Note. In current theory, the "brown fibers" are misfolded and misformed proteins generated inside the neuron cell. And then the misformed are ejected either as debris or else as dead cell fragments to accumulate as amyloid plaque in Alzheimer's Disease. See FB Support group for Alzheimer's Disease. To rub the point in, note our little neuron friend has some "brown" misformed proteins already inside, thought to be misfolded from protein glycation from excessive sugars as cited already.