This protocol is adapted from previous work within our lab (Huang et al.8). All methods described here have been approved by the Animal Care and Use Committee (ACUC) of Baylor College of Medicine. It is supported by the McNair Medical Institute, NINDS grant R01NS078294 to B.R.A., NIH IDDRC grant U54HD083092, NIDDK grant F30DK112571 to JMP, and NINDS grant F31NS092435 to CKM.

All mice were used under a protocol approved by the Baylor College of Medicine Institutional Animal Care and Use Committee in accordance with NIH standards. Mice used in this protocol were all adult mice (&#62;6 weeks of age) on C57BL6/j background and included both male and female mice.After training/staging tasks, mice are returned to their home cage.
1. Construction and General Rules for Using Operant Learning Box (Figure 1B, C)
<ol>
	<li>Assemble a mouse chamber with chamber floor. Keep the training box in a low traffic, dimly lit area to avoid distractions.</li>
	<li>Drill each water port with a small hole on top to allow an 18-gauge needle to dispense water inside the port.</li>
	<li>Fill glass vial with odorant dissolved in mineral oil (replaced weekly), and securely tighten the cap.</li>
	<li>Connect 18-gauge needle to silicone tubing. Pierce glass vial cap with 18-gauge needle, and connect other end of silicone tubing to the intake of the odor ports.</li>
	<li>Place each silicone tubing into an odor valve.</li>
	<li>Connect the vacuum line to the odor ports.</li>
	<li>Attach two 10 mL syringes to a metal holding rod, and connect tubing to the syringes. Connect the other side of the tubing to an 18 G needle. Fit the needle into the drilled hole of the nose poke port on the mouse chamber. Connect the other end of the tubing to the water valve.</li>
	<li>Fill the two 10 mL syringes with rodent drinking water.</li>
	<li>Connect an air-flow meter to the air intake and maintain air flow at 3&#8211;5 L/min.</li>
	<li>Connect the 2 water valves, 2 odor valves, 2 water ports, odor port, and power to the USB interface system. Connect all valves to &#39;Output&#39; ports, all the odor and water ports to &#39;Input&#39; ports. Connect all equipment to power outputs from the USB interface box, and lastly, connect the USB interface box to power.</li>
	<li>Adjust the vacuum suction to avoid cross contamination of odors between trials.</li>
	<li>Use odor-specific tubing to connect odorant vials to the chamber.</li>
</ol>
2. Mouse Preparation: 1&#8211;3 days
<ol>
	<li>Divide mice into 3 groups: control (no olfactory training necessary), pseudo-trained (mice who receive reward or punishment at random), and trained groups. Expose pseudo-trained mice to the training box and odor delivery, but do not provide olfactory training because the outcome of reward versus punishment is randomly associated with the odor delivered. 
	NOTE: The pseudo-trained group will go through the training paradigm under the &#34;Pseudotraining&#34; stages. Trained mice will complete all training stages. Pseudotraining is optional if the purpose of the experiment is to assay for behavioral differences in odor discrimination or learning. The protocol provided here adds this group if the experimenter wants to probe for neuronal differences before and after training. The pseudotrained group would then control for passive odor exposure and non-olfactory related training.</li>
	<li>Begin water restriction in mice to 40 mL/kg/day. Avoid bodyweight loss greater than 20% of the animals&#39; baseline weight in order to avoid distress (Figure 2A).</li>
	<li>Weigh the mice daily to ensure they are above 80% of baseline weight. If a mouse falls below this threshold, remove the mouse from the study and provide free access to water.</li>
	<li>Keep all environmental factors constant throughout the protocol including temperature, noise, and stray odors (including personal body and perfume/cologne/deodorant scents). 
	NOTE: As with all animal behavior testing, small environmental changes can greatly influence results.</li>
</ol>
3. Instructions for All Stages
<ol>
	<li>Code training software for each stage below. Run the software on the behavioral software. 
	NOTE: Coding for all stages are contained in supplemental coding files. Data for 20 trails are grouped as a single block and mouse performance is displayed across blocks. Furthermore, each stage can be repeated on a mouse for a number of days until completion criteria are met.</li>
	<li>Do not keep mice in the behavior box for more than 60 min/day.</li>
	<li>Clean mouse waste from the cage before each mouse is transferred to the cage. Spray and wipe the chamber with 70% ethanol to minimize mouse odor distraction.</li>
</ol>
