A novel method for detecting licking behavior during recording of electrophysiological signals from the brain

We have developed a novel method for detecting licking at a fluid well that is compatible with behavioral neurophysiology. This method uses off-the-sh elf fiber optic technology to introduce a light beam through the fluid-air interface of a fluid bolus in a well. A self-adjusting optical sensor detec ts licking as disturbances in the amplified light surface within the interf ace when the fluid is disturbed. The proper configuration of fluid well and fiber optics will reliably detect licking and introduce no artifacts into simultaneous high-impedance recordings of extracellular neural activity. Th is method is also compatible with delivery of multiple fluids to the same w ell. Unlike present methods of detecting licking in neurophysiological expe riments, our approach does not involve the passage of current or capacitanc e changes in which the animal forms part of a circuit, nor does it require movement of the licking apparatus or any other response beyond the actual l icking of the fluid. As a result, noise artifacts in the unit recordings do not occur, and the sensor is highly resistant to artifacts caused by explo ration or licking at the fluid well in the absence of liquid. We present ne ural recording data from units in the nucleus accumbens demonstrating these properties of the lick detector. (C) 2001 Elsevier Science B.V. All rights reserved.