An automated method for studying drug effects on problem solving by small laboratory animals.
The design and construction details of a method for studying problem solving by small animals is described. The form of motivation is escape from water in a T-shaped apparatus, thus eliminating possible confounding effects involved when food or water intake is restricted below normal. The arm of the T in which escape is possible is alternated from trial to trial. Two levels of problem solving are evaluated: an animal can minimize escape time during a series of trials by alternating its responses, i.e., 100% reinforcement; alternatively, it may choose the same alley on each trial, which results in only 50% reinforcement. The time to make the decision and the total time are automatically recorded. We have demonstrated the sensitivity of the method to hypofunctioning of the cholinergic neurotransmitter system, an analogy to behavioral changes accompanying progressive degenerative dementia. Two effects of the hypocholinergic state were especially notable: animals in this state have significantly greater difficulty in shifting from the "primitive" position habit to the more complex alternation solution, and preliminary experiments suggest that certain pharmacological treatments may be effective in overcoming this deficiency.