High-Throughput Task to Study Memory Recall During Spatial Navigation in Rodents.

Lucia Morales,David P Tomàs,Josep Dalmau,Jaime De La Rocha,Pablo E Jercog

doi:10.3389/fnbeh.2020.00064

Abstract

Spatial navigation is one of the most frequently used behavioral paradigms to study memory formation in rodents. Commonly used tasks to study memory are labor-intensive, preventing the simultaneous testing of multiple animals with the tendency to yield a low number of trials, curtailing the statistical power. Moreover, they are not tailored to be combined with neurophysiology recordings because they are not based on overt stereotyped behavioral responses that can be precisely timed. Here we present a novel task to study long-term memory formation and recall during spatial navigation. The task consists of learning sessions during which mice need to find the rewarding port that changes from day to day. Hours after learning, there is a recall session during which mice search for the location of the memorized rewarding port. During the recall sessions, the animals repeatedly poke the remembered port over many trials (up to ∼20) without receiving a reward (i.e., no positive feedback) as a readout of memory. In this task, mice show memory of port locations learned on up to three previous days. This eight-port maze task requires minimal human intervention, allowing for simultaneous and unsupervised testing of several mice in parallel, yielding a high number of recall trials per session over many days, and compatible with recordings of neural activity.

Highlights

Relevance in the Study of Spatial NavigationSuccessful navigation is crucial for survival and requires the memorization of locations and paths
The main goal for the design of the memory task presented here was to obtain a large number of trials during a spatial memory recall session with minimal human intervention
When the animal walked into the trigger zone, the reward window started, lasting up to 6 s while a sound cued the animal about the availability of water at the rewarding port

Summary

Introduction

Relevance in the Study of Spatial NavigationSuccessful navigation is crucial for survival and requires the memorization of locations and paths. It is believed that the hippocampus registers relevant events creating episodic memories that are stored in a mental structure called a “cognitive map” (Tolman, 1948). The discovery by O’Keefe and Dostrovsky (1971) of spatially tuned cells in the hippocampus (i.e., place-cells), gave support to the idea that the cognitive map internally represents in space (mostly) and time, events remembered during navigation (O’Keefe and Nadel, 1978). Based on this interpretation, the hippocampal spatially informative neuronal representation became the major focus of most investigations, leaving unattended the study of the hippocampal role in other types of memories. Our task intends to investigate different components of mnemonic objects.

Methods

Results

Conclusion