A low-cost, reliable, high-throughput system for rodent behavioral phenotyping in a home cage environment

Abstract

Inexpensive, high-throughput, low maintenance systems for precise temporal and spatial measurement of mouse home cage behavior (including movement, feeding, and drinking) are required to evaluate products from large scale pharmaceutical design and genetic lesion programs. These measurements are also required to interpret results from more focused behavioral assays. We describe the design and validation of a highly-scalable, reliable mouse home cage behavioral monitoring system modeled on a previously described, one-of-a-kind system. Mouse position was determined by solving static equilibrium equations describing the force and torques acting on the system strain gauges; feeding events were detected by a photobeam across the food hopper, and drinking events were detected by a capacitive lick sensor. Validation studies show excellent agreement between mouse position and drinking events measured by the system compared with video-based observation--a gold standard in neuroscience.

Fig. 1

The system consists of a powder-coated black aluminum base with three indended tracks, allowing any combination of three modules to be used at a time. In the configuration pictured, the feeder module is loaded in the first slot, a blank plate covers the second slot, and the liquid dispenser is installed in the third slot. The control board for the adjacent cage is also visible to the right.

Fig. 2

Validation of strain gauge localization. Top row: mouse movements tracked with EthoVision. Object in cage upper left hand corner is a cartoon of mouse niche showing entrance; in reality, the entire square niche was opaque when observed from above. Object at cage lower left corner is a cartoon of the feeder; object at cage lower right corner is a cartoon of the sipper tube. Bottom row: mouse movements tracked by the HCM.

Fig. 3

Series of licks simultaneously observed by HCM and high-speed videography. Open circles depict HCM determination of when the tongue begins (green) and ends (red) contact with the sipper tube. Plus signs depict observer determination (from high speed video frames) of when tongue begins (observer 1 cyan, observer 2 magenta) and ends (observer 1 blue, observer 2 black) contact with the sipper tube. Note HCM determined that the second manually scored event was actually a missed lick. X axis time in ms since data acquisition started; Y axis lickometer voltage. Below, an exploded detail of a single lick event. Lowercase letters along lick trace correspond to frames at right. Note that for frames (a) and (b) that the tongue is protruding from the mouse’s mouth but has not contacted the sipper tube; frames (c), (d), and (e) the tongue is in contact with the sipper tube, and frame (f) the tongue has been retracted back into the mouth.