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Chapter 6

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PSYC 221
Yaroslav Konar

Page 148-167, 20 pages Page 1 of6 Chapter 6: Long-Term Memory – Structure DISTINGUISHING BTWN LTM & STM • Korsakoff’s Syndrome: Condition caused by prolonged deficiency of vitamin B1, usually as a result of chronic alcoholism. This deficiency leads to destruction of frontal and temporal lobes, causing severe memory impairment • Anterograde Amnesia: Loss of ability to retain new knowledge or memories – unable to recognize people he has just met, follow a story in a book. Retrograde Amnesia: Loss of memory for events that have happened in the past • Long-Term Memory (LTM): System responsible for storing large amounts of info for long periods of time, an “archive” about past events in our lives. STM is to RAM, working memory is to CPU, and LTM is to hard drive. Long-Term & Short-Term Processes • Recollections in LTM stretch from a few moments ago to years to decades back (long duration, large capacity). Recent memories tend to be more detailed, while with time these details fade with the passage of time and accumulation of other experiences • LTM not only retains information about the past, it operates dynamically to interact with working memory to create our ongoing experience; wealth of background information we are constantly consulting as we use working memory to process what is happening at a particular moment. • E.g. Tony’s friend Sarah says, “Jim and I saw the new James Bond movie last night”  Jim is the new guy Sarah met a month ago + Sarah is a big James Bond fan + I saw that movie, it was good. Serial Position Curve • Murdoch (1962): Subject hears a list of stimulus words being read (at 1 word every 2 seconds), and at the end must write down all the words heard, in any order. • Serial Position Curve: Percentage recall for each word against the word’s position in the list, e.g. how many words were remembered from the first 5 entries, middle 5, and last 5? • Memory is better for beginning and ends words than the middle. The primacy effect may exist because subjects have more time to rehearse these words and transfer them to LTM, particularly at the beginning when no other words are being attended to; as additional words are presented, less rehearsal is possible for later words • Rundus (1971): Presented list of 20 words at 1 word every 5 seconds, later asked to recall words. To some subjects, he asked them to repeat words out loud during the 5-second interval between words, but not told which ones to repeat. Indeed, subjects rehearsed words presented early in the list much more, which they were more likely to remember later. • Recency effect may occur since the most recently presented words are still in the STM/WM. • Glanzer & Cunitz (1966): Measure recall with subjects having to count backwards for 30 seconds between having heard the last word on the list and recalling (attention and WM occupied). This prevented rehearsal and allowed time for info to be lost from STM, such that the recency effect was eliminated. Coding in Long-Term Memory Page 148-167, 20 pages Page 2 of 6 • Auditory, visual, and semantic coding can occur for STM. LTM can also involve each of these types, such as visual coding to recognize someone’s face, auditory coding for someone’s voice, and semantic coding for remembering the meaning of an event in the past. • Semantic coding is the predominant type of LTM coding. • Sachs (1967): Participants listen to a tape recording of a message, then measure recognition memory with identification of a stimulus that was encountered earlier – specifically the exact wording of sentences in the passage, or the general meaning of the passage. • E.g. List of words including “house”, then present series of words including “house” and other words such as “table”. The subject must answer “yes” if the word was presented previously and “no” if it was not – this is different from recall where one would have to produce the item to be recalled. • Original sentence “He sent a letter about it to Galileo, the great Italian scientist” with option 1 being identical, option 2 as “Galileo, the great Italian scientist, sent him a letter about it” and option 3 as “He sent Galileo, the great Italian scientist, a letter about it.” • Most correctly identify 1 as identical and 2 as changed, but misidentified 3 as matching. The subjects remembered the sentence’s meaning instead of its exact wording. Locating Short & Long-Term Memory in the Brain • Experiments that compare where STM/WM and LTM are represented in the brain – there is both separation and overlap in brain regions Neuropsychological Studies • Dissociations can be used to draw conclusions from case studies of brain-damaged