Aller au contenuAller au menuAller à la recherche

Séminaire - Jozsef Csicsvari Mnemonic Coding and Reactivation in the Medial Entorhinal Cortex

Abstract :

Austrian Institute of Science and Technology, Vienna.

The superficial layers of the Medial Entorhinal Cortex (MEC) contain spatially-selective units, a subset of which form a characteristic hexagonal pattern of firing fields, known as grid cells.  This arrangement of firing fields is in part maintained between different environments, leading to the hypothesis that such cells play a principle role in path integration. Although, data gathered from lesion and transgenic experiments implicate the MEC in mnemonic processes, little is known how grid cells may participate in encoding of spatial memory.  We simultaneousness recorded from the superficial layers of the MEC and the hippocampus while the animal first explored an open field and subsequently performed a delay-match-to-sample task on a modified T-maze. 

Grid cells maintained their joint firing patterns between the open field and T-maze but showed a reduction in grid field spacing on the T-maze, indicating a denser coding of space during the task. Grid cells also showed rate remapping between different phases of the task, suggesting that such cells encode for task-related features such as trial-type or the future choice of the animal. During delay periods, or at the choice point at the T-maze, grid cells often decoupled their activity from the current location of the animal and participated in compressed temporal sequences that reflected consecutive places on the T-maze. These place sequences often reached one of the side arms of the maze and predicted the future arm choice of the animal or represented the previous visit. However these MEC trajectory sequences occurred independently from the activation of hippocampal place-related assemblies.  

This work demonstrated that, similar to the hippocampus, MEC region and particularly grid cells are involved in mnemonic processing, and, in certain conditions, they acted independently from the hippocampus. 

Selected publications

Schoenenberger P, O’Neill J, Csicsvari J (2016) Activity-dependent plasticity of hippocampal place maps, Nature Communications, in press

Csicsvari J, Dupret D. (2014) Sharp wave/ripple network oscillations and learning-associated hippocampal maps. Phil Trans R Soc B 369:20120528.

Dupret D, O'Neill J, Csicsvari J (2013) Dynamic reconfiguration of hippocampal interneuron circuits during spatial learning. Neuron, 78:166-80.

Allen K, Rawlins J, Bannerman D, Csicsvari J (2012) Hippocampal place cells can encode multiple trial-dependent features through rate remapping. J Neurosci, 32:14752-66.

About IST Austria

The Institute of Science and Technology Austria (IST Austria) is a young international institute dedicated to basic research and graduate education in the natural and mathematical sciences, located in Klosterneuburg on the outskirts of Vienna. Established jointly by the federal government of Austria and the provincial government of Lower Austria, the Institute was inaugurated in 2009 and will grow to about 90 research groups by 2026.