Name: Study Motor Skill Learning by Single-pellet Reaching Tasks in Mice (Video) | JoVE Journal
Uploaded: 2014-03-04T17:05:00.000+00:00
Duration: 6 min 4 s
Description: Learn single-pellet reaching tasks to assess motor skill learning and memory in mice. This behavioral paradigm evaluates forelimb coordination precision through persistent practice and helps researchers study neural mechanisms underlying skill acquisition.

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5 minutes

This work is supported by a grant (1R01MH094449-01A1) from the National Institute of Mental Health to Y.Z.&#160;

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)
<ol>
	<li>Use millet seeds as food pellets.</li>
	<li>Use a custom-made clear Plexiglas&#160;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 (one slit on &#39;shaping&#39; edge, and two slits on the opposite &#39;training&#39; edge). The vertical slits should be 0.5 cm wide and 13 cm tall and be located on the front wall of the box: in the center, on the left side, and on the right side (Figure 1A).</li>
	<li>Use a tilted tray to hold the seeds used during shaping sessions. The tray can be custom-made from three glass slides (Figure 1B).</li>
	<li>Prepare a food platform (8.5 cm long, 4.4 cm wide, and 0.9 cm tall). This food platform is placed in the front side (facing the trainer) of the training chamber during training sessions. There are two divot slots on the food platform for positioning seeds, one slot on the left, and the other slot on the right side. The divots are 0.3 cm from the long edge, and 2.4 cm from the width edge (Figure 1C). The left and right divot slots correspond to the left and right slit in the mouse training chamber and are used for training of dominant forelimbs. The purpose of having these divot slots is to ensure that the seed is placed consistently at the same place for each reaching attempt.</li>
	<li>During sessions have in hand a pair of forceps, weighing scale, and stopwatch.</li>
</ol>
2. Food Deprivation (2 Days)
<ol>
	<li>Weigh each mouse to obtain a baseline bodyweight before food deprivation.</li>
	<li>Food-restrict mice for 2 days to initiate bodyweight loss. As a general starting point, mice are given 0.1 g of food per 1 g bodyweight per day (e.g.&#160;a mouse weighing 15 g, we usually start with 1.5 g of food). Adjust the amount of food based on the baseline bodyweight, the rate of weight loss, sex, and age of mice. While the bodyweight may continue to decrease a little more during the shaping phase, such reduced body weight (i.e.&#160;~90% of the original baseline weight) should be maintained throughout training (Figures 2A and 2B). The amount of food necessary to maintain the mouse&#39;s body weight is typically the same as the amount used in restriction.</li>
</ol>
3. Shaping (3-7 Days)
<ol>
	<li>Group habitat acclimatization (Day 1): Put two mice into the training chamber at the same time. Place approximately 20 seeds/mouse inside the chamber for their consumption. Allow the mice to stay in the chamber for 20 min and then put them back into their home cage.</li>
	<li>Individual habitat acclimatization (Day 2): The same setup as in step&#160;3.1, but place mice into the training chamber individually. The purpose of group and individual habitat acclimatization is to get the mice familiar with both the training chamber and the millet seeds.</li>
	<li>Determination of forelimb dominance (Day 3 and later): Place the single slit side of the training chamber facing downwards (Figure 1D). Fill the food tray with seeds. Press the food tray up against the front wall of the training chamber to allow the seeds accessible to the mouse. Place mice into the cage individually. If they are sufficiently interested in the seeds located on the food tray, they would plow through the slit to get the seed inside. They will then pick up the seeds and consume them. &#39;Shaping&#39; is considered finished when both of the following criteria are met: 1) the mouse conducts 20 reaching attempts within 20 min, and 2) more than 70% reaches are performed with one forelimb.</li>
</ol>
Notes:
<ol>
	<li>If the mouse uses its tongue to get the seeds into the chamber, move the tray back from the slit slightly. The increase in reaching distance discourages the mouse to use its tongue to acquire the seed and therefore facilitates its forelimb reaching.</li>
	<li>If the mouse cannot finish shaping within a week, drop it from the experiment.</li>
</ol>
4. Training (8+ Days)
<ol>
	<li>Place the double-slit side of the training chamber facing downwards (Figure 1E).</li>
	<li>Place the mice in the cage individually. Put individual seeds on the food platform in the divot corresponding to the preferred paw (i.e.&#160;for the right-handed mouse, use the slit on the mouse&#39;s right side).</li>
	<li>Observe mouse reaching behavior and score according to the following categories:
	<ol>
		<li>Success: The mouse reaches with preferred paw, grasps and retrieves the seed, and feeds it into its mouth.</li>
		<li>Drop: The mouse reaches with preferred paw, grasps the seed, but drops it before putting it into its mouth.</li>
		<li>Fail: The mouse reaches with preferred paw towards the seed, but it either misses the seed or knocks it off from the holding plate.</li>
	</ol>
	</li>
	<li>Train the mice for 30 reaching attempts on the preferred limb or 20 min (whichever comes first) per day.</li>
	<li>Place the mice back to their home cage after training and provide daily food quantum.</li>
</ol>
Notes:
<ol>
	<li>In some cases, mice reach even when there is no seed placed on the food platform. Such reaches are considered &#34;in-vain reaches&#34; and are not counted towards the total number of reaching attempts. To discourage &#34;in-vain reaches&#34;, train mice to walk back to the other end of the training chamber before placing the next seed. A similar strategy has been used in rats for a similar behavioral task21. Mice sometimes also reach with nonpreferred paw in the presence of the seed. These reaches are considered &#39;contralateral reaches&#39; and do not count&#160;towards the total number of reaches either.</li>
	<li>To limit behavioral variations due to the fluctuations in circadian rhythm, perform all shaping and training sessions at the same time of the day, during normal waking hours for mice.</li>
	<li>To avoid &#160;behavioral variation due to different trainers, make sure the same person trains the same mice throughout the experiment.</li>
	<li>Attention of mice is critical for this behavioral test. Train mice in a separate and quiet room to minimize environmental perturbation.</li>
	<li>Mice can be trained with more than 30 reaches daily (e.g.&#160;50 reaches). Increasing the number of reaching attempts makes it possible to examine behavioral improvement within the same training session.</li>
</ol>
5. Data Quantification
There are many ways to quantify mouse behavior following training. Two most straight-forward analyses are:
<ol>
	<li>Success rate = successful reaches over total reaching attempts, presented as percentages. Drop and failure rates can be plotted the same way.</li>
	<li>Speed of success = number of successful attempts divided by time, presented as successful reaches per minute. In most cases, the speed of success continues to increase, even when the success rate attains the plateau.</li>
</ol>

