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Understanding Eyeblink Conditioning

Eyeblink conditioning is a form of classical conditioning where rabbits are trained to associate a conditioned stimulus (such as a tone or light) with an unconditioned stimulus (such as a puff of air to the eye), resulting in the rabbit blinking in response to the conditioned stimulus alone.

This type of conditioning requires the rabbit to learn the association between the stimuli through repeated pairings. As the training progresses, the rabbit’s blinking response becomes more precise and specific to the conditioned stimulus.

Understanding eyeblink conditioning is important as it provides insights into the mechanisms of learning and memory, and can be applied to various research areas.

Neural Mechanisms Involved

Eyeblink conditioning in rabbits involves complex neural mechanisms. The cerebellum plays a crucial role in this type of conditioning, as it is responsible for the coordination and timing of the eyeblink response.

Within the cerebellum, the interpositus nucleus and the cerebellar cortex are particularly important in mediating eyeblink conditioning. The interpositus nucleus receives the conditioned stimulus information and sends signals to the cerebellar cortex, which then relays the information to the facial motor nucleus to initiate the eyeblink response.

Other brain regions, such as the hippocampus and the amygdala, also contribute to the neural processes underlying eyeblink conditioning.

Applications in Research

Eyeblink conditioning in rabbits has been widely used in research to study various topics. It has been utilized to investigate the neural basis of learning and memory, as well as the effects of drugs and genetic manipulations on these processes.

Researchers have also applied eyeblink conditioning to study neurological disorders, such as cerebellar dysfunction and Alzheimer’s disease. By understanding the mechanisms involved in eyeblink conditioning, scientists can gain valuable insights into these conditions and potentially develop new therapeutic approaches.

Furthermore, eyeblink conditioning has been used to explore the impact of environmental factors, such as stress and aging, on learning and memory.

Training and Behavioral Modification

Training rabbits for eyeblink conditioning involves a series of steps to establish the association between the conditioned stimulus and the unconditioned stimulus.

Initially, the conditioned stimulus is presented simultaneously with the unconditioned stimulus, and the rabbit’s natural eyeblink response is reinforced. Over time, the conditioned stimulus is presented before the unconditioned stimulus, and the rabbit learns to anticipate the puff of air and blinks in response.

Behavioral modification techniques, such as shaping and reinforcement, are used to gradually shape the desired eyeblink response. Positive reinforcement, such as rewards or praise, is often employed to encourage the rabbit’s learning and performance.

Consistency and repetition are key in training rabbits for eyeblink conditioning, as it helps to strengthen the learned association and improve the precision of the eyeblink response.

Future Directions

The study of eyeblink conditioning in rabbits continues to advance our understanding of learning and memory processes.

Future research could focus on exploring the specific neural circuits and molecular mechanisms involved in eyeblink conditioning. By unraveling the intricacies of these mechanisms, scientists may uncover new targets for therapeutic interventions in conditions associated with learning and memory deficits.

Additionally, advancements in technology, such as optogenetics and neuroimaging techniques, can provide new tools to investigate eyeblink conditioning and its underlying neural processes.

Understanding eyeblink conditioning in rabbits may also have implications beyond the field of neuroscience. The principles of conditioning and behavioral modification can be applied to other species and utilized in various training and rehabilitation programs.

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The Locomotor Activity Test

Fundamentally, locomotor activity tests involve tracking an animal as it moves around an enclosed arena. These tests are commonly performed on rodents and capture ambulatory behavior by measuring metrics like speed, rest intervals, and distance traveled.3,4 Tracking is typically managed by either video-based or photobeam systems. Video tracking uses cameras sensitive to visible or infrared light to capture the subject’s movement, while photobeam setups employ infrared photoemitters and detectors to triangulate the animal’s location as it moves. Researchers may choose one method or use both for enhanced surveillance depending on experimental requirements.4

The collected data can be visualized through locomotor zone maps, which can be displayed as heat and density maps, to depict the subject’s travel path and time spent in specific sections. These locomotor zone maps provide invaluable insights into spatial perception and behavioral responses, advancing understanding of the subject’s locomotion and its interactions with the environment.4

