Cholesterol is a key to learning and memory. However, high cholesterol has different effects depending on your age and other factors.
Cholesterol is vital to normal brain function including learning and memory but that involvement is as complex as the synthesis, metabolism, and excretion of cholesterol itself. Dietary cholesterol influences learning tasks from water maze to fear to condition even though cholesterol does not cross the blood-brain barrier. Excess cholesterol has many consequences including peripheral pathology that can signal the brain via cholesterol metabolites, pro-inflammatory mediators, and antioxidant processes.
Manipulations of cholesterol within the central nervous system through genetic, pharmacological, or metabolic means circumvent the blood-brain barrier and affect learning and memory but often in animals already otherwise compromised. The human literature is no less complex. Cholesterol reduction using statins improves memory in some cases but not others.
There is also controversy over statin use to alleviate memory problems in Alzheimer's disease. Correlations of cholesterol and cognitive function are mixed and association studies find some genetic polymorphisms are related to cognitive function but others are not. In sum, the field is in flux with some seemingly contradictory results and many complexities. Nevertheless, understanding cholesterol effects on learning and memory is too important to ignore.