Schedule-dependent effect of d-amphetamine on pausing by pigeons

Area of Science:

• Behavioral pharmacology
• Animal behavior
• Operant conditioning

Background:

• Stimulant drugs like d-amphetamine are known to alter behavior under various reinforcement schedules.
• Understanding schedule-dependent effects is crucial for predicting drug impacts on complex behaviors.

Purpose of the Study:

• To investigate the effects of d-amphetamine on pigeon key-pecking under a multiple fixed ratio/fixed interval schedule.
• To determine if d-amphetamine's effects are dependent on the specific reinforcement schedule or overall response rate.

Main Methods:

• Pigeons were trained on a multiple schedule: fixed ratio (FR) with one stimulus, fixed interval (FI) with another.
• The FI schedule's parameters were adjusted to match the average rate of reinforcement in the FR component.
• d-Amphetamine was administered, and its effects on response rates and pausing were analyzed for each component.

Main Results:

• d-Amphetamine decreased overall response rates in the fixed ratio (FR) component, mainly by increasing post-reinforcement pauses.
• Effects on the fixed interval (FI) component varied: one pigeon showed increased responding, the other showed little change.
• Changes in pausing behavior were the primary determinant of rate changes, indicating schedule-dependent effects of d-amphetamine.

Conclusions:

• d-Amphetamine's impact on behavior is contingent on the reinforcement schedule, not solely on the overall response rate.
• The drug differentially affects pausing in pigeons depending on whether they are under fixed ratio or fixed interval conditions.
• These findings highlight the importance of schedule context in behavioral pharmacology research.