patients, including differentiating between STM and LTM where one function is affected but the other is spared. With two cases of opposite effects, a double dissociation can indicate that STM and LTM operate independently and are served by different mechanisms. • H.M. underwent lobectomy of the hippocampi, amygdala, and other structures to relieve seizures. He experienced retrograde and anterograde amnesia (LTM), but had normal LTM. • Clive Wearing similarly has functioning STM for the most recent 30 seconds, but is unable to form new LTMs. • Patient K.F. with opposite problem, suffered a stroke to the left parietal lobe. With a damaged phonological loop, normal LTM but poor STM as shown by a reduced digit span – span of 1 rather than between 5 and 8 digits. In addition, recency effect in serial position curve is reduced. Brain Imaging • Talmi (2005): Activation of different areas of the brain for STM and LTM tasks with fMRI. First presented list of words to subjects, but instead of asking to recall, they presented a single “probe” word that was either from near the beginning of the list (LTM), near the end (STM), or a novel word. The subject had to indicate whether the word had been presented before. • Probe words from the beginning of the list (LTM) activated brain areas associated with both LTM and STM – LTM to remember and transfer to STM during recall. In contrast, probe words from the end of the list only activated areas associated with STM. Accessing LTM requires activation of the STM/WM to be brought to awareness! Types of Long-Term Memory • Explicit Memory: Conscious or declarative memory. It consists of episodic memory for personal experiences and semantic memory with stored knowledge for facts. E.g. Going to cognitive psychology class memory, versus facts about theories of attention. Include recall and recognition tasks. • Implicit Memory: Non-declarative or unconscious memory. It consists of memories used without awareness, such that these cannot be reported. Includes priming with change in response to a stimulus caused by previous presentation of the same or a similar stimulus, such as recognizing familiar words. Also includes procedural or “skill” memory for doing things, such as typing. Finally, includes classical Page 148-167, 20 pages Page 3 of6 conditioning where an initially neutral stimulus is paired with another to result in the neutral stimulus taking on new properties EPISODIC & SEMANTIC MEMORY = EXPLICIT Distinguishing between Episodic & Semantic Memory • Distinguishing based on type of information remembered: events for episodic, facts for semantic. • Tulving (1985): Episodic memory involves mental time travel, to reconnect with events that happened in the past such as a trip to London. This experience is about self-knowing or remembering with putting oneself back in a situation – however, this does not guarantee the memory is accurate. • Semantic memory involves accessing knowledge about the world that need not be tied to a personal experience, such as facts, vocabulary, and concepts. Semantic memory is about knowing and does not involve mental time travel – e.g. can remember population size of London or historical facts, but not where I learned these things. The Separation of Episodic & Semantic Memory • Evidence that these two types of LTM are served by different mechanisms Neuropsychological Evidence • K.C. at age of 30 suffered severe damage to his hippocampus, and lost his episodic memory – unable to relive any of the events of his past, but he knows that certain things occurred (semantic remains). For example, he is aware his brother died two years ago, but cannot recall its circumstances or where he was when he heard about it. • The opposite scenario occurred to an Italian woman who suffered encephalitis. She experienced difficulty recognizing familiar people, and remembering the meaning of words on the shopping list or where things were located in a grocery store – all semantic memories destroyed. However, she could remember events in her life, such as what happened last week. • There is a double dissociation between episodic and semantic memory, using different mechanisms. • However, interpretation of neuropsychological cases is tricky since the extent of brain damage often differs from patient to patient, and the method of testing patients may differ between studies. Brain Imaging Evidence • Levine (2004): Subjects keep diaries on audiotape describing everyday personal events and facts drawn from semantic knowledge. When the subjects listen back to these tapes in an MRI scanner, the recordings of everyday events elicited detailed episodic autobiographical memories, while the factual recordings induced semantic memories. • Areas activated
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