Locomotor Activity Testing in Neuroscience and Psychopharmacology

The numerous facets of locomotor activity explain events occurring at the molecular level and the emergent properties of movement, motivation, and learning. For example, in a study aiming to understand the role of the D3 dopamine receptor in rodent locomotor behavior and its potential relevance to neuropsychiatric disease, the locomotor activity test enabled researchers to quantify the effects of D3 receptor agonists on mouse movement behavior. This helped establish that D3 receptor stimulation inhibits novelty-stimulated locomotion and provided conditions for in vivo administration of D3 receptor agonists.5

Locomotor activity tests have also been used to elucidate endogenous timing systems, downstream effects of genetic manipulation on locomotion, the impact and temporal importance of pharmacological substances on disease, and locomotor changes in neuropsychiatric conditions.6

Photobeam Tracking: The PAS-Home Cage and PAS-Open Field

San Diego Instruments (SDI) has pioneered cutting-edge technology in the field of locomotor activity testing, offering two systems that have revolutionized the way researchers study animal behavior – the Photobeam Activity System-Home Cage (PAS-HC) and the Photobeam Activity System (PAS)-Open Field.

The PAS-HC uses a 4×8 photobeam configuration to precisely capture and monitor the movement of mice or rats in their home cage environments. Real-time beam break reporting eliminates the need for specialized calibrators, ensuring accuracy in locomotor behavior measurement. In addition, the system’s sophisticated software enables comprehensive recording and analysis of diverse locomotor patterns, encompassing central peripheral activity, rearing, ambulation movements, and fine movements. The PAS-HC accommodates up to 48 test stations and can incorporate an optional rearing frame for up to 24 stations, providing flexibility and scalability.7

The PAS-Open Field provides researchers with a comprehensive toolkit for open field testing. It utilizes a 16×16 photobeam array to accurately track animal movement. The system’s advanced software enhances analysis by allowing pre-defined study parameters, automated test sessions, and real-time beam break displays. Notably, the PAS-Open Field can generate and utilize zone maps in both X and Y dimensions. This permits precise data analysis with customizable spatial divisions. The software further refines results by categorizing beam breaks into ambulations, fine movements, and rearing based on distance, enhancing result accuracy.8

A New Horizon in Locomotor Activity Testing

From its inception as the open field test to contemporary technologies like the PAS-HC and the PAS-Open Field, locomotor activity tests have catalyzed breakthroughs in neuroscience and psychopharmacology, revealing intricate links between genetic factors, environmental interactions, and drug effects on locomotion. Spearheading innovation, San Diego Instruments’ have empowered researchers to delve deeper into spatial perception, bridging the gap between behavior and neural mechanisms. As our understanding of locomotor activity expands, these tools continue to reshape our knowledge of how animals navigate their surroundings, forging a path towards enhanced therapeutic interventions and a deeper comprehension of the brain-body relationship.

References and Further Reading

1. Hall CS. (1934). Emotional behavior in the rat. I. Defecation and urination as measures of individual differences in emotionality. Journal of Comparative Psychology. https://doi.org/10.1037/h0071444
2. Choleris E, et al. (2001). A detailed ethological analysis of the mouse open field test: effects of diazepam, chlordiazepoxide and an extremely low frequency pulsed magnetic field. Neuroscience & Biobehavioral Reviews. https://doi.org/10.1016/S0149-7634(01)00011-2
3. Belovicova K, et al. (2017). Animal tests for anxiety-like and depression-like behavior in rats. Interdisciplinary Toxicology. https://doi.org/10.1515/intox-2017-0006
4. Behaviorcloud. (2019). [Webinar] Open Field Activity Tracking Webinar with BehaviorCloud & San Diego Instruments. Transcript available at: https://www.behaviorcloud.com/2019/07/17/Open-Field-Activity-Tracking-Webinar-with-BehaviorCloud-San-Diego-Instruments.html (Accessed on 08 August 2023).
5. Pritchard LM, et al. (2003). 7-OH-DPAT and PD 128907 Selectively Activate the D3 Dopamine Receptor in a Novel Environment. Neuropsychopharmacology. https://doi.org/10.1038/sj.npp.1300018
6. SD Instruments. What is the Locomotor Activity Test. Available at: https://sandiegoinstruments.com/what-is-the-locomotor-activity-test/ (Accessed on 09 August 2023).
7. SD Instruments. Photobeam Activity System-Home Cage. Available at: https://sandiegoinstruments.com/product/pas-homecage/ (Accessed on 09 August 2023).
8. SD Instruments. Photobeam Activity System-Open Field. Available at: https://sandiegoinstruments.com/product/pas-open-field/ (Accessed on 09 August 2023). 

