Study Motor Skill Learning by Single-pellet Reaching Tasks in Mice

Summary

Persistent practice improves the precision of coordinated movements. Here we introduce a single-pellet reaching task, which is designed to assess the learning and memory of forelimb skill in mice. 

Abstract

Reaching for and retrieving objects require precise and coordinated motor movements in the forelimb. When mice are repeatedly trained to grasp and retrieve food rewards positioned at a specific location, their motor performance (defined as accuracy and speed) improves progressively over time, and plateaus after persistent training. Once such reaching skill is mastered, its further maintenance does not require constant practice. Here we introduce a single-pellet reaching task to study the acquisition and maintenance of skilled forelimb movements in mice. In this video, we first describe the behaviors of mice that are commonly encountered in this learning and memory paradigm, and then discuss how to categorize these behaviors and quantify the observed results. Combined with mouse genetics, this paradigm can be utilized as a behavioral platform to explore the anatomical underpinnings, physiological properties, and molecular mechanisms of learning and memory.

Introduction

Understanding the mechanisms underlying learning and memory is one of the biggest challenges in neuroscience. In the motor system, the acquisition of novel motor skills with practice is often referred as motor learning, whereas the retention of previously learned motor skills is regarded as motor memory¹. Learning a new motor skill is usually reflected in improvement of desired motor performance over time, until a point when the motor skill is either perfected or satisfactorily consistent. For most cases, the acquired motor memory can persist for a long period of time, even in the absence of practice. In humans, neuroimaging studies using positron emission ....

Protocol

Experiments described in this manuscript were performed in accordance with the guidelines and regulations set forth by the University of California, Santa Cruz Institutional Animal Care and Use Committee.

1. Setup (Also See Materials List)

1. Use millet seeds as food pellets.
2. Use a custom-made clear Plexiglas training chamber (20 cm tall, 15 cm deep, and 8.5 cm wide, measured from outside, with the thickness of the Plexiglas 0.5 cm) that contains three vertical slits (o.......

Discussion

Importance of the shaping phase:

Because of increased anxiety from being in an unknown environment, it is usually difficult for mice to be trained in a novel environment^21,22. Therefore, the goal of shaping is to familiarize mice with the training chamber, the trainer (i.e. reduce their anxiety levels), and the task requirements (i.e. to identify seed as food source). Another goal of the shaping is to determine the preferred limbs of individual mice for.......

Materials

Name	Company	Catalog Number	Comments
Training chamber in clear acrylic box	For dimensions, see Fig. 1A
Tilted tray for shaping	custom-made from glass slides, see Fig. 1B
Food platform for training	For dimensions, see Fig. 1C
Millet seeds	filtered from “Wild Bird Food Dove and Quail Blend Wild Bird Food (All Living Things)
Forceps	For placing the seeds
A weighing scale	For daily body weight measurement
A stopwatch	For time measurement during shaping/training sessions