WE ARE OUR BRAINS - CHAPTERS 18, 19, 20
CHAPTER 18 - ALZHEIMER'S DISEASE
"The prospect that you'll finally forget that you've forgotten everything and that this will no longer trouble you isn't a consoling thought, because it signifies your ultimate erasure as an individual."
Alzheimer's reverses the stages of development so that sufferers gradually lose their personality and their faculties, culminating in a state of complete dependence that leaves them curled up in a foetal position, demented and effectively brain-dead.
The "normal" brain ageing and Alzheimer's have a lot in common.
Alzheimer's can be seen as a premature, accelerated, severe process of brain ageing.
There are many forms of dementia, only post-mortem brain examinations can show if the individual had Alzheimer's.
Brain infarcts and haemorrhages can cause multi-infarct dementia which is similar to Alzheimers in its symptoms.
Parkinson's disease can also cause dementia.
AMYLOID CASCADE HYPOTHESIS
Risk factors result in the build-up of toxic amyloid beta peptides BA4 in the form of plaques, which are thought to alter transport proteins and make them stick together (tangles), thus disrupting cell function and causing the neuron to die. the infected neurons then pass on toxins, spreading the disease through the brain.
"Be nice to your kids, they'll chose your nursing home."
Alzheimer's travels through our brains by a fixed route:
1. Tangles in the entorhinal cortex, the cerebral cortex of the temporal lobe.
2. Abnormalities in the hippocampus cause memory problems to start.
3. The rest of the cerebral cortex is affected causing dementia.
4. The visual cortex is the very last to get damaged.
Functional losses occur in a fixed pattern, the reverse order in which we acquired them:
STAGE 1 - You still function normally
STAGE 2 - You start to lose things and find it hard to carry your job but can still maintain a semblance of normality.
STAGE 3 - Your coworkers notice you no longer handle difficult work tasks.
STAGE 4 - You have trouble with complex tasks, like handling financing.
STAGE 5 - You need help choosing what to wear.
STAGE 6 - (6a) help getting washed (6b) no longer can go to the toilet unaided (6c) have urinary incontinence (6d) foecal incontinence
STAGE 7 - (7a) you can only speak about half a dozen intelligible words (7b) you lose the power or speech (7c) you can no longer walk (7d) no longer sit unaided (7e) you can't smile (7f) you can't hold your head up (7g) you end up in bed curled up in foetal position. (if you insert a finger into their mouth at this stage, they will show a sucking relax, having at that point regressed fully to the condition of a newborn baby)
Music is retained until the latest stages of mental degradation, just as it is enjoyed in the earliest stages: newborns heal faster when played music and enjoy their mothers singing more than their talking to them.
Brian cells do not die en masse because of Alzheimer's: their death is only limited to certain regions of the brain: entorhinal cortex, part of the hippocampus, locus coreuleus and only occurs in advanced stages.
Reduced activity, which leads to neural shrinkage affects the entire brain from an early stage.
If the cells do not die, albeit being atrophied and nonfunctioning, it should be possible to reactivate the cells.
Use it or lose it = remain active mentally.
The biological clock is early on affected, which is why they don't receive their melatonin-peak in the nighttime and have difficulty going to sleep.
A combination of light therapy during the day, with melatonin pills help cognition and sleep rhythms.
It is very difficult to diagnose the level of pain that people with dementia are in because the autonomic system of pain reaction is impaired: their blood pressure and heart rate do not increase until they are in severe pain.
Pain itself is processed via two systems:
LATERAL SYSTEM: spinal chord, sensory input processing centre, which is intact, and so they process the pain signals normally: they have normal pain thresholds.
MEDIAL PAIN SYSTEM: spinal chord, cingulate cortex, this system is damaged, so they do not understand what is going on, and react in ways we do not associate with pain, such as appearing frightful and agitated.
CHAPTER 19 - DEATH
How the brain suffers from oxygen deprivation:
- The capillary cells, not neurons, are extremely sensitive to oxygen deprivation. After 4-5 minutes without oxygen they will swell so much, that even if the heart starts to beat again and breathing returns, the red blood cells can no longer get through the capillaries of the brain to give off oxygen.
- In the stages that follow, toxic substances are released and neurons die.
Brain cells can survive ten hours of oxygen deficiency.
CHAPTER 20 - EVOLUTION
The relative brain-body size has a correlation with the quality of the brain as in information-processing machine.
EQ, encephalisation quotient is a relative measure of an animal's brain weight on top of what is needed to regulate the body functions. It is alrgerly determined by the development of the cerebral cortex, the number of neurons there. There are groups of neurons called columns. Although the cerebral cortex grew through evolution, the cross sections of the columns remained identical, about half a millimetre. The number of columns increased in humans, brains grew bigger and convoluted in the process.
Bigger brain size - longer pregnancy - longer development and learning stages - longer life expectancy - fewer offspring.