The three main dementias:
1)Alzheimer’s
2) Lewy Bodies
3) Vascular 

All three can occur at once.
Lewy bodies link to Parkinsons.                                       
Alzheimer’s- revisit

Each memory is strong. Associated dopamine to every memory. Memory recorded through the prefrontal cortex. Dopamine levels are heightened. Somatostatin is low. Dopamine is reward. Somatostatin is inhibitory. Therefore, a memory is taken back and forth between the hippocampus (at night) and the prefrontal cortex. The high level of dopamine builds a strong memory. The level of somatostatin fields the length of the duration of the memory with its inhibition qualities. The working together of these two promotes a strong memory.

These levels must be considered at the time of life that this activity occurs. Neprilysin clears the amyloid beta plaques in all people’s brains. A healthy brain has some amyloid beta plaques. When a person is born, the Alzheimer’s condition is already decided later in life. Somatostatin is a substrate of Neprilysin. If there is a shortfall in somatostatin this is a major marker in Alzheimer’s.

To add to this this, insulin degrading enzyme affects (degrades) amyloid beta and   degrades insulin. Somatostatin is the substrate of insulin degrading enzyme. If this is unable to do its job, there are serious consequences. Out of the two inhibited levels it means that amyloid beta has little restrictions and plaques begin to form. Insulin is also a problem because it shares the same receptors as amyloid beta. Buildup eventually governs most receptors leaving the insulin with nowhere to bind to. This means that insulin resistance and type 2 diabetes can occur. Therefore, plaques feature in Alzheimer’s. However, this is not the only problem. Once dopamine levels begin to dwindle it means retrieving memories become challenging because of the high levels they were formed on. A memory can be bought back with similar levels. Sometimes by describing a scenario to someone who suffers from the condition is enough to concentrate dopamine levels and achieve a positive outcome. Low levels of somatostatin do not help the cause either. Memories also need a level of inhibition. With higher dopamine an individual possibly gets high serotonin, cortisol, glutamate and even endorphins. It significantly drops acetylcholine which plays a major part in memory (REM sleep) and acts as a neurotransmitter. It binds muscarinic receptors and nicotinic receptors. Depletion of acetylcholine can cause anger, anxiety, psychosis, and hallucinations. Dopamine and somatostatin both display negligible levels in the advanced Alzheimer’s brain.

The second dementia is Lewy Bodies.