Hockenbury Discovering Psychology 5th txtbk

The Search for the Biological Basis of Memory265new long-term memories to stable, enduringmemory codes (Medina & others,2008). If memory consolidation is disruptedbefore the process is complete, thevulnerable memory may be lost (Dudai,2004).In humans, memory consolidationcan be disrupted by brain trauma, such asa sudden blow, concussion, electricshock, or encephalitis (Riccio & others,2003). Similarly, many drugs, such as alcoholand the benzodiazepines, interferewith memory consolidation. In contrast,stimulants and the stress hormones thatare released during emotional arousaltend to enhance memory consolidation(McGaugh, 2000).Anterograde AmnesiaDisrupting the Formation of Explicit MemoriesAnother form of amnesia is anterograde amnesia—the inability to form new memories.Anterograde means “forward moving.” The most famous case study ofanterograde amnesia lasted over 50 years. It was of a man who for years was knownonly by his initials—H.M. But the need to protect H.M.’s privacy ended whenHenry Molaison died at the age of 82 on December 2, 2008.In 1953, Henry was 27 years old and had a 10-year history of severe, untreatableepileptic seizures. Henry’s doctors located the brain area where the seizures seemed tooriginate. With no other options available at the time, the decision was made to surgicallyremove portions of the medial (inner) temporal lobe on each side of Henry’s brain,including the brain structure called the hippocampus (Scoville & Milner, 1957).After the experimental surgery, the frequency and severity of Henry’s seizureswere greatly reduced. However, it was quickly discovered that Henry’s ability toform new memories of events and information had been destroyed. Although theexperimental surgery had treated H.M.’s seizures, it also dramatically revealed therole of the hippocampus in forming new explicit memories for episodic and semanticinformation.Psychologists Brenda Milner and Suzanne Corkin studied Henry extensively overthe past 50 years (Corkin, 1984; Milner, 1970; Scoville & Milner, 1957). If you hadhad the chance to meet Henry, he would have appeared normal enough. He had agood vocabulary and social skills, normal intelligence, and a delightful sense of humor.And he was well aware of his memory problem. When Suzanne Corkin (2002) onceasked him, “What do you do to try to remember?” Henry quipped, “Well, that I don’tknow because I don’t remember (chuckle) what I tried.”Despite superficially appearing normal, Henry lived in the eternal present. Hadyou talked with Henry for 15 minutes, then left the room for 2 or 3 minutes beforecoming back, he wouldn’t remember having met you before. Although some of thepsychologists and doctors had treated Henry for years, even decades, Henry wasmeeting them for the first time on each occasion he interacted with them (Ogden& Corkin, 1991; Corkin, 2002).For the most part, Henry’s short-term memory worked just fine. In fact, hecould fool you. If Henry actively repeated or rehearsed information, he could holdit in short-term memory for an hour or more (Nader & Wang, 2006). Yet justmoments after he switched his attention to something else and stopped rehearsingthe information, it was gone forever. However, Henry’s long-term memory waspartially intact. He could retrieve long-term memories from before the time he was16 years old, when the severe epileptic seizures began.Henry Gustav Molaison: The Real H.M.(1926–2008) At the age of 9, Henry was hithard by a bicyclist and jarred his headbadly. Not long after, Henry beganexperiencing seizures. By early adulthood,Henry’s seizures had increased in bothseverity and frequency. In an effort tocontrol the seizures, Dr. William BeecherScoville performed an experimentalsurgery, removing the hippocampus andamygdala on each side of Henry’s brain.It was the first—and last—time that thesurgical procedure would be performed.Because of the profound anterogradeamnesia caused by the surgery, Henrybecame one of the most intensive case studiesin psychology and neuroscience. Over thenext half century, Henry participated in hundredsof studies that fundamentally alteredthe scientific understanding of memory.Henry died on December 2, 2008, buthis contributions to science continue. Neuroscientistsat the Brain Observatory at theUniversity of California–San Diego continueto study Henry’s brain, which wasremoved shortly after his death. Eventually,a complete atlas of Henry’s brain willbe available online.Suzanne Corkin Since the mid-1960s, MITneuropsychologist Suzanne Corkin hasevaluated different aspects of Henry’smemory abilities. In looking back onHenry’s life, Corkin (2002) commented,“We all understand the rare opportunitywe have had to work with him, and weare grateful for his dedication to research.He has taught us a great deal about thecognitive and neural organization of memory.We are in his debt.”