Cognitive decline predicted by brain imaging

A study reported that the degeneration of the basal nucleus of Meynert predicted cognitive decline in Parkinson’s disease patients.

The basal nucleus of Meynert is an acetylcholinergic neural group in the basal forebrain. It is thought to provide other forebrain structures with acetylcholine which is thought to keep us alert and ready to learn. The basal nucleus is frequently damaged in conditions such as Parkinson’s disease or Alzheimer’s disease.


Approximate location of the basal nucleus in a sagittal section of the human brain.

A recent study showed that the degeneration of the nucleus basalis predicts the deterioration of cognitive functions in Parkinson’s disease patients. The study included more than 300 patients with Parkinson’s disease and around 150 healthy controls. The researchers collected data for 3 years by imaging the brain of the participants and completing the Montreal Cognitive Assessment test with them every 6 months.

They used magnetic resonance imaging which is now a basic method in medicine. It is based on nuclear magnetic resonance, the property of atomic nuclei to absorb and re-emit electromagnetic radiation in strong magnetic fields. The concrete imaging method used (T1 weighted imaging) registers the highest signal density in fatty tissues and the lowest in watery compartments, thus the brain appears bright, while the ventricles, containing cerebrospinal fluid, appear black. The pictures generated in this way may be used to discern damage in the nervous system.


Pictures of the brain generated with magnetic resonance imaging By KieranMaher at English Wikibooks [Public domain], via Wikimedia Commons

The magnetic resonance imaging data was also used to assess the integrity of neural pathways. The method enabling this is called diffusion tensor imaging. The magnetic resonance data is collected in sequence to assess the flow of fluids in the brain. As the flow is determined by white matter tracts of the brain (these connect the distant neuron populations of the brain), the diffusivity index is highly informative about the state of these tracts and it is thus suitable to detect pathologic changes.

The Montreal Cognitive Assessment (MoCA) is a standardized test, a tool to assess cognitive impairment. It contains several tasks assessing for example the learning and recall of words, the ability to draw an object from memory or to copy one, and the ability to do basic arithmetic operations.

The data showed that the degree of pathology in the basal nucleus correlated with the severity of cognitive impairment. As the researchers collected imaging data and test scores at several different time points, they were also able to show that degenerative changes in the basal nucleus usually predate the decrease of MoCA test score. This relationship may serve to predict cognitive decline in Parkinson’s disease patients and thus improve patient care. The finding will also serve future studies aiming to understand the causes and progression of cognitive decline in Parkinson’s disease.


Nature Reviews Neurology – Vol. 14 Issue 6 – Prediction of cognitive decline in PD