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