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The authors declare no conflict of interest.

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 environment21,22. Therefore, the goal of shaping is to familiarize mice with the training chamber, the trainer&#160;(i.e.&#160;reduce their anxiety levels), and the task requirements (i.e.&#160;to identify seed as food source). Another goal of the shaping is to determine the preferred limbs of individual mice for...

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 tomography (PET) and functional magnetic resonance imaging (fMRI) have shown that primary motor cortex (M1) activity changes during the acquisition phase of motor skill learning2-4, and temporary interference of M1 activity by low frequency transcranial magnetic stimulation leads to significantly disrupted retention of motor behavioral improvement5. Similarly, forelimb-specific training in rats induces functional and anatomical plasticity in the M1, exemplified by the increase of both c-fos activity and synapse/neuron ratio in the M1 contralateral to the trained forelimb during the late phase of motor skill learning6. Furthermore, a similar training paradigm also strengthens layer 2/3 horizontal connections in the contralateral M1 corresponding to the trained forelimb, resulting in reduced long term potentiation (LTP) and enhanced long term depression (LTD) after rats acquire the tasks7. Such synaptic modification, however, is not observed in the M1 cortical regions corresponding to untrained forelimb or hindlimbs8. Alternatively, when the M1 is damaged through stroke, there are dramatic deficiencies in forelimb specific motor-skills9. While most of the motor behavioral studies have been conducted on humans, monkeys, and rats2-8,10-17, mice become an attractive model system because of its powerful genetics and low cost.
Here we present a forelimb specific motor-skill learning paradigm: a single-pellet reaching task. In this paradigm, mice are trained to extend their forelimbs through a narrow slit to grasp and retrieve food pellets (millet seeds) positioned at a fixed location, a behavior analogous to learning archery, dart-throwing, and shooting basketballs in human. This reaching task has been modified from previous rat studies that have shown similar results between mice&#160;and rats18. Using two-photon transcranial imaging, our previous work has followed the dynamics of dendritic spines (postsynaptic structures for majority excitatory synapses) over time during this training. We found that a single training session led to rapid emergence of new dendritic spines on pyramidal neurons in the motor cortex contralateral to the trained forelimb. Subsequent training of the same reaching task preferentially stabilized these learning-induced spines, which persisted long after training terminated19. Furthermore, spines that emerged during repetitions of reaching task tended to cluster along dendrites, whereas spines formed during tandem execution of reaching task and another forelimb-specific motor task (i.e.&#160;the pasta handling task) did not cluster20.
In the present video, we describe step-by-step the setup of this behavioral paradigm, from the initial food deprivation to shaping, and to motor training. We also describe the common behaviors of mice during the process of executing this behavioral paradigm, and how these behaviors are categorized and analyzed. Finally, we discuss the precautionary measures needed to practice such a learning paradigm and the issues that may be encountered during data analyses.