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Neurodegenerative diseases, the progressive loss of brain and/or spinal cord neurons, are a major challenge to health systems across the globe. In some cases, neurodegenerative disorders are the second-most prevalent cause of death after cardiovascular diseases.1 Incidences of neurodegenerative diseases and resulting deaths are increasing with the current rapidly aging population. The most common neurodegenerative disorders are dementias, which affect around seven million people, and this estimation is predicted to double by 2040.2

The major problem with neurodegenerative disorders is that there is currently no cure or proper treatment because the mechanisms that cause them are not completely understood.3 There is, therefore, an urgent need to develop new, more effective, and safer treatments in neurodegenerative disease research, along with enhanced methods for earlier diagnosis.2

To this end, a tool that has proven indispensable in neurodegenerative disease research is the Morris Water Maze protocol. First described by Michael Morris in the 1980s, the Morris Water Maze is a universal protocol for testing normal cognitive function and can effectively detect any deviations in memory function.4

What is the Morris Water Maze experiment?

The Morris Water Maze experiment is a simple, spatial task for examining learning and memory in rodents. In the Morris Water Maze experiment, the rodent must swim in a tank to find a hidden platform using spatial cues memorized during pre-training.5 The assessment of the rodent’s spatial memory occurs within the framework of the Morris Water Maze protocol, where both the time it takes for the rodent to locate the platform and the efficiency of their direct route to the platform is observed.

The Morris Water Maze experiment can be used to compare the cognitive function of wild-type or neurodegenerative-prone rodents to identify the molecular mechanisms potentially underpinning these diseases; this method is regularly used in the study of Alzheimer’s disease (AD), for example.5 There are a range of different Morris Water Maze protocols which involve different mechanisms of navigation and can detect defects in the cognitive function of brain areas essential in learning and memory other than just the hippocampus.6

Understanding the progression and treatment of neurodegenerative diseases using the Morris Water Maze

Knowledge of the progression of neurodegenerative diseases is necessary for developing more effective treatments for these diseases. Morris Water Maze experiments have been used to evaluate the role of enzymes expressed in the brain that are involved in the progression of neuroinflammatory in AD. The role of the sEH enzyme in the development of AD was recently highlighted using the Morris Water Maze experiment, and research suggests that sEH is a vital regulator in the progression of AD and could be a potential therapeutic target for delaying the progression of AD.7

The Morris Water Maze experiments have been utilized to investigate the impact of overactive microglia on cognitive decline in Parkinson’s disease (PD). By assessing the cognitive performance of mice through this experiment, researchers explored the role of microglia in rotenone-induced cognitive deficits. The findings suggest that activated microglia contribute to cognitive impairments through processes like neuroinflammation, apoptosis, and oxidative stress. These new insights have significantly enhanced our understanding of the immunopathogenesis underlying cognitive defects in PD.

The significance of Morris Water Maze experiments also extends to exploring potential synergistic treatment approaches for enhanced effectiveness. A recent study exemplified this using the Morris Water Maze model to demonstrate the positive interactions between memantine and cholinesterase inhibitors. The combination of these treatments was found to be more effective than individual monotreatments, 9 providing valuable insights into potential complementary therapies.

Conclusion

Thanks to its simplicity and effectiveness, the Morris Water Maze has great utility in neurodegenerative research and is particularly important in understanding the progression of these diseases and the identification of potential treatments. With the increasing trend in cases of neurodegenerative diseases, the Morris Water Maze could not be more fundamental to gaining insights to help combat the devastating effects of neurodegenerative diseases on worldwide health.

Contact us today to find out more about how our cutting-edge research tools and solutions can be used to advance your neuroscience studies.

