Rogers & Kesner (2003)

Question 1

What is a…

Neurotransmitter?

Answer 1

A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.

Question 2

Aim

Answer 2

To determine the role of acetylcholine in the formation of spatial memory

Question 3

Method

Answer 3

• They had 30 rats become accustomed to a Hebb-Williams maze by placing food in one of the corners until the rats were no longer afraid of the environment
• The rats were then either injected with scopolamine or a saline solution ten minutes before running the maze
• Scopolamine blocks the acetylcholine receptor thus inhibiting any response
• The saline solution acts as a placebo injection as even receiving the injection can result in an increase in adrenaline which would be a confounding variable
• The injections were made directly into the hippocampus

Question 4

Findings

Answer 4

• Encoding of memory was assessed by comparing the average number of errors made on the first 5 trials of day 1 to the last 5 trials of day 1.
• Retrieval was assessed by comparing the average number of errors made on the first 5 trials of day 2 to the last 5 trials of day 1.
• The scopolamine group took longer and made more mistakes in the learning of the maze.
• Higher average number of mistakes on the last five trials on Day 1.
• No effect on the retrieval of memories that had already been created.

Question 5

DP Psychology Example

Answer 5

DP Psychology Example:

Neurotransmission is the process where neurons communicate with other neurons. This is done when the presynaptic neuron releases chemicals called neurotransmitters to cross the gap between two neurons called the synapse. These neurotransmitters then bind to specific receptor sites on the postsynaptic neuron creating an electrical signal called the action potential. If these receptor sites are blocked by another chemical the postsynaptic neuron will not be able to create an action potential, inhibiting the process of neurotransmission. This is a common way of studying the effects of neurotransmission, blocking the receptor sites of a specific neurotransmitter and then noting behavioral changes.

In some patients with memory problems, we see a lower rate of activity in the hippocampus. This could be because of a lack of a neurotransmitter called acetylcholine. As it is not possible to directly observe the activity of neurotransmission in the brain, and it would be unethical to manipulate levels of acetylcholine in a patient, animal research is used with the hope of better understanding human behavior.

Rogers and Kesner carried out a study on the effects of acetylcholine on spatial memory. To do this they tested rats ability to learn a maze. Firstly, the rats were acclimated to the maze, so that distress caused by a new environment would not be a confounding variable and influence the ability to create memories. Then, the rats were allocated to one of two conditions. In one group, they were injected with scopolamine, a chemical known to block acetylcholine receptor sites. In the second group, they were injected with a placebo, a saline solution with no active ingredient to control for an adrenaline increase from the stress of an injection. The researchers then had the rats run the maze again. The researchers found that the group injected with scopolamine performed significantly worse on the maze, taking longer to learn it and making more mistakes. This allowed the researchers to conclude that acetylcholine plays a role in the consolidation of spatial memory in the hippocampus. These findings were later supported in tests on humans such as Antonova’s virtual reality study where she also tested the impact of inhibiting acetylcholine receptor sites on spatial memory in people and found results that appeared to support Rogers and Kesner’s conclusions.