4. Training Stage 1: Associating Water Reward with a Center Nose Poke, 1&#8211;3 Days
<ol>
	<li>In this stage, associate mice with a water reward upon exploration of the water port.</li>
	<li>Training Stage 1 programming instructions
	<ol>
		<li>Program this stage to only use the water delivery port. Let the mouse receive a water reward for each nose poke. 
		NOTE: The program will output the time duration of the trial and the total number of water rewards the mouse received.</li>
	</ol>
	</li>
	<li>Set the pseudotraining Stage 1 programming the same as Training Stage 1.</li>
	<li>Box configuration and mouse setup
	<ol>
		<li>Configure the behavior box with a water port in the center and with all side ports inaccessible. Place a mouse into the chamber. Close the mouse chamber and begin the Stage 1 program.</li>
	</ol>
	</li>
	<li>Consider this stage as complete when the mouse achieves 100 trials within 60 min. Remove the mouse from the chamber after 60 min or 100 trials have been completed (Figure 2B). 
	NOTE: Due to individual differences, some mice will naturally refrain from exploring the box.</li>
	<li>If encouragement is needed, manually deliver water into the water port. Repeat this stage for up to 3 days. 
	NOTE: Mice that are already trained can be repeated further to maintain parity and to keep them on fluid restriction. It is also possible to promote an entire group to stage 2 when the group average reaches 100 trials/60 min. This will allow for all mice to continue training on the same day.</li>
</ol>
5. Training Stage 2: Associating a Side Port Water Reward with Center Port Nose Poke, 1&#8211;5 Days
<ol>
	<li>In this stage, let the mice poke their nose in the center port and then immediately receive a water reward on the side ports.</li>
	<li>Box configuration and mouse setup
	<ol>
		<li>Configure this and every subsequent stage with 2 water ports on the sides and the odor port in the middle. Place a mouse into the chamber. Close the mouse chamber and begin the Stage 2 program.</li>
	</ol>
	</li>
	<li>Training Stage 2 programming instructions
	<ol>
		<li>Provide the mouse with an immediate water reward on both sides after a nose poke into the center odor delivery port. Set output parameters for this stage as the time duration of the trial, the number of trials initiated, and the number of water rewards received within 5 s of a nose poke.</li>
	</ol>
	</li>
	<li>Set the pseudotraining Stage 2 programming the same as Training Stage 2.</li>
	<li>Consider this stage as complete when a minimum of 40 trials are performed in 60 min, with at least 25% of water rewards received within 5 s of the center port nose poke. Remove the mouse once this stage has completed (Figure 2C). 
	NOTE: The training program calculates the percentage of water rewards received in a timely manner in order to determine completion of this stage. Although mice vary in how fast they complete this stage, most mice will reach completion criteria within 5 days. However, if a mouse has not completed this stage within 5 days, do not advance the mouse to the next stage. This mouse will be removed from the cohort.</li>
</ol>
6. Training Stage 3: Associating a Water Reward with a Specific Odor and Within a Specific Time Window, 1&#8211;3 Days
<ol>
	<li>In this stage, let the mice receive a Go (S+) odor upon a nose poke in the center port. Subsequently, yield a water reward upon a nose poke into the side water ports within 5 s.</li>
	<li>Training Stage 3 programming instructions
	<ol>
		<li>Deliver the S+ odor in the center odor port.</li>
		<li>Deliver the water reward if the mouse pokes the side ports within 5 s of an odor delivery. 
		NOTE: The program begins by only requiring a 100 ms nose poke in the center port to yield a water reward. Once the mouse pokes the center port for correct amount of time in 80% of trials, the time duration of a nose poke required for a water reward will increase by 50 ms up to 400 ms.</li>
		<li>Set the output parameters identical to stage 2.</li>
	</ol>
	</li>
	<li>Set the pseudotraining Stage 3 programming instructions the same as Training Stage 3. However, do not connect the S+ odor to the odor delivery controller to ensure that the S+ odor is not associated with a water reward.</li>
	<li>Box configuration and mouse setup
	<ol>
		<li>Set the same configuration at stage 2.</li>
		<li>Connect the S+ odor to the odor delivery controller. Place a mouse into the chamber. Close the mouse chamber and begin the Stage 3 program. Remove the mouse once this stage has completed.</li>
	</ol>
	</li>
	<li>Consider this stage as complete when there are greater than 60 rewards within 60 min (Figure 2D).</li>
</ol>
