d-amphetamine and fixed-interval performance: effects of operant history

Area of Science:

• Behavioral neuroscience
• Animal behavior studies

Background:

• Reinforcement schedules shape animal behavior.
• Prior conditioning can influence subsequent responses to stimuli and drugs.

Purpose of the Study:

• To investigate how different reinforcement histories affect behavior under a fixed-interval schedule.
• To determine if these histories alter the effects of d-amphetamine.

Main Methods:

• Rats were exposed to fixed-ratio 40 or interresponse-time-greater-than-11-second schedules.
• Rats were then shifted to a fixed-interval 15-second schedule.
• The effects of d-amphetamine were assessed at different time points.

Main Results:

• Rats with fixed-ratio histories showed higher rates of lever pressing than those with interresponse-time histories.
• This difference persisted over extended exposure to the fixed-interval schedule.
• d-amphetamine increased low-rate responding and decreased high-rate responding, depending on the reinforcement history.

Conclusions:

• Response rate under a fixed-interval schedule is influenced by prior reinforcement history.
• This history is a key factor in determining the effects of d-amphetamine on behavior.