Final Design

Design Overview:

The largest component of this apparatus is the wheel system. Its purpose is to support the head fixed mice undergoing experimentation, while allowing them to walk or run comfortably in place. The wheel is held in place by aluminum support rods, and rotates freely on an aluminum axle with nested bearings. The mice head fixture is attached to the top of the aluminum support rods holding the wheel. The mice head fixture, which is surgically attached to the mice skulls, ensures that the mice cannot move their heads during experimentation. A neighboring aluminum rod holds a blue LED light, a needle controlled by an air injector designed for air puff delivery to the mouse cornea, and a camera designed to accurately and consistently capture the degree of mouse eye closure. These three components are positioned to face the mouse head on, to ensure both prompt delivery of stimuli, and accurate tracking of mice response during experimentation. They are automated using a Teensy microprocessor and processed using MATLAB imaging software.

Eyeblink System:

The eyeblink system consists of the LED light, air delivery needle, air compressor, and MPPI-3 pressure regulator. It provides the stimulus in the form of a blue LED light flash followed by a 20-30 ms air puff to the mouse's cornea. The air tank provides the necessary pressure for over 1000 puffs of air per full tank, which is sufficient for a day of experimentation.

Summary of Design Purpose and Results:

The mouse cerebellum is a suitable biological neural network for drawing parallels to cerebellum dependent learning in humans. One way of studying the mouse cerebellum involves the Pavlovian paradigm of delayed eyeblink conditioning. In order to provide an environment for learning to occur, a neutral conditioned stimulus is paired repeatedly with an unconditioned stimulus. This experimental process is meant to elicit motor learning which in turn demonstrates successful use of the cerebellum. In this experiment the neutral conditioned stimulus is the flashing of a blue LED light, and it is immediately paired with the unconditioned stimulus, which is a periocular puff of air of approximately 100-400 ms. These stimuli are repeatedly delivered to the subject mices’ eyes in effort to demonstrate cerebellar-dependent learning over time. For this project, the team was tasked by the sponsor Dr. Ferguson, to recreate and improve an apparatus created in 2014 which tested cerebellar dependent associative learning in mice using the described paradigm above. The major components of this apparatus are a high speed camera system to capture mice eye blinks, a flashing blue LED to serve as the conditioned stimulus, an air pressure injector system to administer the unconditioned stimulus, and a free spinning wheel to comfortably support the subject mice during experimentation.

Ultimately, the team was successful in meeting the sponsor’s goal of creating an improved version of the previous Cerebellar Dependent Learning apparatus. A major improvement to the apparatus was eliminating the software crashes present in the previous version, through the switch from GigE to USB 3 data collection and streaming. Additionally, the axle of the wheel component was modified in order to limit the need for custom manufactured components. The sound attenuating box was picked not only based on its sensory attenuating abilities, but also for its increased size in comparison to the box utilized in the 2014 experiments. This was done in order to increase the accessibility to the components inside in case of necessary or desired modifications to the configuration. Through the implementation of these considerations, the system’s reliability and durability substantially improved. The apparatus was delivered two weeks early to the sponsor to allow for preliminary testing and possible results from actual mice experiments. Furthermore, the project was successfully finalized under budget. The sponsor was extremely pleased with the finished rig and plans to include the team as co-authors on the first paper published using the rig.