different arms alternatively to fetch the reward. The animal in this task requires the hippocampal spatial memory to remember which arm has visited. And 2) freely moving in the open field. The animals were able to freely move in the open field, where the neuron cells in the MEC, for example grid cells and border cells, are involved. All animals were implanted with the 4-shank Neuropixels probe. Three animals for targeting the hippocampus, and the other one for targeting the MEC. I was able to record the neural activities when the animal is performing the behavioral task in the maze.

For this project, I established dual 4-shank Neuropixels probe recordings in unrestrained mice to monitor cellular activity along the dorsal-ventral axis in the hippocampus and the MEC as the mice perform spatial tasks. I have made particular focus on the challenges of identifying the exact location of electrodes in the brain based on histology and electrophysiological signatures, and of managing the trade-off between high-density activity mapping and regional coverage inherent to restrictions on selecting read-out channels on the probes.

 

Date:1 Oct 2019 →  1 Oct 2023
Keywords:memory, hippocampus
Disciplines:Animal experimental psychology
Project type:PhD project