Memory and its disorders Models of memory function Chris Moulin School of Psychology University of Leeds

Administration Slides are here:

Plan Types of Models Cognitive, box and arrow models Mathematical models Computational models Neural models Neuroimaging models Working Memory Procedural/Implicit/Non-declarative memory Autobiographical Memory Episodic and Semantic Memory

Types of Model Mathematical models Computational models Neural models Neuroimaging models Cognitive, box and arrow models

Mathematical Models Signal detection theory I spy in a signal detection paper: ROC curves d’ (D-Prime) Boring theories Hits, 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) A B Neuroscience Tests cognitive models

HERA Hemispheric Encoding/Retrieval Asymmetry Encoding – taking information in Retrieval – getting that information back For verbal materials: Left frontal lobe – encoding Right 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 Memory Episodic (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 days

Explicit Memory Ebbinghaus’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 learning e.g. old and new mobile phone functions and buttons PI - old learning interferes with current learning e.g. friend’s new girlfriend’s name

Tests of RI & PI Group Exp Cont Group Exp Cont Learn Cat-Tree - Learn Cat-Tree Learn Cat-Dirt Learn Cat-Dirt - Test Cat-Dirt Test Cat-Tree Cat Tree Proactive Retroactive

Modern Ideas The basics.

Phases of memory encodingretrievalstorage All three of these must be intact

Retrieval Explicit / Implicit retrieval Difference in awareness in retrieval Ecphoric / strategic retrieval(Moscovitch, 1992) Ecphoric retrieval: effortless retrieval on the base of a simple cue Strategic retrieval: effortful retrieval. Memory strategies required

Atkinson and Shiffrin’s model (1969) Sensory memory Short-term memory Long-term memory External input Large capacity storage Short time : 2s Small capacity Short time: 30s Enormous capacity Long 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

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 bufferPhonological 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 neuropsychology Semantic dementia Errorless learning