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UCSD MED Measure Cerebellar Dependent Learning

Introduction to Research Motivations:

The mouse cerebellum represents an ideal system for studying neuronal development and gene regulation in the brain during learning. This is because the circuitry of the cerebellum is relatively simple, consisting of just two major neuronal sub-types: Purkinje cells and Granule cells(see below). However, a major limitation of studying the cerebellum is the lack of behavioral tests that specifically require cerebellar-dependent associative learning. One exception is the underutilized Pavlovian paradigm of delayed eyeblink conditioning. In this test, mice learn to blink in response to a neutral conditioned stimulus (CS, usually a blue light) when it is repeatedly paired with an aversive, eyeblink−eliciting periocular airpuff (the unconditioned stimulus or US). When the CS and US are rapidly paired, typically with an interstimulus interval of 100-400 ms, motor learning requires the cerebellum. No similar device exists on the UCSD campus, and therefore this project represents an opportunity to add an important tool for use by our institution’s world-class community of neuroscientists.

Taken from MAE156a Project Description

Introduction to Project Background:

Our sponsor, Dr. Cole J. Ferguson, who works as a neuroscience researcher for UCSD Health, has been investigating Cerebellar-dependent motor learning in mice. This research uses a unique custom made apparatus to condition the mice and record their behavior. The mouse being trained first undergoes a surgical operation during which a metal plate is attached to its skull. Those metal plates are then screwed onto the rig above a treadmill meant to give it the possibility to freely run and therefore reduce its stress. Once the mouse has its head fixed and static two different stimuli are presented to it. An LED light first turns on in front of it and shortly after a blink-inducing puff of air is directed at one of its eyes. An infrared light and a high-speed camera are also pointed at the mouse’s eye in order to precisely record the timing of its blinks. After repeated exposure to the light followed by the puff of air it can be observed that the mice blink as soon as they see the LED light turning on, therefore anticipating the puff of air. Conducting this kind of eyeblink conditioning has been shown to be very effective at assessing the good functioning of the cerebellum and the neural mechanisms underlying motor learning in mice. By testing genetically modified mice with known defects in the cerebellum our sponsor will be able to map which mutations are responsible for improved or altered learning capabilities. Our sponsor started his research with such an apparatus at his previous lab in 2014 but unfortunately he could not bring the rig over to UCSD with him, he therefore tasked us to rebuild it and improve it in order to continue his studies here.

Project Objective:

In 2014, the project sponsor Dr. Cole Ferguson worked with a team to develop and test the first version of an apparatus that served to track cerebellum dependent learning in mice. The objective of this project was to create an improved version of the 2014 apparatus to test cerebellar-dependent associative learning in mice. A successful apparatus is validated through continuous observed learning in mice that are subjected to paired conditional stimulus (light) with unconditioned stimulus (air puff). For learning to occur, the rig must meet certain primary requirements. The first primary requirement was that the head-fixed mice must be able to run freely on the wheel during testing, as mice comfort throughout testing had been shown to be crucial to enable the collection of data relevant to learning. The next requirement was the usage of a blue LED to act as the conditioned stimulus. Additionally a needle was to be placed in proximity to the mouse's cornea to administer an air puff, serving as the unconditioned stimulus. Eye blinking was to be tracked and timed following mice exposure to stimuli. Lastly, the system required a sensory attenuating enclosure to shield the system from the surrounding environment in order to ensure undisturbed experimental results. Overall the apparatus was intended to be used continuously over a long period of time so durability and reliability were essential.

Final Design:

The final design of the cerebellar dependent learning apparatus uses MATLAB image processing software coupled with a teensy microprocessor to automate the stimulus delivery and record the resulting data. The mouse is secured onto the wheel with custom made head mounting plates and arms, while the LED and air puff needle are secured to precision arms and directed at its eye. A high speed camera illuminated by an infrared light is positioned to capture eye blinking. The system is enclosed by a sound-attenuating box, assisted by a white noise generator, to maximize sensory attenuation.

Performance Results:

Overall, our team was successful in meeting the sponsor’s goal of creating an improved version of the 2014 Cerebellar Dependent Learning apparatus. A major improvement to the apparatus was eliminating the software crashes present in the previous version, via the switch from GigE to USB 3 data collection and streaming. Additionally, the axle of the wheel component was simplfied in order to limit the need for custom manufactured components, along with the use of shielded bearings to ensure long-term functionality. The sound attenuating box was picked not only based on its sensory attenuating abilities, but also for its significantly increased size in comparison to the box utilized in the 2014 experiments. This was done in order to increase the accessibility to the wheel for mouse attachment between tests. Through the implementation of these considerations, the system’s reliability and durability were substantially improved. The apparatus was delivered over two weeks early to Dr. Ferguson's lab, allowing for preliminary testing and results from new experimentations. Furthermore, the project was successfully completed under budget. The sponsor was extremely pleased with the finished rig and current results. Dr. Ferguson currently plans to include our team as co-authors on the first paper published using the new 2021 rig.

Final Presentation Zoom Link 3/17/21:

https://ucsd.zoom.us/rec/share/Nurk0Qd8OKy_kGXF6xfqxLiabErimcCijN8JAvrweoHOy_-w0CR2K-JhkZEcMUNp.tRkpOJLV8FFO7iUr?startTime=1616005556000