My friend MIROSLAV: A hackable open-source hardware and software platform for high-throughput monitoring of rodent activity in the home cage.

While conventional behavioural tests offer valuable insight into rodent behaviour in specific paradigms, rodents spend most of their time in a safe, undisturbed environment-their home cage. However, home cage monitoring (HCM) is often impractical at scale over prolonged periods of time without significant loss of data. To achieve this, we developed MIROSLAV, the Multicage InfraRed Open-Source Locomotor Activity eValuator, a home cage activity and environmental monitoring device designed to be open, adaptable, and robust. Its transparent and modular design allows the device to be tailored to varying experimental requirements and environmental conditions, while its wireless operation and multiple redundancies minimise loss of data and animal disturbance. Data quality is maintained by a modular software workflow for data preparation (Prepare-a-SLAV) and cleaning (TidySLAV), followed by exploratory (MIROSine-MIRO The Explorer) and statistical (MIROSine-StatistiSLAV) analysis of circadian periodicity. Here, using MIROSLAV, we demonstrate circadian dysrhythmia and a disrupted response to regular stimuli (e.g. behavioural testing, bedding change) in a rat model of sporadic Alzheimer's disease, showcasing MIROSLAV's utility in a typical animal study of disease. In accordance with the 3Rs (replacement, reduction, and refinement), every rodent study and laboratory performing them can benefit from HCM, provided the existence of transparent and customisable tools which allow robust deployment to tens or hundreds of cages in various conditions. MIROSLAV provides this opportunity to researchers in a cost-effective manner.