7. Stage 4A: Associating No-Go (S-) Odor and Time-out Punishment, 1&#8211;2 Days
<ol>
	<li>In this stage, introduce the mice to a No-Go odor (S-). Provide a time out punishment to the mice that incorrectly go to the water ports after smelling the no-go odor.</li>
	<li>Training Stage 4A programming instructions
	<ol>
		<li>Deliver only the S+ odorant in this stage in the beginning, identical to stage 3. After mice complete 40 trials, begin random delivery of the odors to include both S+ and S- odors. Program a 2-s time out punishment if the mouse attempts to seek a water reward after being presented the No-Go odor. 
		NOTE: To aid in distinguishing Go vs. No-Go, the IR side lights can be manipulated such that they are on during Go odorants and off during No-Go odorants. The lights act as a secondary cue to aid mice in initial training. Once mice are trained with the lights, they should under-go training without lights to confirm they have learned the task with odors.</li>
		<li>Set the output parameters as time duration of the trial, number of trials initiated, number of trials completed, % correct, and total number of rewards received.</li>
	</ol>
	</li>
	<li>Set the pseudotraining Stage 4A programming instructions the same as Training Stage 4S except S+ and S- odors are presented randomly from the start. Give water reward or timeout punishments at random, regardless of task performance.</li>
	<li>Box configuration and mouse setup
	<ol>
		<li>Set the box configuration the same as previous stage 3.</li>
		<li>Connect both S+ and S- odor to the odor delivery controller. Place a mouse into the chamber. Close the mouse chamber and begin the Stage 4A program. After the mice complete 40 trials, switch the program to randomly deliver the odors. Remove the mouse once this stage has completed.</li>
	</ol>
	</li>
	<li>Consider this stage as complete when there are 40 trials with &#62; 60% correct responses.</li>
</ol>
8. Stage 4B: Associating No-Go (S-) Odor and Time Out Punishment, 5&#8211;11 Days
<ol>
	<li>Training Stage 4B programming instructions
	<ol>
		<li>Make this stage identical to stage 4A, however the time out punishment for attempting a water reward after a S- odor is 4 s.</li>
	</ol>
	</li>
	<li>Set the pseudotraining Stage 4B programming instructions identical to stage 4A, however water reward and time out punishment are randomly delivered per trial.</li>
	<li>Box configuration and mouse setup
	<ol>
		<li>Set the box configuration the same as previous stage 4A.</li>
		<li>Connect both S+ and S- odor to the odor delivery controller. Place a mouse into the chamber. Close the mouse chamber and begin the Stage 4B program. Consider this stage complete when there are &#62;100 trials within 60 min with accuracy &#62;85% (Figure 2E)</li>
	</ol>
	</li>
	<li>Monitor the maximum and minimum percentage correct for each session to track each mouse&#39;s progress in this stage. Approximately 85-90% of mice reach completion criteria for this stage. Exclude mice that do not achieve completion of this stage for the Go/No-Go testing phase.</li>
	<li>(Optional) At the end of this stage, apply a reversal training, where the Go/No-Go odorants are switched on the odor vial platform. Ensure that the mice are not associating with another stimulus, such as the sound of the valves associated with the side ports.</li>
</ol>
9. Go/No-Go Assay Task: 1 Day, 20 Min per Mouse per Day
<ol>
	<li>Consider this as the final stage to determine accuracy of identifying odor associations and learning to discriminate odor pairs. 
	NOTE: Novel odorants are utilized for S+/S- to test how long animals take to learn new associations. Structurally similar odorant pairs are used to increase task difficulty. Examples include 1-Butanol vs. 1-Pentanol, Isoamyl Acetate vs. Isoamyl Butyrate, and + Carvone vs. - Carvone.</li>
	<li>Programming instructions
	<ol>
		<li>Let the training software detect the length of nose poke. Program a 300 ms nose poke in the center odor port to execute the task.</li>
		<li>Set the output parameters identical to stage 4B, except do not use any light guided cues.</li>
	</ol>
	</li>
	<li>Box configuration and mouse setup
	<ol>
		<li>Set the box configuration the same as previous stage 4B.</li>
		<li>Connect both S+ and S- odor to the odor delivery controller. Place a mouse into the chamber. Close the mouse chamber and begin the Stage Go/No-Go program. Expose the mice that have learned the olfactory learning task to novel pairs of chemically similar odors. 
		NOTE: Wildtype mice with adequate odor discrimination reach &#62;85% accuracy with novel odorants after approximately 10-20 blocks or 200-400 trials (Figure 3A).</li>
	</ol>
	</li>
</ol>

