Unlocking New Insights in Rodent Reward Systems: Virtual Reality vs. Traditional Methods

Virtual reality (VR) has emerged as a transformative technology with far-reaching applications across multiple fields, including healthcare, education, entertainment, learning and development and architecture amongst others.

In neuroscience research, VR has become a valuable tool for studying brain and behavioural processes, particularly in animal models such as rodents, by creating controlled environments where researchers can observe reactions to various stimuli. This adaptability and versatility have positioned VR as a powerful tool, revolutionizing the way we interact with and understand the world around us.

Let’s look at the key benefits of VR-based equipment over traditional systems like mazes and operant chambers, particularly when studying the intricate mechanisms of reward anticipation, processing, decision-making, effort-based choice and motivation in rodents.

1. Enhanced Experimental Flexibility

The traditional mazes and operant chambers generally offer less flexibility. The animal's movement is confined to a pre-determined path, and reward delivery is typically based on reaching a specific location in a maze. On the other hand, operant chambers are usually limited to straightforward tasks like lever pressing or nose poking, unable to offer variation in task complexity. Changing reward parameters or environmental cues often requires physical modifications or manual intervention, which is cumbersome and less adaptable, specially during an ongoing study. One of the most significant advantages of VR based equipment over traditional mazes and operant chambers is the flexibility it offers to experimental design. Highly customizable VR environments allow researchers to create complex, dynamic tasks, deploying multiple aspects of the reward system with ease. Researchers can change task parameters in real time, allowing for greater exploration of the reward system and how animals learn to maximize rewards under varying conditions.

2. Precision in Reward Delivery and Task Control

Reward delivery in traditional mazes and operant chambers can be less consistent and precise. In operant chambers, rewards are dispensed manually or with semi-automated dispensers that may introduce slight delays or variations in timing. Modifying reward parameters mid-experiment can be inconvenient and can introduce unwanted variability, complicating data interpretation. In virtual reality, reward delivery can be extremely precise and consistent. This level of control allows researchers to examine how rodents evaluate different types of rewards, adjust their expectations, and monitor their decision-making process in response to a variety of reinforcement models.

3. Ability to Simulate Complex Reward-Based Decision-Making

While traditional mazes and operant chambers are effective for studying basic reward-seeking behaviours, they are often limited in their ability to simulate complex decision-making tasks. In mazes, rodents navigate simple paths to obtain rewards, while in operant chambers, animals perform straightforward actions (e.g., pressing a lever) to receive reinforcement. VR systems allow for the design of highly complex reward-based decision-making tasks. In a virtual environment, researchers can simulate scenarios where rodents must decide between multiple rewards that vary in terms of effort, time delay, or probability. Another decisive advantage is the repetitiveness of the task, i.e., the animal is teleported back to the start after the first attempt. It is therefore possible to modify the task without having to change the hardware. This makes VR systems ideal for studying advanced cognitive functions.

4. Real-Time Data Collection and Behavioural Monitoring

Traditional mazes and operant chambers rely on more basic behavioural measurements such as latency to reach the reward or frequency or number of responses against a reward. Although video tracking and automated recording systems can be added to measure more complex behaviours, they often lack the resolution and integration that VR systems offer. VR offers a dynamic and customizable space for more sophisticated behavioural assessment. It allows for detailed monitoring of the animal's movements, trajectory, and interaction with the virtual environment in real-time. It can capture multiple parameters such as the time spent in different regions of the virtual space, the speed and direction of movement, and specific behaviours associated with reward-seeking action, to provide a richer dataset. You can also easily introduce randomness and variability into the test design.

5. Reduced Physical and Stress-Related Variables

VR systems reduce the physical and environmental stressors that are common in traditional setups. Animals can engage with the virtual environment without the need for strenuous physical activity or extended confinement. This isolation of reward-related behaviour from stress-induced effects helps researchers better study reward processing.

6. Ability to Integrate with Neural Recordings

While operant chambers and mazes can also be used in combination with neural recording techniques, the integration is often less seamless compared to VR, and requires physical adaptations/changes (e.g., implants, electrode wires) that can restrict the animal’s movement or alter its natural behaviour. In contrast, VR systems provide more flexibility in accommodating neural recording equipment while allowing the rodent to move freely within an immersive virtual environment. The ability of VR systems to be seamlessly integrated with advanced neural recording technologies like in-vivo, electrophysiological and optogenetic allows researchers to track how specific neural circuits or brain regions involved in reward processing respond to varying reward conditions in real time.

7. Elimination of Experimenter Bias

In traditional setups, experimenters may unknowingly provide subtle cues through their actions, such as adjusting the reward schedule or positioning themselves near the animal. These cues can lead to unintended behaviours that may negatively impact the results of the study. VR systems eliminate this potential source of bias by providing an entirely controlled, automated task environment. In a virtual environment, the animal interacts exclusively with the virtual world, ensuring that the behavioural data reflect the animal's response to the experimental variables, rather than experimenter’s influence.

8. Reduced Habituation in long-term studies

In long-term studies using traditional setups, animals can become overly familiar with the task and environment over time, which can reduce their motivation to perform a task. This can make it harder to track changes in behaviour over long periods. VR systems are great for long-term studies as they provide an environment that can be easily modified to keep the animals engaged, thereby preventing the animals from getting bored or overly familiar with the task. Introducing randomness into the test design prevents habituation and ensures that the animals remain motivated throughout the study.

Conclusion

Virtual reality-based equipment offers numerous advantages over traditional mazes and operant chambers for studying the reward system in rodents. The key benefits include enhanced experimental flexibility, precise control of reward parameters, the ability to simulate complex reward-based decision-making, and real-time behavioural monitoring. VR systems also provide a controlled environment that reduces physical stress, eliminates experimenter bias, and integrates seamlessly with neural recording technologies. These advantages make VR a powerful tool for advancing our understanding of reward processing, motivation, and decision-making in rodents.

At Phenosys, we spent years developing and refining our virtual reality systems for animal behaviour research. This has been done in close collaboration with world-leading neuroscientists. The Jetball spherical treadmill, available with TFT surround monitor or dome (a spherical 1.2 m igloo type screen), and the double-disk treadmill are popular products in our VR line-up. For more information on our offerings, visit: https://www.phenosys.com/products/virtual-reality/

As a leading VR systems provider for animal research, we are proud to partner with the BrainVisionCenter to bring you their revolutionary innovation- Moculus. Moculus is an immersive, head-mounted virtual reality headset for mice. It will open up new possibilities for studying the brain and improving brain-computer interfaces to restore vision https://www.nature.com/articles/s41592-024-02554-6

For more information or to get a quote, write to us at [email protected].

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