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Memory and its disorders Models of memory function Chris Moulin School of Psychology University of Leeds [email protected] 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 A B If this is true, then they should be in separate areas (but it is not disproved if they’re not) 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. MEMORY Declarative /Explicit Long Term Episodic (Autobiographical / past experience) Short Term and Working Memory Semantic (knowledge / facts) Procedural / Implicit Long-term memory systems Declarative memory (Explicit) Episodic memory Semantic memory Non Declarative memory (Implicit) Procedural memory 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: TRUMPET DIAMOND BANANA CHERRY SILVER MELON CLOUD Light & Singh, 1987 • • • • Mel ____ Sil_____ Tru ______ Clo____ Che_____ Dia ____ 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 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 Learn Cat-Tree Learn Cat-Dirt Test Cat-Dirt Cont - Cat-Dirt Cat-Dirt Group Exp Learn Cat-Tree Learn Cat-Dirt Test Cat-Tree Proactive Retroactive Cont Cat-Tree - Cat Tree Modern Ideas • The basics. Phases of memory encoding storage retrieval 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 Short term/Long term memory External input Sensory memory Large capacity storage Short time : 2s Short-term memory Small capacity Short time: 30s Long-term memory Enormous capacity Long time Atkinson and Shiffrin’s model (1969) Primary/Short-term • E.g. the recency effect – based on the phonological loop • Generally, Primary memory is not impaired by age young Recall (Prop. Correct) 1 0.9 old 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1 2 3 4 5 6 Serial Position 7 8 9 10 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 Working Memory Central executive Visuospatial sketchpad Episodic buffer Long-Term Memory Baddeley (1986, 1997) Phonological loop 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