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The authors declare no conflicts of interest and no competing interests.

The rodent olfactory system provides a unique model to study sensory dependent plasticity. Here we present an olfactory learning paradigm to train mice to associate odorant pairs with either a reward or punishment. Through this learning task, downstream circuit changes can be studied in subsequent experiments (electrophysiology, in vivo neuronal imaging, etc.). Upon completion, mice will learn to perform a simple odor cued task to associate a water reward with one odor, and a timeout punishment with ano...

The mouse OB, where odor information first enters the central nervous system (CNS), provides an excellent model to study experience-dependent structural changes. OB circuity continually integrates adult-born neurons in an activity-dependent manner. Adult-born neuron precursors divide off from progenitors that line the subventricular zone adjacent to the lateral ventricles1. Upon migrating into the OB, these neuronal precursors either survive, differentiate, and integrate as inhibitory granule cells, or undergo apoptosis2. Selection for cell fate is influenced by olfactory activity, including olfactory learning3,4,5,6. After integration, learning-induced synaptic changes occur in granule cells during a two-week critical period7,8. Thus, assays for olfactory learning are useful for examining how experience-dependent plasticity influences structural and functional reorganization of a mature brain circuit.
This protocol offers one approach to olfactory training by using an operant conditioning paradigm. In this task, water-deprived mice are trained to associate one odor (the &#34;Go&#34; odor) with a water reward and another odor (the &#34;No-Go&#34; odor) with a trial timeout punishment. Mice progress through a graded series of training phases over the course of 2-4 weeks. When training is complete, mice respond to the Go or No-Go odor with discrete, corresponding behaviors (seeking a water reward on Go trials and not seeking the water reward on No-Go trials) (Figure 1A). After training is complete, mice can be further challenged with chemically similar odor pairs to test discrimination or become transitioned to studies investigating how olfactory learning alters the structure or function of the OB. Although odor discrimination tasks have been previously described, most rely on subjective measurements such as number of sniffs between two odorants9,10. Furthermore, the need for human scoring of such tasks is also time-intensive. The Go/No-Go olfactory learning task described in this protocol offers an unbiased, direct measurement of odor discrimination and olfactory learning.

<table><tbody><tr><td>Glass vial</td><td>Qorpak</td><td>GLC-01016</td><td></td></tr><tr><td>Silicon Tubing</td><td>Thermo Scientific</td><td>86000030</td><td></td></tr><tr><td>18 gauge needles</td><td>BD</td><td>305196</td><td></td></tr><tr><td>1-Butanol</td><td>Sigma Aldrich</td><td>437603</td><td></td></tr><tr><td>Propionic Acid</td><td>Sigma Aldrich</td><td>402907</td><td></td></tr><tr><td>Mouse Chamber</td><td>Med Associates</td><td>ENV-307W</td><td></td></tr><tr><td>Chamber Floor</td><td>Med Associates</td><td>ENV-307W-GFW</td><td></td></tr><tr><td>Water Port</td><td>Med Associates</td><td>ENV-313W</td><td>Need two</td></tr><tr><td>Odor stimulus</td><td>Med Associates</td><td>ENV-275</td><td>Contain 2 valves to gate odor delivery&amp;nbsp;</td></tr><tr><td>Odor Port</td><td>Med Associates</td><td>ENV-375W-NPP</td><td></td></tr><tr><td>USB Interface</td><td>Med Associates</td><td>DIG-703A-USB</td><td></td></tr><tr><td>Desktop Computer with Windows 2000, XP, Vista, or 7</td><td></td><td></td><td></td></tr><tr><td>Flow meter</td><td>VWR</td><td>97004-952</td><td></td></tr><tr><td>Behavioral software</td><td>Med Associates</td><td>SOF-735</td><td>This software, which runs each training stage, has now been replaced with Med-PC V</td></tr><tr><td>Data Transfer software</td><td>Med Associates</td><td>SOF-731</td><td>This software formats the data to Excel</td></tr><tr><td>Training Software</td><td>Med Associates</td><td>DIG-703A-USB</td><td>This software is used to program each training stage</td></tr><tr><td>Water Valve</td><td>Neptune Research</td><td>225P012-11</td><td>This valve is used to gate the water delivery. Need Two</td></tr><tr><td>Odor Valve</td><td>Neptune Research</td><td>360P012-42</td><td>This valve is used to gate the odor delivery. Need Two</td></tr></tbody></table>

