Working memory

WORKING MEMORY MODEL - BADDELEY, 2000

Central Executive - general system resembling attentional control (most important component)

Phonological loop - processing + brief storage of speech-based information

Visuo-spatial sketchpad - spatial and visual processing + brief storage

Episodic buffer - temporary storage for integrated information from phonological loop, visuo-spatial sketchpad and long-term memory

 

The Phonological loop

• keeps speech-based info for 1-2 seconds
• Articulatory Control Process
• translates visual info into speech-based info
• transfers this info to phonological store
• refreshes info in store to prevent decay

Word length effect

• short word recall > long word recall
• effect due to slower rehearsal of long words
• evidence shows articulatory suppression eliminates word length effect
• AS involves loop and hence causes disruption in word span task
• loop determined by temporal duration

Irrelevant speech effect - Salame and Baddeley (1982)

• Irrelevant speech effect -> recall declines
• Supports assumption that loop uses speech-based rehearsal processes
• Suggests if irrelevant material not speech-based, effect should disappear

The Visuo-Spatial Sketchpad

• temporary storage and manipulation of visual and spatial info
• Visual cache - stores info about visual form and colour
• Inner scribe - Deals with spatial and movement info
• Rehearses info in the cache
• Transfers info from the cache to central executive
• Spatial task = activation of right hemisphere
• visual task = activation of left hemisphere
• Most tasks use both components of the VSS
   

 

The Central Executive

• most important part of the working memory model
• supervises the 2 slave ssytems (loop +vss)
• function include
• Planning/organising 
• Inhibition
• Switching retrieval plans
• dual-task performance
• selective attention
• thought to be located in the frontal lobes

 

Summary

• There is a lot of evidence to support CE (random number generation, stroop effect, dual tasking)
• Contrasting evidence of CE location in the brain
• Lack of general storage component in the Model (loop +VSS process/store specific info only); CE = general processing

Episodic buffer

• Integrate info from range of sources (loop/VSS) into a single episode
• Hence acts as a buffer
• capacity of EB is about 4 chunks
• Episodic buffer should enhance memory when different kinds of information need to be integrated

Baddeley and Wilson (2002) study on EB:

• Compared amnesiacs with or without deficient CE
• Immediate prose recall was higher in those with efficient CE
• Supports need of normal CE for normal EB performance

However, they: 

• used the same group of amnesiacs
• Additional central executive task
• Same detriment on both groups
• Doesn't support need of normal CE of EB performance

 

WM model improved by the addition of EB:

• general storage facility was needed
• buffer between loop and VSS needed
• EB can store more info than the slave systems
• More research is needed to determine: how does info from loop and VSS combine to form 1 unit in EB?
• How does info from other sensory modalities (touch, smell) get stored in EB?

Conclusions

• Working Memory Model better than multi-store model as:
• can explain specific deficits in STM
• can explain impaired STM with normal LTM
• CE role not entirely understood
• More work needed to understand the EB, especially in patients
• Working memory deals with information on a short term basis