<table><tbody><tr><td>Training chamber in clear acrylic box</td><td></td><td></td><td>For dimensions, see &lt;strong&gt;Figure 1A&lt;/strong&gt;</td></tr><tr><td>Tilted tray for shaping</td><td></td><td></td><td>Custom-made from glass slides, see &lt;strong&gt;Figure 1B&lt;/strong&gt;</td></tr><tr><td>Food platform for training</td><td></td><td></td><td>For dimensions, see &lt;strong&gt;Figure 1C&lt;/strong&gt;</td></tr><tr><td>Millet seeds&amp;nbsp;</td><td></td><td></td><td>Filtered from &amp;ldquo;Wild Bird Food Dove and Quail Blend Wild Bird Food&amp;rdquo; (All Living Things)</td></tr><tr><td>Forceps</td><td></td><td></td><td>For placing the seeds</td></tr><tr><td>A weighing scale</td><td></td><td></td><td>For daily body weight measurement</td></tr><tr><td>A stopwatch</td><td></td><td></td><td>For time measurement during shaping/training sessions</td></tr></tbody></table>

study motor skill learning by single-pellet reaching tasks in mice

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

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.

Learning curve:
Mastery of a motor skill often requires persistent practice over time. A typical averaged learning curve is composed of two phases: an initial acquisition phase during which the success rate improves progressively, and a later consolidation phase when the success rate reaches the plateau (Figure 2C). It should be noted the learning curves of individual mice vary; different mice take different numbers of days to reach the plateau level, and the individual learning ...

Persistent practice improves the precision of coordinated movements.&#160;Here we introduce a single-pellet reaching task, which is designed to assess the learning and memory of forelimb skill in mice.&#160;

Reaching for and retrieving objects require precise and coordinated motor movements in the forelimb. When mice are repeatedly trained to grasp and ...

The overall goal of this procedure is to train mice with a four M specific motor skill. This provides a good behavioral model to assess motor learning and memory. In mice, the first step is to allow mice to become familiar with the training chamber and food pellets.Next food pellets are put within reach of the shaping slit, and the preferred for limb used for retrieval is determined after the shaping period. The mice are trained with the single pellet reaching task and the number of correct reaches with the preferred paw is recorded. Ultimately, this protocol provides a behavioral paradigm to study brain changes at many levels during motor learning and memory formation.This method can help answer key questions in the neuroscience field, such as how motor learning correlates with structural plasticity and molecular alterations in the mouse brain, and how various neurological diseases perturb fine motor skills For the best results. Perform this task in a quiet location away from any noise or distractions. A custom made clear plexiglass training chamber that contains three vertical slits is used for shaping and training.One slit is on the shaping edge and two slits are on the opposite training edge to hold the millet seeds in place during the shaping sessions constructed a tilted tray from three glass slides. A food platform is used during the training sessions. Divots on the left and right sides of the platform hold the millet seed in place.These divots correspond to the left and right slit in the mouse training chamber and are used for the training of dominant for lims. Other items useful to have on hand during the procedure are forceps, a scale and a stopwatch. Two days before beginning the shaping procedure food restrict the animals to maintain a reduced body weight of about 90%of baseline on day one.Placed two mice into the training chamber at the same time, and allow them to habituate. Place approximately 20 mil seeds per mouse inside the chamber and allow the mice to explore for 20 minutes. On the next day, place the animals into chambers individually and provide each with approximately 20 mil seeds the following day.The shaping edge is used to determine for limb dominance. Place the single slit side of the chamber facing downwards. Next, press the food tray filled with millet seeds up against the front wall of the training chamber.When ready, place a single mouse in the chamber. Allow the animal to retrieve seed through the training slit and record the for used for the retrieval. The shaping period is considered finished when two criteria are met.First, the mouse conducts 20 reaching attempts within 20 minutes. Second, more than 70%of these reaches are performed with one four limb. If the mouse uses its tongue to get the seeds into the chamber, move the tray back slightly to encourage four limb reaching.If the mouse cannot finish shaping within a week, drop it from the experiment To begin the training session, configure the training chamber with the double slit face downwards. When ready, place the mice individually into the cage. Put individual seeds on the food platform in the divot corresponding to the preferred paw determined during the shaping period.Once the seed is in place, observe the mouse's reaching behavior and score the results. A success is scored when the mouse reaches with the preferred paw, retrieves and eats the seed. Score a drop when the mouse reaches with the preferred paw, grasps the seed, but drops it before putting it into its mouth.If the mouse reaches for the seed with the preferred paw, but either misses it or knocks it off the holding plate, it is scored as a fail. A mouse may reach even when there is no seed placed on the food platform. These are considered in vain reaches and are not counted towards.The total number of reaching attempts to discourage in vain reaches train mice to walk back to the other end of the training chamber before placing the next seed. If a mouse reaches with the non-preferred paw, these reaches are considered contralateral reaches and are not counted towards the total number of reaches. Train the mice daily for 30 reaching attempts on the preferred limb, or 20 minutes, whichever comes first.After the daily training session, return the mice to their home cage. Body weights of mice should be closely monitored throughout experiments. Body weight loss for a single mouse during food deprivation shaping and training is shown here.These results show that the average success rate improves over the training period as well as the average speed of success. Success rates for an overs shaped and a non learning mouse are plotted here. This graph compares the motor performance of pre-trained versus naive adult mice during a four day retraining period.While attempting this procedure, it's important to remember to standardize animal testing conditions. This can be done by minimizing environmental perturbations, having the same trainer, handling the same mouse, and training at the same hours within the day throughout the experiments.