 References

1. Gitler, A.D., Dhillon, P. and Shorter, J. 2017. Neurodegenerative disease: models, mechanisms, and a new hope. Disease models & mechanisms. 10(5), pp.499-502.
2. Zahra, W., Rai, S.N., Birla, H., Singh, S.S., Dilnashin, H., Rathore, A.S. and Singh, S.P. 2020. The global economic impact of neurodegenerative diseases: Opportunities and challenges. Bioeconomy for sustainable development. Pp.333-345.
3. Durães, F., Pinto, M. and Sousa, E. 2018. Old drugs as new treatments for neurodegenerative diseases. Pharmaceuticals. 11(2), p.44.
4. Morris, R. 1984. Developments of a water-maze procedure for studying spatial learning in the rat. Journal of neuroscience methods. 11(1), pp.47-60.
5. Zhang, W. and Luo, P. 2020. Myocardial infarction predisposes neurodegenerative diseases. Journal of Alzheimer’s Disease. 74(2), pp.579-587.
6. Mulder, G.B. and Pritchett, K. 2003. The Morris water maze. Journal of the American Association for Laboratory Animal Science. 42(2), pp.49-50.
7. Lee, H.T., Lee, K.I., Chen, C.H. and Lee, T.S. 2019. Genetic deletion of soluble epoxide hydrolase delays the progression of Alzheimer’s disease. Journal of Neuroinflammation. 16, pp.1-12.
8. Zhang, D., Li, S., Hou, L., Jing, L., Ruan, Z., Peng, B., Zhang, X., Hong, J.S., Zhao, J. and Wang, Q. 2021. Microglial activation contributes to cognitive impairments in rotenone-induced mouse Parkinson’s disease model. Journal of neuroinflammation. 18, pp.1-16.
9. Bruszt, N., Bali, Z.K., Tadepalli, S.A., Nagy, L.V. and Hernádi, I. 2021. Potentiation of cognitive enhancer effects of Alzheimer’s disease medication memantine by alpha7 nicotinic acetylcholine receptor agonist PHA-543613 in the Morris water maze task. Psychopharmacology. 238(11), pp.3273-3281.

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Understanding the Morris Water Maze

The MWM is a large circular pool filled with opaque water, with a hidden escape platform submerged just below the surface. Rodents are placed in the pool and must use spatial strategies and local cues to find the hidden platform. The time taken to find the platform, known as escape latency, and the time spent in the quadrant where the platform was previously located during probe trials, are key measures of cognitive function and reference memory.

Tailoring the Experiment to the Mouse Strain

The background strain of the mouse model can significantly influence the observed behavioral phenotype. Some strains exhibit superior learning ability relative to others. Therefore, identifying a training procedure sensitive to the background strain is essential to detect differences between transgene-negative and transgene-positive mice.

Setting Up the Testing Environment

The testing room should be a quiet space with WiFi access and proper illumination. Spatial cues, such as different shapes cut out of colored paper, should be taped to the room’s walls. The maze should be set up several feet away from the experimenter’s seat to minimize distractions and interference.

Preparing the Water Maze

The tank should be filled so that the escape platform is one inch below the water’s surface. To make the water opaque, use non-fat dry milk or non-toxic white tempera paint. This ensures that the platform remains hidden, forcing the rodent to rely on spatial strategies and visual cues to locate it.

Conducting Training and Probe Trials

Rodents are initially given a series of learning trials, where they are allowed to swim in the tank until they find the hidden platform. Learning trials last a specific amount of time, but it is similarly important to specify the time between trials too. 

After the learning trials, a probe trial is conducted. The submerged platform is removed, and the time the animal spends swimming in the quadrant where the platform was previously located is measured. Rodents that have learned the platform’s location will spend most of their time in this quadrant, while poor learners will search other areas of the tank.

Considering Alternative Tests

If the MWM is not suitable for your research, consider alternative tests for spatial learning and memory, such as the radial arm maze or the Barnes circular platform maze.

By following these tips and tricks, researchers can optimize their Morris Water Maze experiments to better assess spatial learning and memory in rodent models. 

Looking Forward to Optimizing Your Spatial Learning Experiments?

At San Diego Instruments, we understand the complexities and nuances of conducting spatial learning experiments. Our expertise in this field has allowed us to develop tools that are tailored to the needs of researchers in this area, including our Morris Water Maze, which is ideal for testing rodent behavior and assessing spatial learning and memory.

Discover Our Morris Water Maze

Our Water Maze is available in both rat and mouse models, ensuring compatibility with your specific research needs. The maze is designed with seamless walls to eliminate inadvertent cues, enhancing the validity of your experiments. We offer clear platforms in both rectangular and round options, and they can be fixed or adjusted in height to suit your experimental design.

