Hockenbury Discovering Psychology 5th txtbk

264 CHAPTER 6 MemoryIn terms of our understanding of the memory trace, what do these findings suggest?Although there are vast differences between the nervous system of a simplecreature such as Aplysia and the enormously complex human brain, some tentativegeneralizations are possible. Forming a memory seems to produce distinct functionaland structural changes in specific neurons. These changes create a memorycircuit. Each time the memory is recalled, the neurons in this circuit are activated.As the structural and functional changes in the neurons strengthen the communicationlinks in this circuit, the memory becomes established as a long-term memory(Kandel, 2006).Creating New Synaptic Connections Formingnew memories involves strengtheningexisting synaptic connections and creatingnew synaptic connections between neuronsin the brain. Neuroscientist MichaelColicos and his colleagues at the Universityof California–San Diego (2001) photographedstructural changes in a singlehippocampus neuron that occurred inresponse to repeated electrical stimulation.The spidery blue lines in the photo arephysical changes in the neuron’s structurethat represent the first steps toward theformation of new synaptic connectionswith other neurons.Processing Memories in the BrainClues from AmnesiaKey Theme• Important insights into the brain structures involved in normal memoryhave been provided by case studies of people with amnesia caused bydamaged brain tissue.Key Questions• Who was H.M. and what did his case reveal about normal memoryprocesses?• What brain structures are involved in normal memory?• What are dementia and Alzheimer’s disease?amnesia(am-NEE-zha) Severe memory loss.retrograde amnesiaLoss of memory, especially for episodicinformation; backward-acting amnesia.memory consolidationThe gradual, physical process of convertingnew long-term memories to stable, enduringmemory codes.anterograde amnesiaLoss of memory caused by the inability tostore new memories; forward-actingamnesia.Disrupting the Consolidation of MemoriesHead injuries are common in football andmany other sports. In one study, footballplayers who were questioned immediatelyafter a concussion or other head injurycould remember how they were injuredand the name of the play just performed.But if questioned 30 minutes later for thesame information, they could not. Becausethe head injury had disrupted the memoryconsolidation process, the memories werepermanently lost (Yarnell & Lynch, 1970).Prior to the advent of today’s sophisticated brain-imaging technology, researchersstudied individuals who had sustained a brain injury or had part of their brain surgicallyremoved for medical reasons. Often, such individuals experienced amnesia,or severe memory loss. By relating the type and extent of amnesia to the specificdamaged brain areas, researchers uncovered clues as to how the human brainprocesses memories.Retrograde AmnesiaDisrupting Memory ConsolidationOne type of amnesia is retrograde amnesia. Retrograde means “backward moving.”People who have retrograde amnesia are unable to remember some or all of theirpast, especially episodic memories for recent events. Retrograde amnesia oftenresults from a blow to the head. Boxers sometimes suffer such memory losses afteryears of fighting. Head injuries from automobile and motorcycle accidents areanother common cause of retrograde amnesia. Typically, memories of the eventsthat immediately preceded the injuryare completely lost, as in the case ofaccident victims who cannot rememberdetails about what led up to theaccident.Apparently, establishing a longtermmemory is like creating a Jell-Omold—it needs time to “set” before itbecomes solid. This process of “setting”a new memory permanently inthe brain is called memory consolidation(McGaugh, 2000). More specifically,memory consolidation is thegradual, physical process of converting