Aging Normal aging vs neurodegeneration Human behavior slower working memory less flexibility sensory decrements semantic memory OK better emotional regulation Rat behavior harder to motivate poorer spatial abilities working memory Human neural aging subcortex unknown shrinkage of cerebral cortex neuron loss 10 between 20s and 90s cortex loss of dendrites synapses in prefrontal cortex 0 50 shrinkage of hippocampus neuron loss unknown shrinkage of white matter myelin axons Dendritic spines Spines excitatory synapses Non human neural aging Cortex regional neuron loss in cortex rats monkeys loss of dendrites dendritic spines synapses rats monkeys Hippocampus rats no loss of neurons variable loss of dendrites synapses White matter no loss in rats Rats have less neural loss during aging than humans Dementia Global cognitive failure behavioral disorganization loss of memory 50 of people over 85 years Types Alzheimer s most common plaques amyloid and neurofibrillary tangles especially in cortex and hippocampus starts with loss of cholinergic input Decrease in brain weight Most in hippocampus and cortex Uylings deBrabander 2002 Hypothesis neurons stop working and die Neurocognitive reserve Other dementias Lewy body dementia Lewy body neurofilament clumping Starts with Parkinson symptoms but degenerates quickly with dementia as well Less obvious neural degeneration than Alzheimer s Vascular dementia Caused by mini strokes or mini bleeds Variable symptoms Frontal temporal dementia
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