The influence of sequential information in rats: Learning, memory, and the effects of amnestic drugs

Tasks with embedded S-R (Stimulus-Response) sequences are commonly used to assess procedural memory in humans, but have not been used to the same extent in animals. Different degrees of embedded information, random or repeating S and/or R sequences, were incorporated into a conditional discrimination paradigm for rats. Experiment 1 showed that subjects trained with a repeating S-R conjoined sequence acquired the task faster than subjects trained with a random S-R sequence, and used the conjoined S-R pattern, rather than only the discriminative stimuli, to guide their behavior. Experiment 2 showed that scopolamine, diazepam, and lorazepam all interacted with the type of embedded information available in the task. Subjects trained with only a repeating S sequence were more sensitive to drug-induced impairments than subjects trained with only a repeating R sequence, who were in turn more sensitive to drug-induced impairments than subjects trained with a repeating S-R conjoined sequence.