Document Type


Degree Name

Master of Arts (MA)




Faculty of Science

First Advisor

Angelo Santi

Advisor Role

Thesis Supervisor


This study describes the effects of cholinergic and dopaminergic drugs on time and number processing by rats. Rats were trained to discriminate discrete sound sequences. On number trials, the duration of the sound sequence was a constant 4 seconds and the number of sounds was 2 or 8. On time trials, the number of sounds was held constant at 4, and the duration of the sound sequence was either 2 or 8 seconds. Psychophysical functions for number and time were obtained by presenting unreinforced sequences of intermediate number and duration. Accuracy of performance was greater with temporal signals than with numerical signals. The general dopamine agonist methamphetamine (1.5 mg/kg) and the specific D2 agonist quinpirole (0.08 mg/kg) significantly reduced control by time and number without shifting the psychophysical functions leftward (p<.05). The cholinergic antagonist scopolamine (0.1 mg/kg) significantly reduced accuracy at longer durations and higher numbers, but not at lower values of time or number (p<.05). Under all three drugs, the psychophysical functions for time and number showed a decrease in signal discriminability. The cholinergic agonist nicotine (0.2 mg/kg) significantly shifted the psychophysical function rightward for time and number (p<.05). This similarity of the effect of each drug on both time and number processing is consistent with the idea that the same internal mechanism is used for timing and counting. However, the specific effect of each drug on timing and counting was not consistent with previous descriptions of the role of different neurotransmitter systems on the perception of time and number.

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