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LTM: Systems
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- 1Background-Up to the late 60s and early 70s, the dominant view of memory was ‘unitarian’.
-“All learning is essentially of a kind – the modification of behaviour as the result of repeated stimulation under specified conditions” (Hunter, 1934:497) - 2So, what are memory systems?-The basis for an approach to memory research.
-Emphasis on ‘memory stores’ (this is where memory representations are held when they are ‘inactive’).
-But emphasis on stores does NOT mean that processes are ignored. - 3Continued-Memory systems include memory stores AND the processes that are involved when memory representations become active.
-“The idea of the opposition between ‘processes’ and ‘systems’ is a false belief. It probably came about because process-oriented students of memory have tended to line up under the banner of unitary memory…” (Tulving, 1999:12) - 4Cohen and Squire (1980): Declarative (explicit)-“knowing that”
-for example London is the capital of England, zebras are animals, your mums birthday etc.
-Recalling information from declarative memory involves some degree of conscious effort – information is consciously brought to mind and “declared”. - 5non-declarative (implicit)-“knowing how” to do things
-It included skills, such as “knowing how” to playing the piano, ride a bike; tie your shoes and other motor skills.
-It does not involve conscious thought (i.e. it’s unconscious - automatic). For example, we brush our teeth with little or no awareness of the skills involved. - 6Squire (2007): Recognition memory-Recognition memory is widely viewed as consisting of two components, recollection and familiarity, which have been proposed to be dependent on the hippocampus and the adjacent perirhinal cortex, respectively
- 7Schacter and Tulving (1994)-5 rather than 2
-One of the main points of disagreement between the two models is the episodic-semantic distinction.
-Because different systems are supposed to have different neural bases, a lot of evidence for them comes from the amnesic syndrome. - 8The amnesic syndrome-Main symptoms:
1. Anterograde amnesia: Severe impairment in the ability to learn new information (i.e. after the onset of the amnesia).
2. Retrograde amnesia: Some impairment in remembering information learnt prior (and close) to the onset.
3. Relatively intact working memory.
4. Some remaining learning ability.
- 9Clive Wearing-Herpes Simplex Encephalitis
-Lost the ability to form new memories
-Considerable semantic memory impairment
-Constant consciousness for 2-3 minutes
-His musical skills virtually intact
-Life is… “Hell on Earth – It’s like being dead – all the bloody time” (Baddeley, 1997:4) - 10H.M Henry Gustav Molaison-He suffered from epilepsy.
-At 27 (in 1953), he underwent surgery when most of his hippocampus was removed.
-His epilepsy came under control, but H.M. became severely amnesic (Scoville & Milner, 1957).
-He brought the hippocampus to our attention.
-Severe anterograde amnesia, some retrograde amnesia, intact STM, intact learning of perceptual and motor tasks. - 11The amnesic syndrome-Claparede (1911) – Pin concealed in palm
-Warrington & Weiskrantz (1970):
Groups of amnesics and non-amnesics
Amnesics performed substantially worse than non-amnesics at a recognition test.
-However, with implicit retrieval instructions, amnesics showed as much priming in word-stem and word-fragment tests as non-amnesics.
-i.e. They were more likely to complete the stems or fragments with previously seen words. - 12Focus: Episodic/Semantic distinction-What has the amnesic syndrome taught us?
-The episodic system is severely damaged and new memories cannot be formed.
-HOWEVER: amnesics maintain their intelligence, language skills and (largely) knowledge prior to onset. Therefore, the semantic system is largely intact.
-HOWEVER(x2): some studies indicate that amnesics cannot acquire new semantic (i.e. knowledge) memories either. (e.g. Cermak and O’Connor, 1983)
-Because both brain areas are damaged perhaps? We have no control over the extent of lesions in amnesic patients - 13KC-The case of KC (Tulving, 1985) who became amnesic after a motorcycle accident.
-Unlike HM, he can acquire new semantic memories, albeit slowly and with a lot of effort.
-Of course, KC cannot remember acquiring this new semantic information. - 14Vargha-khadem (1997)-Developmental or early onset amnesia:
-Vargha-Khadem et al. (1997) –
-Beth had bilateral hippocampal damage at birth and Jon from 4 yrs. Both had severe episodic memory impairment BUT both developed normally in all other respects (intelligence, language, knowledge etc). - 15Parkin-But what about an all important double dissociation?
-Parkin (2001:405) – “By definition an episode happens only once”.
-That is, perhaps semantic memories are easier to acquire because of the potential for repeated exposure.
-Semantic Dementia – e.g. Adlam et al. (2009)
-Yasuda et al. (1997): Patient with severe retrograde amnesia who could not remember public events, historical figures and some vocabulary prior to the onset.
-HOWEVER, she could remember personal experiences very well. - 16Further evidence: Cabeza and Nyberg (2000)-For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions.
-For episodic memory encoding, consistently activated regions included left prefrontal and medial temporal regions.
-For episodic memory retrieval, activation patterns included prefrontal, medial temporal, and posterior midline regions. - 17Further evidence: interdependence-However, what about the interdependency between the two systems?
-Semantic memory is always involved in the acquisition of new episodic memories.
-Nyberg et al. (2003) found that several brain areas were activated during both episodic and semantic tasks. - 18A critique of the systems approach: Criteria of defining-There is a lot of debate about the criteria to define a system.
-E.g. Roediger et al. (1999) demonstrated how recall and recognition tasks would qualify as memory systems! - 19A critique of the systems approach: Over-reliance on dissociations-Parkin (1999) – episodic retrieval involves right prefrontal activation while semantic retrieval involves left PFC.
-HOWEVER, this effect was found to be due to difficulty. If the tasks are equally difficult, the pattern is reversed - 20Tulving (1999:22)-“… there is no single representation of an originally encountered event anywhere in the brain. Different kinds of information about the event are ‘stored’ in different memory systems and sub-systems and used as needed.”
-That’s fine and it sounds reasonable. BUT how many systems are there? And how can we identify them?
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- Cog Exam Fichas sobre LTM: Systems, creado por Veton Vishka2 el 09/01/2019.
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- Veton Vishka2
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