Alzheimer’s in the Brain


Alzheimer’s Disease (AD) accounts for around 60% of dementia cases. It is a progressive, degenerative disease affecting the brain. AD is barely noticeable at first, making it hard to diagnose. If caught in its early stages, individuals are often diagnosed with Mild Cognitive Impairment (MCI).


Symptoms of MCI can include: losing one’s train of thought, problems finding words and impaired decision making. Whereas symptoms of progressive AD consist of: episodic and semantic memory deficits; issues controlling thought and behaviour, and personality changes


AD can be assessed using a Mini Mental State Examination (MMS), in which simple tasks are used to assess orientation, attention, short term memory, long term memory and language.


There are two types of AD:

  • Early onset AD (familial)– caused by mutations in the Presenilin 1, 2 and beta-amyloid, along with chromosome-14. These mutations cause a build-up of beta-amyloid plaques in the brains of affected individuals, leading to brain atrophy.
  • Late Onset AD – The gene APOE can come in two forms: AP02, AP03 and AP0E4. It is thought that having one copy of APOE4 increases the risk of AD by about four times and two copies by 10-20 times.


Key Terms

Mild Cognitive Impairment (MCI) – A brain deficit in which the individual has a mild memory problems, which is diagnosed dependent on the individual’s ability to function as usual in day to day life. (Dementia is diagnosed when memory loss has progressed to a point of not normal independent function).

Dementia – describes an array of symptoms (usually caused by brain damage) that include memory loss, cognitive difficulties, and problems with language.

Episodic Memory – an individual’s memory of a specific event such as how they felt in a certain situation or the time and place of an event.

Semantic Memory – a portion of long term memory involved in knowledge not derived from personal experience such as the sounds of letters and capitals of countries.

Presenilin 1, 2 and beta-amyloid – genes that when mutated may cause early onset AD.

Gene – A section of DNA that provides the instructions to build and maintain our bodies.

Beta-amyloid plaques – clumps of protein fragments that are toxic to neurons and their connections.

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