A user-friendly graphical user interface for paw touch classification in rodent cylinder testing

In unilateral rodent models of disease or injury, deficits are induced in only one side of the body, allowing the difference in right versus left limb usage to serve as a metric of disease/injury severity and recovery with various treatments. Unilateral rat models are commonly used for conditions such as Parkinson's disease (via the neurotoxin 6-hydroxydopamine, 6-OHDA), stroke, and traumatic brain injury, as well as cervical spinal cord injury and peripheral nerve damage. The 'cylinder test' has been used for over two decades as a reliable metric of asymmetry in forelimb usage. In this test, videos are taken of the rodent in a vertical cylinder as it explores its surroundings. The experimenter then logs which forepaw was used to first touch the cylinder wall each time the animal reared up on its hind limbs to start a new wall exploration sequence. The process of manually scanning through videos and logging left/right paw touches can be very time consuming and prone to errors. To streamline this process, we made The Ratalyzer, an easy-to-use graphical user interface (GUI) that: (1) facilitates efficiently moving through videos to find each initial wall touch event, (2) blinds the assessor to the animal and treatment state, and (3) electronically logs the paw-touch event type and time with just a push of a button thus eliminating error-prone paper notes or manual data entry. We are making this useful software tool available to the research community as both a compiled stand-alone program and as open-source MATLAB code. This tool could be useful for both researchers and educators, as analyzing cylinder-test videos via this GUI is a great way to engage high school and undergraduate students in performing neuroscience research without the risks and costs associated with making live animals available to students for hands-on testing.