The aim of the study was to determine the role of acetylcholine in the formation and retrieval of memory. There were several tests done in this study. To simplify the study, we are going to look at only three of the tests that were given.
The sample was made up of 13 men aged 31 to 59, with a mean age of 39.2. All participants were tested for physical and mental health before undergoing the procedure. Participants were briefed on the potential side effects of scopolamine (dry mouth, forgetfulness, sedation and hallucinations) and were reminded throughout that they had the right to withdraw from the study.
Each participant underwent all three conditions. There was a placebo group in which they were injected with a saline solution. Then there was an injection of either 0.5 mg or 0.8 mg of scopolamine. There was a 48-hour pause between each condition and the conditions were counter-balanced. Although a placebo was given, the participants and the researcher immediately knew if it was the saline solution as there were no side effects.
The three tests were as follows:
- The Free Recall Test: After the injection, participants were read a list of 14 words - 7 were high imagery and 7 were low imagery. The participants were asked to recall the list immediately. The list was reread (in a different order) five times for a final potential score of 70. Then the participants were asked to recall the list again after a 40-minute delay.
- The New Map Test: Participants were given a map of a fictitious state and asked to memorize the locations of the cities. After 60 seconds they were given a blank map and a list of the cities. They were asked to put the cities on the map. This was repeated four times.
- The Remote Memory Battery: The participants were shown 150 images of famous faces and events to see if they could recognize them. Unlike the other tasks, this is based on LTM retrieval, not the transfer of memory from STM to LTM.
The findings showed that scopolamine inhibited the encoding of new memories, but did not have a significant effect on the recall of long-term memories. It appears that acetylcholine plays a role in the encoding of both semantic and spatial memories. You can see the exact results below.
Test 1: Number of words recalled - immediate or delayed conditions
|Task||The placebo condition||0.5 mg of scopolamine||0.8 mg of scopolamine|
|Immediate recall (out of 70)||44.2||40.2||32.6|
|Delayed recall (out of 14)||7.5||5.8||3.1|
Test 2: Percent of locations correct on the map test
|Trial||The placebo condition||0.5 mg of scopolamine||0.8 mg of scopolamine|
Test 3: Average per cent of correct responses
|The placebo condition||0.5 mg of scopolamine||0.8 mg of scopolamine|