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1. The development of Baddeley's multiple component Working Memory model COGS 551: Human Memory
05. 03. 2007
2. 1. The Baddeley & Hitch WM model (1974): 3 components of WM Baddeley (2003:830)
3. 1. The Baddeley & Hitch WM model (1974): 3 components Baddeley (2003:830)
4. Second version: fractionating the VSSP and the phonological loop Visual cache
Passive short term storage of visual material Inner scribe
Encoding and active rehearsal of spatial sequences
6. Third version: The fractionation of the Central Executive The simplifying assumption of CE as a unitary attentional system has been given up in favour of a multiple CE:
Attentional control, i.e., focus, divide and switch attention
Connect WM with LTM, e.g., for chunking (allowing information in LTM to supplement immediate serial recall)
Allowing the slave systems to interact, in a separate WM component, distinguishable from LTM --> The Episodic buffer
7. A fourth component in WM The episodic buffer 'Limited capacity store that binds together information to form integrated episodes. It is assumed to be attentionally controlled by the executive and to be accessible to conscious awareness. Its multi-dimensional coding allows different systems to be integrated, and conscious awareness provides a convenient binding and retrieval process.' (Baddeley, 2003)
9. The relation between WM, sensory processing, and LTM The phonological loop, the VSSP, and the Episodic Buffer are
NOT extensions of LTM but separable storage systems of WM
NOT extensions of modality-specific processing of e.g., auditory and visual information
Episodic memory forms an intermediate multi-modal store in the service of the Central Executive
10. Functions of the Episodic Buffer Conscious awareness :
WM plays a role in consciousness
--> visual images, auditory-verbal imagery
--> phenomenological experience of remembering
Problem: where are the complex images stored?
How can information from various modalities be bound together into the representation of a coherent array of objects?
--> where and how does this binding take place?
By enabling the creation of new cognitive representations, the Episodic Buffer may facilitate problem solving
11. Functions of the Episodic Buffer Chunking and prose recall:
The phonological loop can hold up to 7+/-2 elements, e.g., words, in working memory
If aided by LTM, up to 16 units can be memorized
--> consciously chunked into a semantically coherent sentence, e.g., when instructed to combine these units to form a sentence
--> where and how is information from WM and LTM integrated?
12. Evidence for the Episodic Buffer Amnesic patients with good immediate prose recall There were two amnesic patients who had
Impaired LTM ('densely amnesic') but
Normal immediate memory for passages of prose of about 25 chunks ('idea units')
Normal capability of playing bridge
How could they have 'intermediate' memory (longer than WM) but have no LTM?
13. Functions of the Episodic Buffer Rehearsal:
In the phonological loop, subvocal rehearsal maintains phonological information
Subvocal rehearsal is a direct output process equivalent to vocalization
BUT: children also have some kind of rehearsal before they have the adult strategy of subvocal rehearsal
BUT: What about rehearsal in other modalities without a direct output process, e.g., in the VSSP
--> There is a more general process of rehearsal
It may involve sequential attention to the components to be remembered, either in the auditory or visual modality
--> Where does this general rehearsal take place?
14. Biological implementation of the Episodic Buffer 'Binding' of information through synchronous firing of nerve cells in nerve cell assemblies
No concrete anatomical location but involvement of the Prefrontal Cortex PFC (--> Central Executive)
Right frontal lobes involved in combining two separate tasks, verbal and visual (Prabhakaran et al. 2000)
15. References Baddeley, Alan D. (1996): The fractionation of working memory. Proc. Natl. Acad. Sci USA, 93, 13468-13472.
Baddeley, Alan (2000): The episodic buffer: a new component of working memory? Trends in Cognitive Sciences, 4, 417-432.
Baddeley, Alan (2003): Working memory: Looking back and looking forward. Nature Reviews Neuroscience, 4, 829-839.
Baddeley, A.D., & Hitch, G. (1974). Working memory. In G.H. Bower (Ed.), The psychology of learning and motivation: Advances in research and theory (Vol. 8, pp. 47--89). New York: Academic Press.
Prabhakaran, V. Et al. (2000): Integration of diverse information in working memory within the frontal lobe. Nat. Neurosci. 3, 85-90.