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 (o...

<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 border="0" cellpadding="0" cellspacing="0" width="856">
	<colgroup>
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Training chamber in clear acrylic box</td>
			<td style="width:595px;">For dimensions, see Fig. 1A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Tilted tray for shaping</td>
			<td>custom-made from glass slides, see Fig. 1B</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Food platform for training</td>
			<td>For dimensions, see Fig. 1C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Millet seeds&#160;</td>
			<td>filtered from &#8220;Wild Bird Food Dove and Quail Blend Wild Bird Food (All Living Things)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Forceps</td>
			<td>For placing the seeds</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">A weighing scale</td>
			<td>For daily body weight measurement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">A stopwatch</td>
			<td>For time measurement during shaping/training sessions</td>
		</tr>
	</tbody>
</table>

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 ...

Watch this Scientific Journal Video about Study Motor Skill Learning by Single-pellet Reaching Tasks in Mice at JoVE.com

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

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 ...

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20.4K vistas.  University of California, Santa Cruz.  Práctica persistente mejora la precisión de los movimientos coordinados. Aquí se introduce una tarea de llegar a un solo gránulo, que está diseñado para evaluar el aprendizaje y la memoria de la extremidad anterior de habilidad en ratones. 