Furthermore, our Water Maze is compatible with our ANY-maze video tracking system, allowing for precise tracking and analysis of rodent behavior. We also provide an optional drain kit that fits any of SDI’s tanks, facilitating easy maintenance and cleaning of the maze.

Our Water Maze is constructed from durable, high-density polyethylene, ensuring its longevity and reliability in your lab. With a diameter of 48″ for the mouse model and 72″ for the rat model, our Water Maze provides ample space for your rodents to navigate and learn.

If you want to optimize your spatial learning experiments, we at San Diego Instruments are here to provide you with the tools and expertise you need. Our Morris Water Maze is just one example of how we can help enhance your research. For more information, please visit our product page.

References and further reading:

1. Weitzner DS, Engler-Chiurazzi EB, Kotilinek LA, Ashe KH, Reed MN. Morris Water Maze Test: Optimization for Mouse Strain and Testing Environment. J Vis Exp. 2015 Jun 22;(100):e52706. doi: 10.3791/52706. PMID: 26132096; PMCID: PMC4545046.
2. Nunez J. Morris Water Maze Experiment. J Vis Exp. 2008 Sep 24;(19):897. doi: 10.3791/897. PMID: 19066539; PMCID: PMC2872979.
3. Weitzner DS, Engler-Chiurazzi EB, Kotilinek LA, Ashe KH, Reed MN. Morris Water Maze Test: Optimization for Mouse Strain and Testing Environment. J Vis Exp. 2015 Jun 22;(100):e52706. doi: 10.3791/52706. PMID: 26132096; PMCID: PMC4545046.

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One of the behaviors often focused on is rotation activity, in which rodents continuously circle or turn around within a designated area, and both clockwise and counterclockwise turns are monitored. But why? Rodents may engage in rotation activity for several reasons, including drug treatments, environmental factors, and neurological conditions such as Alzheimer’s or Parkinson’s. Accurately monitoring and recording rotation activity is crucial to understanding how diseases impact the mind and body, which will support the development of suitable treatments. In this blog post, we look at how the rotation activity of unrestrained mice should be recorded to ensure accurate and reliable results.

What Equipment Do I Need for the Recording of Rotation Activity?

There are several instruments available for monitoring rotation activity in unrestrained mice, and the most suitable one for your application will depend on your research aim and experimental design. The most common options include a home cage wheel, an open-source voluntary running activity system, a voluntary wheel running system, and a rotometer. However, for the purpose of this blog, we will focus on how to record the rotation activity of unrestrained mice using a rotometer. 

A rotometer system typically includes testing stations (single or multiple), computer software, and a tracking system that all work together to monitor each turn a mouse makes and records the data in real time.

Accurately Recording Rotation Activity

With the right tracking system, the challenges of accurately recording rotation activity can be easily overcome. Depending on the application, common choices include a video-tracking system or a magnetic sensor attached or injected into the rodent model, and both record each turn the animal makes. However, as we explore in the following section, systems have different configurations, and animals can also be monitored by placing them in a harness without the need for implants or video monitoring.  The data is then recorded through computer software and saved until the researcher is ready to analyze it.

To ensure the rotation activity is not a result of an external force, it is important to consider the environment of the enclosure. This includes lighting, noise, and temperature, as these factors could impact the mouse’s behavior and lead to inaccurate data.

Where Can I Purchase Rotation Activity Instruments?

If you’re looking for a rotation activity for your research application, San Diego Instruments (SDI) offers a user-friendly, reliable Rotometer Activity System designed for use in Parkinson’s disease research and many other neuroscience studies. 

In terms of rotation activity, the Rotometer does not require implants or videos to accurately record this. This system uses an elastic harness and long leash, which is fixed outside the container, to enable accurate monitoring of clockwise and counterclockwise rotations. SDI’s Rotometer offers greater flexibility as up to 16 test stations can be run from one computer, and the compartment is designed to force the animal to turn within its own length. The key features of this instrument are the easy loading of test subjects, the option to measure full or half turns, real-time monitoring, and accurate reporting with our integrated software.

The software offers a high degree of accuracy by automatically recording session data and saving it into one file. It also enables researchers to pre-assign animals to a specific test station and set a pre-programmed protocol for each session. Each turn the mouse makes will be counted, including reverse, quarter, or full turns, and the risk of recording exploratory behavior is significantly reduced. As a result, you have a method of accurately recording the rotation activity of unrestrained mice to support a wide range of research applications.