an objective and reproducible test of olfactory learning and discrimination in mice

Olfaction is the predominant sensory modality in mice and influences many important behaviors, including foraging, predator detection, mating, and parenting. Importantly, mice can be trained to associate novel odors with specific behavioral responses to provide insight into olfactory circuit function. This protocol details the procedure for training mice on a Go/No-Go operant learning task. In this approach, mice are trained on hundreds of automated trials daily for 2&#8211;4 weeks and can then be tested on novel Go/No-Go odor pairs to assess olfactory discrimination, or be used for studies on how odor learning alters the structure or function of the olfactory circuit. Additionally, the mouse olfactory bulb (OB) features ongoing integration of adult-born neurons. Interestingly, olfactory learning increases both the survival and synaptic connections of these adult-born neurons. Therefore, this protocol can be combined with other biochemical, electrophysiological, and imaging techniques to study learning and activity-dependent factors that mediate neuronal survival and plasticity.

Once mice have learned the olfactory learning task, they can now associate novel odor pairs with reward and punishment. These trained mice normally begin with about 50% accuracy on the Go/No-Go task. The percentage correct can be plotted by trial block as a learning curve for novel odor pairs (Figure 3A). Within 10 block trials, which take most mice less than 30 min to perform, mice are able to correctly discriminate between odors with greate...

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An Objective and Reproducible Test of Olfactory Learning and Discrimination in Mice

Here, we train mice on an associative learning task to test odor discrimination. This protocol also allows for studies on learning-induced structural changes in the brain.

Olfaction is the predominant sensory modality in mice and influences many important behaviors, including foraging, predator detection, mating, and ...

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8.5K Views.  Baylor College of Medicine. Here, we train mice on an associative learning task to test odor discrimination. This protocol also allows for studies on learning-induced structural changes in the brain.

Video: An Objective and Reproducible Test of Olfactory Learning and Discrimination in Mice

Low-stress Route Learning Using the Lashley III Maze in Mice

Many behavior tests designed to assess learning and memory in rodents, particularly mice, rely on visual cues, food and/or water deprivation, or other aversive stimuli to motivate task acquisition. As animals age, sensory modalities deteriorate. For example, many strains of mice develop hearing deficits or cataracts. Changes in the sensory systems required to guide mice during task acquisition present potential confounds in interpreting learning changes in aging animals. Moreover, the use of aversive stimuli to motivate animals to learn tasks is potentially confounding when comparing mice with differential sensitivities to stress. To minimize these types of confounding effects, we have implemented a modified version of the Lashley III maze. This maze relies on route learning, whereby mice learn to navigate a maze via repeated exposure under low stress conditions, e.g. dark phase, no food/water deprivation, until they navigate a path from the start location to a pseudo-home cage with 0 or 1 error(s) on two consecutive trials. We classify this as a low-stress behavior test because it does not rely on aversive stimuli to encourage exploration of the maze and learning of the task. The apparatus consists of a modular start box, a 4-arm maze body, and a goal box. At the end of the goal box is a pseudo-home cage that contains bedding similar to that found in the animal&#x2019;s home cage and is specific to each animal for the duration of maze testing. It has been demonstrated previously that this pseudo-home cage provides sufficient reward to motivate mice to learn to navigate the maze1. Here, we present the visualization of the Lashley III maze procedure in the context of evaluating age-related differences in learning and memory in mice along with a comparison of learning behavior in two different background strains of mice. We hope that other investigators interested in evaluating the effects of aging or stress vulnerability in mice will consider this maze an attractive alternative to behavioral tests that involve more stressful learning tasks and/or visual cues.

