In the hippocampus, there is a high concentration of acetylcholine receptor sites. Researchers have therefore questioned the role of this neurotransmitter in the consolidation of memories.

Before reading through the procedure and results below, you may want to watch the following video.  José Martinez has also worked with Raymond Kesner on similar research. The test paradigm that he describes in the video is outlined in a book edited by Martinez & Kesner in 1991 called Learning and Memory. 

The original study may be accessed here.

The aim of the study was to determine the role of acetylcholine in the formation of spatial memory.

Rogers & Kesner wanted to determine the role of acetylcholine in memory formation and retrieval. They had 30 rats acclimate to a Hebb Williams maze by placing food in one of the corners.  Once the rats were familiar with the maze - and no longer were afraid of the environment - the experiment could begin.

The rats were randomly allocated to one of two conditions. The rats were either injected with scopolamine or with a saline solution ten minutes before running the maze. Scopolamine blocks the acetylcholine receptor sites and thus inhibits any response.  The saline solution was a placebo injection. This was done to make sure that the fact of getting an injection alone was not responsible for a change in memory. An injection could result in an increase in adrenaline which would be a confounding variable. The injections were made directly into the hippocampus.

Encoding of memory was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day 1 was used to assess retrieval.

The findings were that the scopolamine group took longer and made more mistakes in the learning of the maze - that is, there was a higher average number of mistakes made on the last five trials on Day 1. However, it did not appear to have an effect on retrieval of memories that had already been created. It appears that acetylcholine may play an important role in the consolidation of spatial memories.

• The researchers used a rigorously controlled experiment with a placebo condition to avoid the effect of confounding (extraneous) variables.
• The study is able to establish a cause and effect relationship; however, it is a reductionist approach to understanding memory.  There are several different types of memory and the process of memory consolidation is very complex.
• The research could one day lead to the development of treatments for people suffering from dementia or Alzheimer's disease.
• Biologists believe that animals can serve as models for human physiology and behaviour; however, there are questions about the extent to which findings can be generalized to humans.

If you want to more about the Hebb Williams Maze and how it works - here is a quick video with a good explanation.