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Research

JoVE Journal

Behavior

Learning new stimulus-response associations engages a wide range of neural processes which are ultimately reflected in changing spike output of individual neurons. Here we describe a behavioral protocol allowing for the continuous registration of single-neuron activity while animals acquire, extinguish, and reacquire a conditioned response within a single experimental session.

Recording Single Neurons' Action Potentials from Freely Moving Pigeons Across Three Stages of Learning

Mouse models have become increasingly popular in studies of behavioral neuroscience.  As models advance, it is important to develop sensitive behavioral measures specific to the mouse.  This protocol describes the Pasta Matrix Reaching Task, which is a skilled motor task for use in mouse models of stroke.

Compensatory Limb Use and Behavioral Assessment of Motor Skill Learning Following Sensorimotor Cortex Injury in a Mouse Model of Ischemic Stroke

A paradigm is presented to analyze the acquisition of a high-precision skilled forelimb reaching task in rats.

Acquisition of a High-precision Skilled Forelimb Reaching Task in Rats

A paradigm is presented for training and analysis of an automated skilled reaching task in rats. Analysis of pulling attempts reveals distinct subprocesses of motor learning.

Investigating Motor Skill Learning Processes with a Robotic Manipulandum

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.

Evaluating Skilled Prehension in Mice Using an Auto-Trainer

Rodent skilled reaching is commonly used to study dexterous skills, but requires significant time and effort to implement the task and analyze the behavior. We describe an automated version of skilled reaching with motion tracking and three-dimensional reconstruction of reach trajectories.

Automated Rat Single-Pellet Reaching with 3-Dimensional Reconstruction of Paw and Digit Trajectories

The present protocol describes how to use wireless optogenetics combined with high-speed videography in a single pellet reach-to-grasp task to characterize the neural circuits involved in the performance of skilled motor behavior in freely moving mice.

In Vivo Wireless Optogenetic Control of Skilled Motor Behavior

This article presents a protocol that allows a non-invasive and automated assessment of fine motor performance, as well as adaptive and associative motor learning upon challenges, using a device called the Erasmus Ladder. Task difficulty can be titrated to detect motor impairment ranging from major to subtle degrees.

Monitoring Fine and Associative Motor Learning in Mice Using the Erasmus Ladder

The current study describes a fine motor behavior test for examining motor deficits in rodent models, including the TgF344-AD rat, using machine learning.

A Fine Motor Task to Study Joint Kinematics in a Preclinical Model of Neurodegenerative Disease

Behavioral tasks that allow for the assessment of perceptual and sensorimotor timing abilities in the general population (i.e., non-musicians) are presented. Synchronization of finger tapping to the beat of an auditory stimuli and detecting rhythmic irregularities provides a means of uncovering rhythm disorders.

Uncovering Beat Deafness: Detecting Rhythm Disorders with Synchronized Finger Tapping and Perceptual Timing Tasks

Learn single-pellet reaching tasks to assess motor skill learning and memory in mice. This behavioral paradigm evaluates forelimb coordination precision through persistent practice and helps researchers study neural mechanisms underlying skill acquisition.

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

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