The Lashley III maze is a route-learning task that does not rely on aversive stimuli or visual cues. It is thus a highly attractive option for evaluating learning and memory, especially in aging mice or otherwise where stress is a consideration.

Many behavior tests designed to assess learning and memory in rodents, particularly mice, rely on visual cues, food and/or water deprivation, or other ...

Testing for Odor Discrimination and Habituation in Mice

This video demonstrates a technique to establish the presence of a normally functioning olfactory system in a mouse. The test helps determine whether the mouse can discriminate between non-social odors and social odors, whether the mouse habituates to a repeatedly presented odor, and whether the mouse demonstrates dishabituation when presented with a novel odor. Since many social behavior tests measure the experimental animal&#8217;s response to a familiar or novel mouse, false positives can be avoided by establishing that the animals can detect and discriminate between social odors. There are similar considerations in learning tests such as fear conditioning that use odor to create a novel environment or olfactory cues as an associative stimulus. Deficits in the olfactory system would impair the ability to distinguish between contexts and to form an association with an olfactory cue during fear conditioning. 
In the odor habitation/dishabituation test, the mouse is repeatedly presented with several odors. Each odor is presented three times for two minutes. The investigator records the sniffing time directed towards the odor as the measurement of olfactory responsiveness. A typical mouse shows a decrease in response to the odor over repeated presentations (habituation). The experimenter then presents a novel odor that elicits increased sniffing towards the new odor (dishabituation). After repeated presentation of the novel odor the animal again shows habituation. This protocol involves the presentation of water, two or more non-social odors, and two social odors. In addition to reducing experimental confounds, this test can provide information on the function of the olfactory systems of new knockout, knock-in, and conditional knockout mouse lines.

This manuscript describes a protocol to examine the olfactory system of rodents. The olfactory habituation/dishabituation test will allow investigators to determine whether a mouse habituates to a repeatedly presented odor and whether the mouse demonstrates dishabituation when presented a novel odor.

This video demonstrates a technique to establish the presence of a normally functioning olfactory system in a mouse. The test helps determine whether the ...

Behavior

Simple and Computer-assisted Olfactory Testing for Mice

Olfaction is highly conserved among species and is required for reproduction and survival.
In humans, olfaction is also one of the senses that is affected with aging and is a strong predictor of neurodegenerative diseases. Thus, olfaction testing is used as a non-invasive diagnostic method to detect neurological deficits early on. In order to understand the mechanisms underlying olfactory network susceptibility, olfactory research in rodents has gained momentum in the past decade.
Here, we present a very simple, time efficient and reproducible olfactory testing method of innate odor perception and sensitivity in mice without the need of any prior food or water restriction. The tests are performed in a familiar environment to the mice, require only the scents and a 2 min session of odorant exposure. The analysis is performed, post-hoc, using computer-assisted commands on ImageJ and can be, therefore, carried out from start to end by one researcher.
This protocol does not require any special hardware or setup and is indicated for any laboratory interested in testing olfactory perception and sensitivity.

We present a simple and unbiased olfactory test in mice. With this protocol olfactory discrimination, preference, avoidance and sensitivity to a novel odor as compared to water can be assessed in single behavioral sessions. This method is indicated for a single experimenter and analysis is based on computer-assisted video processing.

Olfaction is highly conserved among species and is required for reproduction and survival.
In humans, olfaction is also one of the senses that is affected ...

Morris Water Maze Test for Learning and Memory Deficits in Alzheimer&#39;s Disease Model Mice

The Morris Water Maze (MWM) was first established by neuroscientist Richard G. Morris in 1981 in order to test hippocampal-dependent learning, including acquisition of spatial memoryand long-term spatial memory 1. The MWM is a relatively simple procedure typically consisting of six day trials, the main advantage being the differentiation between the spatial (hidden-platform) and non-spatial (visible platform) conditions 2-4. In addition, the MWM testing environment reduces odor trail interference 5. This has led the task to be used extensively in the study of the neurobiology and neuropharmacology of spatial learning and memory. The MWM plays an important role in the validation of rodent models for neurocognitive disorders such as Alzheimer&#x2019;s Disease 6, 7. In this protocol we discussed the typical procedure of MWM for testing learning and memory and data analysis commonly used in Alzheimer&#x2019;s disease transgenic model mice.

