Sign-Tracking and the Integrated Reward System

Sign-tracking video 2: Alcohol sipper paired with food.
This video shows procedures similar to those of video 1, except that the retractable lever has been replaced by a retractable alcohol sipper tube. In video 2, the insertion of the alcohol sipper tube precedes the delivery of the food pellet. The food pellet is delivered regardless of what the subject does. The alcohol sipper tube, located to the right of the food tray, is inserted for 5 sec just before the presentation of the food reward. Pairings of the alcohol sipper with the food reward induces Sign-Tracking. The Sign-Tracking rat approaches the alcohol sipper, contacts the alcohol sipper, then licks and “consumes” the alcohol sipper. Note that the performance of the Sign-Tracking response results in the drinking of the alcohol inside the sipper, which flows into the mouth of the rat each time the rat contacts the end of the sipper tube. Sign-Tracking of alcohol drinking is a form of alcohol drinking that is induced by mere pairings of the alcohol sipper with food.

The subject in this video is a Long-Evans hooded rat. This strain of rat typically drinks little or no alcohol. But, during a one-hour session of training with Sign-Tracking procedures, the Long-Evans hooded rat drinks more alcohol than during a 24-hour period with continuous access to alcohol in the home cage. This suggests that the amount of alcohol drinking that is induced by this Sign-Tracking procedure is far in excess of that intended.