amyloid plaque

synonyms: neuritic plaque, senile plaque
https://doi.org/10.1351/goldbook.11582
Structure representing extracellular deposition of $\ce{\upbeta\!\mbox{-}amyloid protein}$ in the gray matter of the brain that occurs with aging and in increased amount in Alzheimer disease.
Source:
PAC, 2015, 87, 841. (IUPAC Glossary of terms used in neurotoxicology (IUPAC Recommendations 2015)) on page 846 [Terms] [Paper]