Morris Water Maze Test for Learning and Memory Deficits in Alzheimer's Disease Model Mice

The Morris Water Maze is a behavioral task to test hippocampal-dependent learning and memory. It has been widely used in the study of neurobiology, neuropharmacology and neurocognitive disorders in rodent models.

The Morris Water Maze (MWM) was first established by neuroscientist Richard G. Morris in 1981 in order to test hippocampal-dependent learning, including ...

Olfactory Behavioral Testing in the Adult Mouse

The rodent olfactory system is of increasing interest to scientists, studied, in part, in systems biology because of its stereotyped, yet accessible circuitry. In addition, this area's unique ability to generate new neurons throughout an organism's lifetime makes it an attractive system for developmental and regenerative biologists alike. Such interest necessitates a means for a quick, yet reliable assessment of olfactory function. Many tests of olfactory ability are complex, variable or not specifically designed for mice. Also, some tests are sensitive to memory deficits as well as defects in olfactory abilities, confounding obtained results.
Here, we describe a simple battery of tests designed to identify defects in olfactory sensitivity and preference. First, an initial general health assessment allows for the identification of animals suitable for further testing. Second, mice are exposed to various dilutions of scents to ascertain whether there is a threshold difference. Third, mice are presented with various scents, both attractive and aversive, that allow for the assessment of olfactory preference. These simple studies should make the initial characterization of olfactory behavior accessible for labs of varied resources and expertise.

Fundamental, yet unique properties of the rodent olfactory system have led to its increasing study among biologists. A relatively simple assessment of its function is then also needed. Here we describe sensitive tests for the characterization of mouse olfactory sensitivity and preference.

The rodent olfactory system is of increasing interest to scientists, studied, in part, in systems biology because of its stereotyped, yet accessible ...

Biology

A Low-Cost, Odor-Reward Association Task for Tests of Learning and Memory

Robust and simple behavioral paradigms of appetitive, associative memory are crucial for researchers interested in cellular and molecular mechanisms of memory. In this paper, an effective and low-cost mouse behavioral protocol is described for examining the effects of physiological manipulation (such as the infusion of pharmacological agents) on the learning rate and duration of odor-reward memory. Representative results are provided from a study examining the differential role of tyrosine kinase receptor activity in short-term (STM) and long-term memory (LTM). Male mice were conditioned to associate a reward (sugar pellet) with one of the two odors, and their memory for the association was tested 2 or 48 h later. Immediately prior to the training, a tyrosine kinase (Trk) receptor inhibitor or vehicle infusions were delivered into the olfactory bulb (OB). Although there was no effect of the infusion on the learning rate, blockade of the Trk receptors in the OB selectively impaired LTM (48 h), and not short-term memory (STM; 2 h). The LTM impairment was attributed to the diminished odor selectivity as measured by the length of the digging time. The culmination of the results of this experiment showed that Trk receptor activation in the OB is the key in olfactory memory consolidation.

An odor-reward, associative learning task was used to investigate the differential effects of physiological manipulation on long-term and short-term memory.

Robust and simple behavioral paradigms of appetitive, associative memory are crucial for researchers interested in cellular and molecular mechanisms of ...

Assessing Olfactory Impairment in Mice Due to Inhaled Environmental Pollutants

Studying the Effects of Inhaled Environmental Pollutants on Olfactory Function in Mice

Olfactory impairment is a significant public health problem and independently predicts the risk of neurodegenerative diseases. Inhaled environmental pollutants exposure may impair olfaction; thereby, there is an urgent need for methods to evaluate the effects of inhaled environmental pollutants exposure on olfaction. Mice are ideal models for olfactory experiments because of their highly developed olfactory system and behavioral characteristics. To assess the effects of inhaled environmental pollutants exposure on olfactory function in mice, a detailed buried food test and social odor discrimination experiment is provided, including the experiment preparation, the selection and construction of experimental facilities, the testing process, and indexes of time. Meanwhile, timekeeping equipment, operational details, and the experimental environment are discussed to ensure the success of the assay. Zinc sulfate is used as the treatment to demonstrate the feasibility of the experimental approach. The protocol provides a simple and clear operational process for assessing the effects of inhaled environmental pollutants on olfactory function in mice.

Author Spotlight: Assessing the Olfactory Effects of Airborne Pollutants &#8212; Buried Food and Social Odor Tests

This paper provides a detailed description of the buried food test and social odor discrimination experiment to assess the effects of inhaled environmental pollutants exposure on olfactory function in mice.

