Effects of D-amphetamine in a temporal discrimination procedure: selective changes in timing or rate dependency?

Area of Science:

• Behavioral pharmacology
• Neuroscience
• Animal behavior

Background:

• Amphetamine's effects on behavior are complex.
• Timing behavior is crucial for understanding cognitive processes.
• Existing models attempt to explain drug effects on timing.

Purpose of the Study:

• To investigate the effects of amphetamine on timing behavior in pigeons.
• To differentiate between rate dependency and a neuropharmacological model of timing.
• To assess amphetamine's impact on behavior under temporal discriminative control.

Main Methods:

• Two experiments using four pigeons.
• Behavior under discriminative control by time (5-30s durations).
• Acute d-amphetamine administration (0.1-3.0 mg/kg) and key-pecking response measurement.

Main Results:

• Amphetamine decreased high rates of key pecking and increased low rates, supporting rate dependency.
• Amphetamine did not shift timing functions leftward, contradicting the neuropharmacological model.
• Results were consistent across experiments, regardless of key color cues.

Conclusions:

• Findings support the rate dependency model for amphetamine's effects on timing.
• The neuropharmacological model of timing was not supported by these results.
• Amphetamine's influence on timing behavior is better explained by its general effects on response rates.