Memory Disorders Part 2 Flashcards
Alzheimer’s disease
- Progressive disorder that results in dementia and death
- Early symptoms: selective declines in memory (mild cognitive impairment)
- Later symptoms: confusion, irritability, anxiety, and deterioration of speech
- Advanced stages: difficulties with even simple responses (eg. Swallowing, bladder control)
- Strong genetic component – if your parents have it, you have a 50% chance
3 defining characteristics of Alzheimer’s
- neurofibrillary tangles
- amyloid plaques
- decrease in brain volume
defining characteristics: neurofibrillary tangles
Microtubules become hyperphosphorylated (more phosphate), breaking them down and leading to tau tangles
defining characteristics: amyloid plaques
- Scar tissue; first signs of Alzheimer’s
- Amyloid normally involved in plasticity
- First seen in temporal lobe (in parts involving memory, ie. Hippocampus)
defining characteristics: decrease in brain volume
Substantial decrease in brain volume due mainly to loss/shrinkage of neuronal processes (synapse loss), but also due to loss of neurons
Alzheimer’s biomarkers
- Low beta-amyloid levels in cerebrospinal fluid
- High tau levels in cerebrospinal fluid
- PET imaging of beta-amyloid levels
- PET imaging of tau and hyperphosphorylated tau
- Decrease in hippocampal volume (MRI)
- Decreases in brain metabolism – becomes hypoactive; uses less glucose (FDG-PET)
2 theories of pathogenesis
- neurofibrillary/tau hypothesis
- amyloid cascade hypothesis
theories: neurofibrillary/tau hypothesis
- Tau is causing degeneration & Alzheimer’s
- However, when testing this in animal models, it doesn’t cause amyloid plaques, so it might not be legit
theories: amyloid cascade hypothesis
- amyloid plaques causing Alzheimer’s
- Most widely-accepted hypothesis
- Brains of people with Downs Syndrome produce more plaques, and those people have much higher rates of Alzheimer’s than the rest of the population
- Issue: amount of plaques doesn’t always correlate with degeneration
treatment
- Cholinergic (ACh) agonists – eg. Acetylcholinesterase inhibitors
- NMDAR (glutamate) antagonist (memantine)
- Lithium
- Physical exercise, environmental enrichment -> slows down deterioration