Olfactory impairment is a significant public health problem and independently predicts the risk of neurodegenerative diseases. Inhaled environmental ...

Environment

Assessment of Mouse Judgment Bias through an Olfactory Digging Task

Judgment biases (JB) are differences in the way that individuals in positive and negative affective/emotional states interpret ambiguous information. This phenomenon has long been observed in humans, with individuals in positive states responding to ambiguity 'optimistically' and those in negative states instead showing 'pessimism'. Researchers aiming to assess animal affect have taken advantage of these differential responses, developing tasks to assess judgment bias as an indicator of affective state. These tasks are becoming increasingly popular across diverse species and fields of research. However, for laboratory mice, the most widely used vertebrates in research and a species heavily relied upon to model affective disorders, only one JB task has been successfully validated as sensitive to changes in affective state. Here, we provide a detailed description of this novel murine JB task, and evidence of its sensitivity to mouse affect. Though refinements are still necessary, assessment of mouse JB opens the door for answering both practical questions regarding mouse welfare, and fundamental questions about the impact of affective state in translational research.

This article provides a detailed description of a novel mouse judgment bias protocol. Evidence of this olfactory digging task's sensitivity to affective state is also demonstrated and its utility across diverse research fields is discussed.

Judgment biases (JB) are differences in the way that individuals in positive and negative affective/emotional states interpret ambiguous information. This ...

Olfactory Assays for Mouse Models of Neurodegenerative Disease

In many neurodegenerative diseases and particularly in Parkinson&#8217;s disease, deficits in olfaction are reported to occur early in the disease process and may be a useful behavioral marker for early detection. Earlier detection in neurodegenerative disease is a major goal in the field because this is when neuroprotective therapies have the best potential to be effective. Therefore, in preclinical studies testing novel neuroprotective strategies in rodent models of neurodegenerative disease, olfactory assessment could be highly useful in determining therapeutic potential of compounds and translation to the clinic. In the present study we describe a battery of olfactory assays that are useful in measuring olfactory function in mice. The tests presented in this study were chosen because they measure olfaction abilities in mice related to food odors, social odors, and non-social odors. These tests have proven useful in characterizing novel genetic mouse models of Parkinson&#8217;s disease as well as in testing potential disease-modifying therapies.

Impairment in olfactory function is a common feature in many neurodegenerative disorders including Parkinson, Alzheimer, and Huntington diseases. In the present article, we describe a set of tests for assessing olfaction discrimination and detection in mice that can be used to measure olfactory abilities in mouse models of neurodegenerative diseases.

In many neurodegenerative diseases and particularly in Parkinson&#8217;s disease, deficits in olfaction are reported to occur early in the disease process ...

Designing a Flexible, Cost-Effective Olfactometer for Rodent Olfactory Experiments

Constructing an Olfactometer for Rodent Olfactory Behavior Studies

The use of olfactometers to study rodent behavior and brain activity during olfactory tasks is crucial for understanding brain circuits. These sophisticated devices allow researchers to precisely control and deliver odor stimuli, enabling the investigation of complex olfactory processes in rodents. Although commercially available olfactometers are convenient, they present challenges when technical issues arise, often requiring costly assistance and potentially disrupting research timelines. This article details the construction of a custom olfactometer specifically designed for mouse olfactory behavior experiments, providing a comprehensive list of parts and step-by-step instructions. The olfactometer is controlled through MATLAB, offering a user-friendly interface for researchers. Importantly, the open-source code allows users to modify and adapt the system, tailoring behavioral tasks to meet specific experimental needs. Building a customized olfactometer empowers users with the knowledge and capability to perform custom experimental design and troubleshooting independently, saving both time and resources. This approach not only enhances research flexibility but also fosters a deeper understanding of the equipment's functionality, ultimately leading to more robust and reliable olfactory studies in rodents.

Constructing an Olfactometer for Rodent Olfactory Behavior Studies Near-Infrared Spectroscopy Hyperscanning Study in Psychological Counseling

This protocol describes the construction of an olfactometer for go/no-go olfactory behavior experiments. Step-by-step instructions, along with images, are provided to ensure the successful construction of the olfactometer. Information for troubleshooting issues encountered during the process is also included.