A novel rodent accelerometer device for measuring locomotor activity and other movements

Abstract

Locomotor activity is a simple, yet useful measure of drug-induced changes in rodent behavior. Current methods for assessing activity often fail to capture more complex behavioral topographies, such as stereotypy, require measuring movement in novel environments, and/or require invasive surgeries. Here, we describe a novel device that wirelessly transmits fine motor behaviors at high frequencies. An accelerometer (Biosense, Palo Alto, CA) encased in a plastic covering (2 cm × 1 cm × 0.5 cm) is adhered to the skin between the scapula of a rodent. The device records changes in acceleration (m/s2) and converts it to frequency (Hz) using a Fourier transform. Data is collected about 50,000 times per 10 minutes and is sent to a computer via WiFi. Once new data is uploaded to the cloud (Google Cloud), a system processes the raw accelerometer values and quantifies certain types of activity using proprietary Python code. The processed data is accessible via an online web portal. To compare this novel approach with established methods, male Sprague Dawley rats were habituated to a novel acrylic cage (14” × 14” × 8”) for 90 minutes then were treated with amphetamine (0, 0.32, 1.0, 3.2 mg/kg subcutaneous, n=8 per dose). Locomotor activity was recorded using infrared beam breaks (Columbus Instruments, Columbus, OH) and the accelerometers simultaneously in the same rats. Amphetamine dose-dependently increased locomotor activity in both measures for approximately 2.5 hours, with the magnitude and duration of the effect being closely correlated between the two measures. Further, only the accelerometers were able to identify and quantify stereotyped movements and other behaviors, such as walking, running, or wet-dog shakes. In addition to locomotor activity, the devices were able to detect pentylenetetrazole-induced convulsion related movements (56 mg/kg subcutaneous, n=6) and increased activity during the dark cycle as compared with light cycle in the home cage (n=8). This novel method for recording rodent activity will be a useful approach for capturing and quantifying complex drug-induced behaviors as well as changes in circadian behavior in known and novel environments.