The neurotransmitter acetylcholine has already been established as being crucial for learning and memory. In a study with rats, Norman Weinberger, research professor of neurobiology and behaviour, and colleagues determined that a higher level of acetylcholine during a learning task correlated with more details of the experience being remembered. The results are the first to tie levels of acetylcholine to memory specificity and could have implications in the study and treatment of memory-related disorders.
"This is the first time that direct stimulation of a brain region has controlled the amount of detail in a memory," said Weinberger, a fellow at University of California – Irvine´s (UCI) Center for the Neurobiology of Learning and Memory. "While it is likely that the brain uses a number of mechanisms to store specific details, our work shows that the level of acetylcholine appears to be a key part of that process."
In their experiments, the researchers exposed rats to tones of various frequencies. During some of the trials, they paired one tone with stimulation of a section of the rats' brains known as the nucleus basalis, which relays commands to the auditory cortex by secreting acetylcholine. During some experiments, the stimulation of the nucleus basalis was weak, whereas in other animals the stimulation was stronger. When the tones were replayed the next day, the scientists could measure how well they remembered the various frequencies by measuring changes in their respiration rates.
The results showed that a weak activation of the nucleus basalis, which resulted in a small amount of acetylcholine being released, did lead the rats to remember the tones but not specific frequencies. However, when the stimulation was greater (leading to the higher level of acetylcholine release), the rats also remembered the specific frequencies.
MEDICA.de; Source: University of California - Irvine