Contact a member of San Diego Instruments today for a quote or additional information.

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What Are Conditioned Place Preference Systems?

Conditioned place preference systems are used to condition animals to associate a particular environment with the effects of a drug, resulting in a preference for that environment. The CPP  can be manufactured in different designs and apparatuses to suit specific research requirements. The use of floor textures, along with other contextual cues, helps establish the association between the drug and the environment. During the conditioning phase, animals spend more time in the drug-paired environment, indicating a preference for that specific environment. It is worth mentioning that some CCP systems are sound-attenuated to block out any external noise that could distract rodents, but not all systems are. 

Relapse in laboratory animals can be measured using drug-associated environmental cues. These cues trigger drug-seeking behaviors and provide valuable insights into the animals’ response to drug-related stimuli. By precisely measuring entries into chambers and utilizing a database system, researchers can capture every movement of the subject, facilitating accurate data analysis and interpretation.

Assessing Drug Temporal Profiles with a CPP

CPP is a valuable tool in behavioral science, pharmacology, and neuroscience research. It allows researchers to evaluate the rewarding properties of drugs and investigate the underlying mechanisms of drug addiction. 

For example, researchers have been able to study the rewarding properties of morphine by using CPP systems. The study was conducted by inducing rodents with morphine, placing them in a CPP, and monitoring the effects to measure the drug’s temporal profile and understand its affective properties. Additionally, CPP has been used to investigate the incubation of craving phenomenon in drugs like cocaine, shedding light on changes within the nucleus accumbens.

Benefits of CPP in Drug Studies

There are many advantages to using CPP in drug studies. It allows researchers to assess the temporal profile of drugs, which offers insights into the pattern of rewarding and aversive effects. Moreover, CPP helps evaluate the psychoactive properties of drugs in animals. The versatility of this system enables researchers to examine dose-dependent differences and explore the impact of drug administration timing and dosing.

Looking for Conditioned Place Preference Systems? 

San Diego Instrument’s Place Preference System is a powerful and easy-to-use system for monitoring an object or stimuli’s motivational impact on a testing animal. SDI’s Place Preference System uses a 4×16 photobeam array to log when an animal enters the chamber and how long it spends there. The system accurately records and reports standard activity data, including ambulation and fine movements and time-stamped (x,y) positions.

The unit offers an easy connection via USB, enabling researchers to run the system using laptops or computers. Additionally, the CPP stores all study results in a single file format, which removes the need to manage multiple files when exporting data.

The testing enclosure of the system features clear acrylic walls, providing the flexibility to attach any type of cue. The removable floors allow the creation of custom floors from various materials, catering to specific study requirements. The long-lasting, heat-free LED ceiling lights ensure optimal lighting conditions, while the manually operated doors offer clear pathways for subjects to cross between chambers.

If you require a conditioned place preference system, contact San Diego Instruments today, and we’ll be happy to help.

References and Further Reading

1. https://www.ncbi.nlm.nih.gov/books/NBK208615/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2756405/

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The Importance of Mice in Tremor Monitoring

Monitoring tremors in animal models enables researchers to obtain valuable information about the underlying mechanisms of conditions that result in tremors. For example, recent studies have shown that some genetic mutations in rodents result in tremors similar to those developed by human patients with Parkinson’s disease.1 Other reasons for using animal models in tremor monitoring include identifying new biomarkers for neurological disorders, and they are genetically similar to humans, making them ideal models for understanding more about neurological disorders.

Tremors as a Biomarker for Neurological Disorders

Monitoring tremors is critical for differentiating between types of tremors, their causes, and what treatment could be made available for them. As tremors can act as biomarkers for neurological disorders such as Parkinson’s disease, studies can monitor progression through behavioral changes in the mice, tremor events, and types of tremors, including any patterns.2

Methods of Monitoring Tremors in Mice

Several methods are available for monitoring tremors in mice and other small animal subjects, each of which has advantages and disadvantages. These include behavioral observation, electromyography, and motion sensors such as accelerometers.

Behavioral Observation

Behavioral observation is a non-invasive method that requires visual monitoring of a mouse for signs of tremors. This is a simple, cost-effective method, but its disadvantage is that it’s not sensitive enough to detect minor tremors and changes.

