Monitoring Lick Responses in Animal Behavioral Experiments Using a PSoC

Research on hearing often involves quantitative measures of behavioral responses to the way that sound is perceived. Experimental measures of auditory perception, in animals in particular, need robust methods for monitoring behavioral responses such as licking a water spout for a reward, or body position. Recent advances in embedded systems have provided a flexible, low-cost and reconfigurable technology: programmable system-on-chip (PSoC) which integrates a microcontroller, programmable analogue functions and programmable digital peripheral functions in a single chip. This makes it appropriate technology to be embedded in computer controlled experimental equipment. A PSoC setup was designed for monitoring behavioral responses during experiments studying how ferrets perceive sound. The monitoring system consists of 13 ´lickometers´ which measure responses at water spouts, a beam breaker to monitor body position, a PSoC board and a PC USB interface. It is manipulated by custom firmware and driver. The firmware instructs the PSoC hardware to measure the signals when spouts are licked and to signal licking events and beam break events. The driver allows communication between the application program and the firmware. A novel and practical methodology is adopted for online lick signal processing, making use of PSoC´s digital threshold-crossing detection, analogue measurements and interrupt responses. Based on the online signal processing methodology, an algorithm is developed for categorizing lickometers´ states into 4 categories: Licked, Water drop residue, Vibrating water drop residue or End Event.