Cholinergic modulation of the content of temporal memory.

The pharmacological effects of anticholinesterases (physostigmine and neostigmine) and cholinergic receptor blockers (atropine and methylatropine) on the content of temporal memory in the rat were studied with the use of a 20-s peak-interval procedure with auditory signals. Physostigmine administered ip decreased the variability of the temporal discrimination and shifted peak times permanently leftward on the time scale in a dose-dependent fashion (0.01, 0.03, & 0.09 mg/kg). Neostigmine (0.03 mg/kg) did not produce any of these effects. Atropine administered ip increased the variability of the temporal discrimination and shifted peak times permanently rightward on the time scale in a dose-dependent fashion (0.05, 0.15, & 0.45 mg/kg). Methylatropine (0.15 mg/kg) did not produce any of these effects. Application of a scalar timing model indicated that physostigmine decreased the remembered times of reinforcement and increased sensitivity to time, whereas atropine increased the remembered times of reinforcement and decreased sensitivity to time. These results suggest that the effective level of brain acetylcholine sets the communication speed for the translation of durations measured by the internal clock into values stored in temporal memory.