Electromyography (EMG)

EMG monitors the electrical activity of a mouse’s muscles during tremor events. This method is precise, but electrodes are inserted into the muscles, which may cause the animal pain or trauma. 

Accelerometers and other motion sensors

Sensors are a newer method of monitoring tremors in mice and are favorable due to their non-invasive nature. During the studies, sensors are attached to the mouse’s body, allowing body movement to be measured during tremor events. It is highly accurate, but specialist equipment is required.

By utilizing tremor monitoring systems, scientists can obtain a comprehensive understanding of tremor events and disorders in animal models by monitoring progress and using this information to understand the impact on human patients. 

Applications of Tremor Monitoring in Mice

We have covered some primary reasons for tremor monitoring, but we provide more detail in this section. Monitoring tremor events in mice can aid researchers in understanding the mechanisms of tremors and related neurological conditions. In turn, this can help develop new diagnostic tools and treatments for these conditions, offering patients a better quality of life. Tremor monitoring can also be used for drug discovery applications by monitoring the effectiveness of drugs designed to reduce tremor events.

San Diego Instruments

At San Diego Instruments, we specialize in providing high-quality behavioral neuroscience research instruments, including our tremor monitoring system. This system uses a highly sensitive movement sensor and is capable of differentiating between tremor events and ambulatory or stereotyped movements, thanks to its ability to record continuous movement waveforms at 128Hz for over 68 minutes. Users can also define short and long tremors to further refine their analysis, and up to eight testing stations can run from one computer.

Contact a member of San Diego Instruments today to learn more about tremor monitoring in mice and how our tremor monitor can support your applications.

References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3244549/
2. https://www.nature.com/articles/s41746-019-0171-4
3. https://www.sciencedirect.com/science/article/abs/pii/S0014299909005044

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Although humans and animals have the capacity for avoidance learning, moving forward, we will only discuss avoidance learning in mice. We will look at the differences between active and passive avoidance learning, their key features and why it is essential for research in this area to continue.  

Avoidance Learning

Avoidance learning is when voluntary behavior is learnt to prevent a negative stimulus before it occurs or avoid it altogether. These responses can only be developed after the avoidance response has been learnt, which requires a mouse to have experienced the aversive event previously. Many parts of avoidance learning are natural and essential for avoiding danger, but excessive or unnecessary avoidance behaviors can suggest anxiety disorders, thus making it an essential area of study in psychology. Avoidance learning and behaviors are commonly studied using mice in a laboratory setting.

Read more: The Basics of Avoidance Learning and Its Origins.

Active Avoidance Learning in Mice

Active avoidance learning occurs when a mouse learns to respond to an unpleasant stimulus in a specific way. In mice, the most common way to observe avoidance behaviors is by using a shuttle box apparatus, which includes two sections with a barrier between them. During the study, a light or noise stimulus is presented, followed by a non-harmful shock or stimulation of the paws. Over time, and through trial and error, the mouse must learn to move to the other compartment to escape from the unpleasant stimulus by recognizing the light or noise stimulus, also known as the conditioned stimulus.1 

The key features of active avoidance learning include presenting behaviors that would not occur without the negative stimulus. This is learnt through Pavlovian conditioning as the fear of an unconditioned stimulus forces the mouse to develop behaviors to avoid the unpleasant stimuli. The mouse model must also actively engage in the learning process that helps them escape exposure to the stimuli, which naturally would be part of their survival instinct in the wild.

It is, however, important to note that active avoidance learning and the fear response can vary between individuals, as some learn quickly and others do not. There are many reasons why some organisms do not engage in avoidance learning, including limited acquisition and retention of experience.1

Passive Avoidance Learning in Mice

Passive avoidance learning refers to behaviors that involve a mouse not engaging in certain behaviors to avoid an unpleasant experience.2 As the name suggests, passive avoidance training is a more passive process, unlike active avoidance learning, in which subjects must actively engage to avoid a stimulus. 

The method of studying passive avoidance learning is to use the step-through apparatus. Like the active avoidance chambers, a mouse will be placed in an apparatus with two compartments and a barrier in the middle. Firstly, into a brightly lit compartment and as they move into a dimly lit compartment, a paw stimulation, or shock, is activated.3 Over time, the mouse is trained to inhibit a natural response. Its avoidance learning is monitored by measuring its reluctance to enter the darker compartment, which would be a natural instinct.

