This chapter focuses on chronic disorders of memory capacity and interventions to treat them. These include anterograde and retrograde amnesia and impairments in working, spatial and prospective memory. It addresses differences between therapy and enhancement in memory modification. The chapter also considers deep brain stimulation as an experimental treatment for memory impairment in early-stage Alzheimer’s disease, weighing benefits and risks. It explains why devices external to the brain could not replace it as the source of memory. The chapter then explores the potential of a hippocampal neural prosthetic to improve memory encoding and retrieval for people with damaged hippocampi. It also explores the possibility of a prosthetic that would completely replace the hippocampal complex and whether it could decode the cognitive and emotional content of episodic memories.