Complex sentence: The hippocampus is an area of the brain integral to learning and memory; removal of this structure can result in the inability to form new memories (i.e. anterograde amnesia) as most famously demonstrated in a patient referred to as HM.
Split into simpler sentences: The hippocampus is an area of the brain integral to learning and memory. Removal of this structure can result in the inability to form new memories (i.e. anterograde amnesia) as most famously demonstrated in a patient referred to as HM.