memory and its disorders models of memory function chris moulin school of psychology university of...
TRANSCRIPT
Memory and its disorders Models of memory function
Chris Moulin School of PsychologyUniversity of Leeds
Administration
• Slides are here:
Plan
Types of ModelsCognitive, box and arrow modelsMathematical modelsComputational modelsNeural modelsNeuroimaging models
• Working Memory• Procedural/Implicit/Non-declarative memory• Autobiographical Memory• Episodic and Semantic Memory
Types of Model
Mathematical modelsComputational modelsNeural modelsNeuroimaging modelsCognitive, box and arrow models
Mathematical Models
• Signal detection theoryI spy in a signal detection paper:
ROC curvesd’ (D-Prime)Boring theoriesHits, misses, correct rejections and false
positives
• Powerful Model for recognition memory
Theoretical Assumptions
• Trace strength model based on normal distribution
• There is signal and there is noise
Recollection in Rats
Computational Models
• E.g. Connectionism• A way of modelling the brain?• You can train these networks to do things
Neural Models
• E.g. Long Term Potentiation
LTP
• Brain made up of billions of neurons, which are connected by synapses.
more LTP
• Repeated activity of the neuron causes synapses to become potentiated - meaning they fire easier.
• Networks of neurons can be activated when only one neuron in that group is stimulated.
even more LTP
• Further research found that after continued activity of neurons new synapses are grown to connect to other neurons.
• So networks of neurons can become massive e.g. one neuron can be connected to as many as 1000 other neurons.
• Associations in LTP are similar to associations in classical conditioning.
Neuroimaging Models
• E.g HERA.
Converging Evidence
Cognitive theory says that there is ability A and ability B and they are separate
If this is true, then they should be in separate areas (but it is not disproved if they’re not)
AB
Neuroscience Tests cognitive models
HERA
• Hemispheric Encoding/Retrieval AsymmetryEncoding – taking information inRetrieval – getting that information back
• For verbal materials:Left frontal lobe – encodingRight frontal lobe – retrieval
Encoding
controls
Retrieval
controls
HERA – so what?
• HERA not generally supported by patient studies.
• Left sided activation is prevalent for any verbal material that is later remembered
• Largely PET-based and doesn’t extend to fMRI
• Does it help us understand memory and memory problems?E.g. Aging
Box and Arrow models
•The majority of memory models are this•But converging models are the most powerful
Memory Refresher
• Memory is not a monolithic entity.
Long Term Short Term and Working MemoryEpisodic
(Autobiographical / past
experience)
Semantic (knowledge /
facts)
Declarative/Explicit
Procedural / Implicit
MEMORY
Declarative memory(Explicit)
Non Declarative memory(Implicit)
Episodic memory
Semantic memory
Procedural memory
Long-term memory systems
Procedural/Implicit
• Well learned skills tend not to decay too much• Cognitive measure: Priming• Laver & Burke (1993) Meta analysis: if
anything, older adults show more priming.• Light & Singh (1987). Nice memory test:
TRUMPETSILVERDIAMONDMELONCHERRYCLOUDBANANA
Light & Singh, 1987
• Tested either with implicit stem completion or explicit• Only difference is instruction• Old = Young on implicit• Old impaired when instructed to use a word they’d
previously seen
Mel ____ Sil_____
Tru ______ Clo____
Che_____ Dia ____
Explicit Memory
The early daysThe early days
Explicit Memory
Ebbinghaus’s forgetting curveEbbinghaus’s forgetting curve
Reasons for forgetting
• decay of memory trace• retrieval problems - not lost but misplaced • interference between memory traces
• Interference is important in Stimulus-Response
• E.g. Hugo Munsterberg
Retroactive & proactive interference
• Interference - cornerstone of behaviourist approach to human verbal learning
• RI - new learning interferes with recall of old learninge.g. old and new mobile phone functions and buttons
• PI - old learning interferes with current learninge.g. friend’s new girlfriend’s name
Tests of RI & PI
GroupExp
Cont
GroupExp
Cont
LearnCat-Tree
-
LearnCat-Tree
Cat-Tree
LearnCat-Dirt
Cat-Dirt
LearnCat-Dirt
-
TestCat-Dirt
Cat-Dirt
TestCat-Tree
Cat Tree
Proactive
Retroactive
Modern Ideas
• The basics.
Phases of memory
encoding
retrievalstorageAll three of these must be intact
Retrieval
• Explicit / Implicit retrievalDifference in awareness in retrieval
• Ecphoric / strategic retrieval (Moscovitch, 1992)Ecphoric retrieval: effortless retrieval on the base of a simple cueStrategic retrieval: effortful retrieval. Memory strategies required
Atkinson and Shiffrin’s model (1969)
Sensory memory
Short-term memory
Long-term memory
External input
Large capacity storageShort time : 2s
Small capacityShort time: 30s
Enormous capacityLong time
Short term/Long term memory
Primary/Short-term
• E.g. the recency effect – based on the phonological loop
• Generally, Primary memory is not impaired by age
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 2 3 4 5 6 7 8 9 10
Serial Position
Recall (Prop. Correct)
young
old
Working Memory
• A new model : Baddeley and Hitch (1974)
'Perhaps short-term memory had no function other than to keep experimental psychologist amused ? it that were so, we would rather amuse ourselves in other ways' Baddeley
Working memory
• Think of working memory as short-term memory with some clever stuff added.
• Simultaneous storage and manipulation
central executive
phonological loop
visuospatial sketchpad
Central executive
Visuospatial sketchpad
Episodic buffer Phonological loop
Long-Term Memory
Working Memory
Baddeley (1986, 1997)
Some critical themes
• Verbal Learning Approach - Interference• Memory as process - Levels of processing• Technology affects models• Neuropsychology tests models• Lack of congruity between models
• But models guide neuropsychologySemantic dementiaErrorless learning