Passive avoidance learning is simpler as it requires the mouse to do less. Although rodents naturally seek out darker environments, through this model, they will learn to avoid the darker compartment as they remember the shock administered.

Differences Between Active and Passive Avoidance Learning

Although we have mentioned some of the differences between active and passive avoidance learning theories throughout this blog post, we will summarize the key features of each learning style in this section.

Active Avoidance Learning

• Measured based on the occurrence of a specific response
• Requires active engagement from subject
• The subject learns to prevent an aversive stimulus

Passive Avoidance Learning

• Measured based on the non-occurrence of a response
• Passive engagement from subject
• The subject learns to avoid an environment where they have experienced an unpleasant situation

Both active and passive avoidance learning is studied to understand better how organisms respond to anxiety, fear, trauma and other disorders. In the field of psychology, studying active avoidance learning is crucial to learn more about the neural and behavioral mechanisms behind anxiety disorders and support the development of new treatments. Using mice models in these studies help researchers gain valuable information about these disorders and how they can be impacted by genetics and the environment.

San Diego Instruments

San Diego Instruments design and develop a range of life science instruments for behavioral neuroscience research. The GEMINI active and passive avoidance system is designed to accurately and reliably monitor learning and memory in rodent subjects for avoidance learning. 

The GEMINI allows up to 8 independent avoidance chambers and provides cues such as non-heating LED house lights, standard cue lights, and various auditory stimuli. For unconditioned stimulus, it offers an air puff or shock option.

Contact a member of San Diego Instruments today to learn more about active and passive avoidance learning and the apparatus we provide for enhancing your studies.

References

1. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/active-avoidance-test
2. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/passive-avoidance
3. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/step-through-passive-avoidance-test

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Experimental setup

Scientists need several apparatus and equipment to accurately and efficiently monitor acoustic startle response in mice. One of the challenges with quantifying acoustic startle response is that it happens extremely quickly, giving researchers little time to capture the response. With this setup, the mice used as test subjects can be monitored closely for safety reasons and to ensure the experiment results are accurate.

Startle Chamber

The mouse is placed inside a restraint inside a startle chamber, so it is in a confined and safe space. Startle chambers are fitted with speakers, as a loud noise is used as a stimulus, and a transducer to measure the response.

Acclimation period

Before any tests occur, the mouse is given a short period to acclimate and become familiar with the startle chamber. Allowing an acclimation period reduces the chance of inaccurate results, as mice should only respond to the stimuli, not parts of the chamber.

Presentation of Acoustic Stimuli

Once the acclimation period is over, a set of acoustic stimuli are triggered over various intervals. Gradually, the sound intensity is increased so researchers can gauge the point that initiates a startle response. 

Measurement of Startle Response and Pre-Pulse Inhibition

During this stage, researchers might measure the pre-pulse inhibition (PPI) of the startle response, another feature crucial for understanding the CNS. PPI often happens in response to a quieter sound before the startle-inducing noise and can often reduce the intensity of the startle response. A startle response can be exhibited through rapid contraction of facial and skeletal muscles, which can look like an entire body flinch, the extension of forepaws and hind paws followed by a hunched position, and a change in facial expression or eyeblinks.

Once these steps have been taken, researchers can analyze the data collected from the experiment.

Analysis of Data

Analyzing the data from startle response experiments typically requires specialized software. The software will generate reports based on the startle response and prepulse inhibition (PPI) data for each mouse or each testing group. Once the data has been analyzed and presented, researchers can use this information to compare results between different mice or testing groups. This is often conducted when one group has a genetic modification or is treated with specific drugs and compared with a different group.

Quantifying Acoustic Startle Response with San Diego Instruments

San Diego Instruments offers a range of products that can be used to monitor and measure acoustic startle response in mice. Our SR-LAB acoustic startle response system is widely used to quantify acoustic startle response, PPI, and fear-potentiated startle (FPS) in research settings. 

The SR-LAB system is a comprehensive hardware and software solution that can be used with various startle response applications, with the option to add up to 16 stations for high throughput experiments. The SR-LAB software offers control of multiple stimuli such as air puffs, lights, noise bursts, foot shocks, and background noise, and various test paradigms can be initiated without the need for extra software.

Contact a member of SDI today to learn more about quantifying acoustic startle response.

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