Most of the (few) approved Alzheimer’s drugs are cholinesterase inhibitors — that is, they stop the breakdown of the neurotransmitter acetylcholine. A new study explains why they help. It appears they allow signals to enter the brain with more precision and less background noise.
The study involved 13 healthy young adults, some of whom were given the cholinesterase inhibitor galantamine, before listening to a series of modulating tones while focusing on a simple concentration task. The patterns of neural activity demonstrated by those on the drug most closely fit a model in which the signals coming into the brain were sharpened. This was something of a surprise, since it has been generally assumed that the effects would be most pronounced in the ‘higher-order’ processing regions.
The findings are an interesting reminder of the importance of sensory perception for optimal cognition. It should be noted, though, that this sharpening of the signal did occur in an environment in which the stimuli were predictable.
 . Free Energy, Precision and Learning: The Role of Cholinergic Neuromodulation. The Journal of Neuroscience [Internet]. 2013 ;33(19):8227 - 8236. Available from: http://www.jneurosci.org/content/33/19/8227