Protocols to Study Declarative Memory Formation in Mice and Humans:Optogenetics and Translational Behavioral Approaches

Azza Sellami; Alice Shaam Al Abed; Laurent Brayda-Bruno; Nicole Etchamendy; Stéphane Valério; Marie Oulé; Laura Pantaléon; Valérie Lamothe; Mylène Potier; Katy Bernard; Maritza Jabourian; Cyril Herry; Nicole Mons; Aline Marighetto

doi:10.21769/BioProtoc.2888

Protocols to Study Declarative Memory Formation in Mice and Humans:Optogenetics and Translational Behavioral Approaches

Bio Protoc. 2018 Jun 20;8(12):e2888. doi: 10.21769/BioProtoc.2888.

Authors

Azza Sellami^{1

2}, Alice Shaam Al Abed^{1

2}, Laurent Brayda-Bruno^{1

2}, Nicole Etchamendy^{1

2}, Stéphane Valério^{1

2}, Marie Oulé^{1

2}, Laura Pantaléon^{1

2}, Valérie Lamothe^{1

2}, Mylène Potier^{1

2}, Katy Bernard³, Maritza Jabourian³, Cyril Herry^{1

2}, Nicole Mons^{2

4}, Aline Marighetto^{1

2}

Affiliations

¹ Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U1215, INSERM, Bordeaux, France.
² Université de Bordeaux, Bordeaux, France.
³ Institut de Recherche Internationale Servier, Suresnes, France.
⁴ Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, UMR 5287, CNRS, Pessac, France.

Abstract

Declarative memory formation depends on the hippocampus and declines in aging. Two functions of the hippocampus, temporal binding and relational organization (Rawlins and Tsaltas, 1983; Eichenbaum et al., 1992 ; Cohen et al., 1997 ), are known to decline in aging (Leal and Yassa, 2015). However, in the literature distinct procedures have been used to study these two functions. Here, we describe the experimental procedures used to investigate how these two processes are related in the formation of declarative memory and how they are compromised in aging ( Sellami et al., 2017 ). First, we studied temporal binding using a one-trial learning procedure: trace fear conditioning. It is classical Pavlovian conditioning requiring temporal binding since a brief temporal gap separates the conditioned stimulus (CS) and unconditioned stimulus (US) presentations. We combined the trace fear condition procedure with an optogenetic approach, and we showed that the temporal binding relies on dorsal (d)CA1 activity over temporal gaps. Then, we studied the interaction between temporal binding and relational organization in declarative memory formation using a two-phase radial-maze task in mice and its virtual analog in humans. The behavioral procedure comprises an initial learning phase where subjects learned the constant rewarding /no rewarding valence of each arm, followed by a test phase where the reward contingencies among the arms remained unchanged but where the arms were recombined to assess flexibility, a cardinal property of declarative memory. We demonstrated that dCA1-dependent temporal binding is necessary for the development of a relational organization of memories that allows flexible declarative memory expression. Furthermore, in aging, the degradation of declarative memory is due to a reduction of temporal binding capacity that prevents relation organization.

Keywords: Archeorhodopsin; Channelrhodopsin; Optogenetics; Radial maze; Trace fear conditioning; Virtual radial maze.