Four of the five drugs approved to treat the symptoms of Alzheimer’s disease are cholinesterase inhibitors. Although scientists know that these pharmaceuticals stop the breakdown of the neurotransmitter acetylcholine, why this helps Alzheimer’s patients has not been clear.
In this study, researchers found that the increased level of acetylcholine allows signals to enter the brain with more precision and less background noise. These effects are seen primarily in the sensory cortices, the gatekeepers of the brain that begin a signal’s propagation through the neural network.
To determine this, 13 healthy young adults received doses of galantamine, a common Alzheimer’s drug. Two electroencephalographs, or EEGs, were taken – one with the drug and one without – as the participants focused on a simple concentration task while listening to a series of modulating tones.
The researchers were seeking differences in neural activity between the two drug states in response to unexpected changes in the sound patterns that the participants were hearing. The scientists compared the results to 10 computer models based on the different effects the drugs could have on the brain. The model that best fit the results suggested that it was the low-level wheels of the brain early on in the neural networking process that were benefitting from the drugs and creating clearer signals.
Rosalyn Moran, PhD
Understanding why certain Alzheimer’s drugs improve a patient’s symptoms could lead to the development of new and better treatments.
What You Should Know:
The computer models the researchers used to characterize the effects of the Alzheimer’s drugs were based on the Free Energy Principle, a Bayesian brain theory that describes the basic rules of neuronal communication and explains the creation of complex networks. The theory hypothesizes that neurons seek to reduce uncertainty, which can be modeled and calculated using free energy molecular dynamics. Connecting tens of thousands of neurons behaving in this manner produces the probability machine known as the human brain.
Turning Alzheimer’s fuzzy analog signals into high definition
Where to Find It:
Moran RJ, Campo P, Symmonds M, Stephan KE, Dolan RJ, Friston KJ. Free energy, precision, and learning: The role of cholinergic neuromodulation. J Neurosci, 2013; 33(19):8227–36.