Measuring the actual timing of liquid-reward delivery using a thermistor.
BACKGROUND
Determining the exact timing of reward delivery is critical in neurophysiological experiments. Despite the importance of this parameter, techniques for precisely measuring the exact delivery time of a liquid reward have been underdeveloped. Although there is always some latency between the computer command and reward delivery, the former has been used routinely to mark reward onset time.


METHODS
To address this issue, we developed two methods of estimating the time of liquid reward delivery. First, electrical conduction between two contacts at the outlet of a pipe was detected. This technique was impractical during normal experiments but was a direct and reliable method of measuring the precise timing of water outflow. Second, a self-heating thermistor inside the fluid delivery pipe was used. The thermistor detected a decrease in temperature upon commencement of water flow.


RESULTS
The electrical contact began 50-80ms after the computer command. The thermistor-based delivery timing estimation was ∼40ms later than that measured by the electrical contact. The time lag was constant with minimal variance between trials within the same experimental setup.


CONCLUSIONS
As far as the time difference between the two methods is measured, the timing of water outflow can be estimated using the thermistor-based device. This is the first method of estimating the onset time of water flow during experiments.


CONCLUSIONS
Our new system could be used to quantify setup-dependent changes in the timing of reward delivery, improving the sophistication of reward assessments in neurophysiological experiments.
Systems Neuroscience, Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan; Department of Neurobiology, Duke University School of Medicine, Durham, NC 27701, USA; Japan Society for the Promotion of Science, Tokyo 102-0083, Japan.
Koji
K
Toda
Systems Neuroscience, Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan. Electronic address: yamane-shigeru@aist.go.jp.
Shigeru
S
Yamane
Systems Neuroscience, Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan. Electronic address: yamamoto-s@aist.go.jp.
Shinya
S
Yamamoto
D000818:Animals; D004553:Electric Conductivity; D055615:Electrical Equipment and Supplies; D004867:Equipment Design; D009482:Neurophysiology / Q000295:instrumentation* / Q000379:methods*; D012201:Reward; D013696:Temperature; D013995:Time; D014867:Water / Q000008:administration & dosage*
D014867:Water
Electrical contact; Liquid reward; Neurophysiology; Thermistor; Timing estimation