ABA chronic dosing of D-amphetamine produces differential drug effects in two variants of a temporal discrimination procedure in pigeons

The impact of two procedural variants of the matching to sample of duration procedure on the effects of chronically administered D-amphetamine on temporal discrimination was assessed. The task consisted of subjects classifying durations as short or long to produce a psychophysical curve for time. Procedural variations included response alternatives being defined by either the location of the response keys (Location), or by their color (Color). During Phase 1, two groups of pigeons experienced one of these procedures while being administered with D-amphetamine in an ABA chronic dosing regimen. Phase 2 was a reversal condition in which select birds from Phase 1 were trained on the other procedural variation that they had not experienced and were again given D-amphetamine in an ABA chronic regimen. Results showed that during Phase 1, subjects in the Color group showed a flattening of the psychophysical curves during amphetamine administration, whereas those in the Location group showed a shift of the psychophysical curve to the left and right. Phase 2 revealed that subjects who had experienced the Location variant first were less disrupted by the drug, even when experiencing the Color condition. The procedural variation, dosing regimen, and form of data analysis all provide more information regarding the cause of discrepancies in the timing literature regarding differential effects of D-amphetamine on timing behavior.