Effects of chemicals on delayed matching in pigeons IV: Effects of trimethyltin.

The effects of trimethyltin on delayed matching to sample performance of male White Carneaux pigeons were studied using the delayed matching-to-sample and the reversed delayed matching-to-sample procedures. In the delayed matching-to-sample procedure, pigeons were trained to peck a red or green center key 15 times to turn it off. After a 2- or 5-sec delay, one side key was illuminated by a red color and the other by a green color. One peck on the side key whose color was the same as the center key had been, produced food. After performance had stabilized, trimethyltin was administered intramuscularly at 3 different dosages (1.0, 1.3, and 1.75 mg/kg) to 3 different groups of birds. Birds received 3 injections of the same dose with injections at least 14 days apart. Trimethyltin produced dose-dependent decreases in matching accuracy, with smaller effects on response rate. Delay duration-dependent decreases in matching accuracy were also observed, whereas effects on response rate were independent of delay duration. These behavioral effects disappeared with time in all but one animal, who was unable to perform even 89 days after trimethyltin. There was no evidence of cumulative effects of trimethyltin in the other animals. After completion of the experiments with the delayed matching-to-sample procedure, pecking the key different in color from the sample key was required for reinforcement (reversed delayed matching-to-sample). There were no differences between trimethyltin-treated birds and non-treated controls in acquiring the reversal performance.