Effects of acute and daily cocaine administration on performance under a delayed-matching-to-sample procedure

Food deprived pigeons were trained under a procedure in which trials began with the transillumination of one of three keys by red or green light. Pecking this key extinguished the light behind it and, after a variable delay (0.05, 0.5, 1.0, 2.0, or 4.0 sec), was followed by illumination of the two other keys, one by red light and one by green. Pecks on the key that was the same color as the previously illuminated key could produce access to food. High levels of accuracy were obtained at all delays. The acute and chronic effects of cocaine on performance generated by this procedure (delayed-matching-to-sample) were studied. Acutely, cocaine (0.56-10.0 mg/kg) produced dose-related decreases in accuracy and in rate of completing trials. Accuracy at the longest delay was more sensitive to cocaine's effects. Daily administration of a comparatively large dose (5.6 mg/kg) resulted in tolerance to the rate-reducing and accuracy-reducing effects of large doses.