Visual and spatial trials paired in a new behavioral procedure: effects of benactyzine

A paired discrimination (PD) task in which visual and spatial discrimination trials were combined is offered as a method for the evaluation of drug effects on various behavioral parameters. Acquisition of the PD task is characterized by six different parameters simultaneously recorded each session. Analysis of memory requirements suggest that intact reference memory is involved in the performance of both types of trials while working memory is involved only in the performance of the spatial trial. Benactyzine (1-4 mg/kg), an anticholinergic drug, was tested for its effects on visual and spatial tasks presented either separately or in the PD combination. Benactyzine-induced mydriasis was also determined for its possible role in photophobic-induced errors. Benactyzine was found to differentially increase the number of errors performed during the spatial but not during the visual trials. The data are in accord with earlier finding of specific cholinergic involvement in working memory processes. Thus, low doses of benactyzine, and the PD task, can prove useful in the cognitive analysis of cholinergic hypofunction and its reversal by memory-enhancing drugs.