Evaluating Skilled Prehension in Mice Using an Auto-Trainer

Summary

Method to assess the impact of training on motor skills is a useful tool. Unfortunately, most behavioral assessments can be labor intensive and/or expensive.We describe here a robotic method of assessing prehension (reach-to-grasp) skill in mice.

Abstract

We describe a method to introduce naïve mice to a novel prehension (reach-to-grasp) task. Mice are housed singly in cages with a frontal slot that permits the mouse to reach out of its cage and retrieve food pellets. Minimal food restriction is employed to encourage the mice to perform the food retrieval from the slot. As the mice begin to associate coming to the slot for food, the pellets are manually pulled away to stimulate extension and pronation of their paw to grasp and retrieve the pellet through the frontal slot. When the mice begin to reach for the pellets as they arrive at the slot, the behavioral assay can be performed by measuring the rate at which they successfully grasp and retrieve the desired pellet. They are then introduced to an auto-trainer that automates both the process of providing food pellets for the mouse to grasp, and the recording of successful and failed reaching and grasping attempts. This allows for the collection of reaching data for multiple mice with minimal effort, to be used in experimental analysis as appropriate.

Introduction

Methods to experimentally test a motor skill pre- and post- neurological injury as well as modulate the timing, amount, and type of motor training are important to translational research. Over the last decade, mice, because of the attendant ease of genetic manipulation, have become a popular model system in which to elucidate the mechanisms of motor learning pre- and post- injury. However, behavioral assays in mice have not been optimized in the same way that such assays have been for other mammals (especially rats). Further, there are important differences between the behavior of a mouse and a rat that strongly suggest training the two species in different manners

Protocol

All methods described here have been approved by the ACUC (Animal Care and Use Committee) of the Johns Hopkins University.

1. Preparing mouse cages for use

1. Create a slotted opening with dimensions of 0.8 cm width and 7 cm height from the base at the front end of each cage, as illustrated in Figure 1. This slot serves as the opening through which the animal will reach.
   NOTE: The auto-trainer was designed for the use with the standard mouse cage dimensions (as shown in Figure 1) supplied by most animal research supply vendors. Further, the auto-trainer will easily ....

Results

In general, it is recommended that each training session consist of about 20-30 trials, which may be set by the user, run automatically by the auto-trainer and saved into a single log file per session and mouse. Each trial can be run consecutively, right after the other, with 2-5 s of pause. Mice trained on the auto-trainer exhibit an increase in skill over 10 training sessions.

To compare the utility of the auto-trainer to manu.......

Discussion

Our auto-trainer evaluates forelimb reach-to-grasp (prehension) in an automated manner. To achieve this endpoint, many of the parameters designed for the mouse prehension task, including pellet placement, pellet size, and training criteria, have been iterated over several years and adapted from prior protocols^2,5,6. The advancement here is the automation of the task using a robot that allows home-cage housing. Home-cage housing .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
ABS Filament	Custom 3D Printed	N/A	utilized for pellet holder, frame, arm and funnel
ABS Sheet	McMaster-Carr	8586K581	3/8" thickness; used for platform compononents, positioning stand guides and base
Adruino Mini	Adruino	A000087	nano version also compatiable as well as other similar microcontrollers
Bench-Top Adjustable-Height Positioning Stand	McMaster-Carr	9967T43	35 lbs. load capacity
Clear Acrylic Round Tube	McMaster-Carr	8532K14	ID 3/8"
Low-Carbon Steel Wire	McMaster-Carr	8855K14	0.148" diameter
Pellet Dispenser	Lafayette Instrument: Neuroscience	80209-45	with 45 mg interchangeable pellet size wheel and optional stand
Photointerrupter Breakout Board	SparkFun	BOB-09322 ROHS	designed for Sharp GP1A57HRJ00F
Reflective Object Sensor	Fairchild Semiconductor	QRD1113	phototransistor output
Servo Motor	SparkFun	S8213	generic metal gear (micro size)
Transmissive Photointerrupter	Sharp	GP1A57HRJ00F	gap: 10 mm, slit: 1.8 mm