MSFinals-3087

A 50-year-old man, presenting with changes in mood and behavior that have been developing over the past 8 years, is brought to the clinic by his son. The son also reports that his grandfather died from Alzheimer’s disease at the age of 52. The patient has recently experienced aphasia, disorientation, and memory loss. He passes away a few weeks later. A brain biopsy shows cortical atrophy with widening of the cerebral sulci.
What is the most probable mechanism that contributed to the development of this patient’s condition?