Provided is the discovery of the role of EphA4 signaling in neurodegenerative disorders involving β-amyloid induced neurotoxicity such as Alzheimer's Disease. New therapeutic methods, therapeutic agents, and kits for treating diseases caused or exacerbated by overactivated EphA4 signaling are provided. Also provided are methods for identifying additional compounds as therapeutic agents useful for treating conditions involving overly active EphA4 signaling.