White matter lesions and the cholinergic deficit in aging and mild cognitive impairment

Area of Science:

• Neuroscience
• Neurology
• Radiology

Background:

• Alzheimer's disease (AD) is characterized by white matter lesions (WMLs) and cholinergic deficits, both linked to cognitive decline.
• WMLs, particularly in the periventricular regions, are associated with increased risk of dementia progression in mild cognitive impairment (MCI).
• Memory impairment in AD is partly attributed to a deficit in the cholinergic system.

Purpose of the Study:

• To investigate the relationship between WML load, cerebral acetylcholinesterase (AChE) activity, and memory performance in MCI due to AD.
• To determine if WML distribution influences cholinergic function and memory deficits.
• To compare the predictive power of AChE activity versus WML load for memory function.

Main Methods:

• Assessed WML load using the Scheltens scale in 17 MCI patients and 18 controls.
• Measured cerebral AChE activity via [11C]N-methyl-4-piperidyl acetate positron emission tomography (PET).
• Evaluated neuropsychological performance, focusing on memory function.

Main Results:

• Periventricular WML load, but not nonperiventricular, negatively correlated with AChE activity in both groups.
• Memory performance was associated with both periventricular and total WML load.
• AChE activity was a stronger predictor of memory function than WML load, gray matter atrophy, or age.
• The impact of WML load on memory was fully mediated by AChE activity.

Conclusions:

• The distribution of WMLs influences their contribution to cholinergic system dysfunction in MCI due to AD.
• AChE activity plays a crucial role in mediating the relationship between WMLs and memory deficits.
• Further pharmacologic studies are needed to explore the influence of WML distribution on response to cholinergic treatments.