The role of the hippocampus in learning and memory has been examined for many years. Studies have used rats, monkeys, and other animals and given them a variety of lesions to the hippocampus and other parts of the brain. These were followed by a variety of tests that involved learning and memory. Although most of the tests showed a correlation between injury to the hippocampus and affliction to learning and memory, the extent of the testing and the detail to which is has been studied gives a much larger picture of the possibilities for human comparison.
             Olton, D.S. & Samuelson, R.J. (1976). Remembrance of places past: Spatial memory in
             rats. Journal of Experimental Psychology: Animal Behaviour Processes, 2(2),
             Olton and Samuelson completed six experiments for their study of rats and spatial memory. All experiments used a radial arm maze for testing. The first three involved placing the rats in the maze to explore and search for food. A variety of changes were made in each experiment to test spatial memory. The results of these tests showed that one the rats began to run into the arms of the maze, changes had no effect on the accuracy of choice.
             Experiment four was concerned with the memory element of which arm had been chosen previously. The authors made changes in the maze, and they studied the data from a number of angles. The rat's memory processes while problem solving was studied. Experiment five increased the number of choices, resulting in a reduction in accuracy, and experiment six tested the sequence of changes made in the maze and whether the rats could quickly recover choice accuracy.
             Overall results show that rats can remember which arm of the maze they have already chosen, but this is affected by both the increase in the number of choices and the length of time between repetitions of choices. The rats treated each arm as a separate space and stored the information in the same manner. ...