ERK activity in the crab’s nervous system has also been shown to be relevant in memory impairment induced by beta-amyloid, a peptide originated by cleavage of amyloid precursor protein (APP) which is a major constituent of the neuritic plaques found in Alzheimer’s disease patients and is proposed to be the cause of memory deficit and neurodegeneration observed in this pathology. This evidence concerns the gene APP and Alzheimer disease.