ABSTRACT
If you have previously taken, or are now taking, a psychology course, you likely have already heard of Patient H.M., an individual whose life-saving neurosurgery left him with complete anterograde amnesia. The medial temporal lobectomy, performed in 1953 to relieve severe epileptic seizures, removed the majority of his hippocampus, a brain region now known as critical to declarative memory formation. Every meeting with doctors, including those he saw regularly after his surgery, was a new set of introductions. His memory prior to the surgery appeared mostly intact, as did another aspect of memory that proved quite interesting to cognitive neuroscientists: Procedural memory. Psychologist Dr. Brenda Milner and her colleagues began having Henry perform learning tasks that typical individuals show gradual improvements on, such as the mirror-drawing task. While he would cite every experience as a new situation he had never seen before, Henry did, in fact, show steady improvement with each repeated trial of these tasks, demonstrating that although he could not consciously report having learned this, his brain was indeed forming new connections and new memories outside of his awareness. Continuing to work with researchers throughout his life until his death in 2008, and further donating his tissues to ongoing research, Henry’s contributions to cognitive neuroscience are unforgettable, and changed the entire field’s approach to the study of memory. While the hippocampus is still considered to be the main memory center of the brain, targeted for the study of cognitive disorders such as Alzheimer’s disease, Henry’s ability to continue learning retroactively confirmed Karl Lashley’s experimental studies on cortical involvement in memory: Memory most certainly involves numerous brain regions working together.
