Memory III Working Memory & BrainAtkinson & Shiffrin (1968) Model of MemoryVisual Sensory StoreVisual Sensory MemoryIconic MemorySlide 6a memory test...Serial Position EffectsSlide 9Evaluating Modal Memory ModelBaddeley’s working memory modelPhonological Loop (a.k.a. articulatory loop)Reading rate determines serial recallWorking memory and Language DifferencesFeatures of the Phonological LoopSlide 16Storage and Rehearsal Processes in Phonological Loop are Functionally IndependentArticulatory SuppressionImmediate word recall as a function of modality of presentation (visual vs. auditory), presence vs. absence of articulatory suppression, and word length.Neural Network Models of MemoryNeural Network Models of MemoryLong-term memoryShort-term MemoryWorking Memory and Prefrontal CortexDelayed Match to Sample TasksSlide 26Slide 27Neural Network ModelRole of PFC in Memory EncodingMemory IIIWorking Memory & BrainAtkinson & Shiffrin (1968) Model of MemoryVisual Sensory Store•It appears that our visual system is able to hold a great deal of information but that if we do not attend to this information it will be rapidly lost.•Sperling (1960)–Presented array consisting of three rows of four letters–Subjects were cued to report part of or whole displayX M R JC N K PV F L BDemo at:http://www.dualtask.org/Visual Sensory MemoryDelay of cue (in seconds)Iconic memory  high capacity, rapid decayIconic Memory•Sperling’s experiments indicate the existence of a brief visual sensory memory – known as iconic memory or iconic store•Information decays rapidly (after a few hundred milliseconds) unless attention transfers items to short-term memory•Analogous auditory store: echoic storeAtkinson & Shiffrin (1968) Model of MemoryShort-term memory (STM) is a limited capacity store for information -- place to rehearse new information from sensory buffers Items need to be rehearsed in short-term memory before entering long-term memory (LTM)Probability of encoding in LTM directly related to time in STMa memory test...TABLECANDLEMAPLESUBWAYPENCILCOFFEETOWELSOFTBALLCURTAINPLAYERKITTENDOORKNOBFOLDERCONCRETERAILROADDOCTORSUNSHINELETTERTURKEYHAMMERSerial Position Effects•In free recall, more items are recalled from start of list (primacy effect) and end of the list (recency effect)•Distractor task (e.g. counting) after last item removes recency effectdistractor tasknodistractor taskSerial Position Effects•Explanation from Atkinson and Shiffrin (1968) model: –Early items can be rehearsed more often  more likely to be transferred to long-term memory–Last items of list are still in short-term memory (with no distractor task) they can be read out easily from short-term memoryEvaluating Modal Memory Model•Pro–provides good quantitative accounts of many findings•Contra –assumption that all information must go through STM is probably wrong–Model proposes one kind of STM but evidence suggests we have multiple kinds of STM storesBaddeley’s working memory model Baddeley proposed replacing unitary short-term store with working memory model with multiple components:Baddeley and Hitch (1974)Baddeley (1986)Allen BaddeleyPhonological Loop(a.k.a. articulatory loop)•Stores a limited number of sounds – number of words is limited by pronunciation time, not number of items•Experiment:•Word length effect – mean number of words recalled in order (list 1  4.2 words; list 2  2.8 words)LIST 1:BurmaGreeceTibetIcelandMaltaLaosLIST 2:Switzerland Nicaragua Afghanistan Venezuela PhilippinesMadagascarReading rate determines serial recall•Reading rate seems to determine recall performance•Phonological loop stores 1.5 - 2 seconds worth of wordsWorking memory and Language Differences•Different languages have different #syllables per digit•Therefore, recall for numbers should be different across languages•E.g. memory for English number sequences is better than Spanish or Arabic sequences(Naveh-Benjamin & Ayres, 1986)Features of the Phonological Loop•Phonological store–Auditory presentation of words has direct access–Visual presentation only has indirect access–affected by phonological similarity•Articulatory process –converts visually presented words into inner speech that can be stored in phonological store–affected by word lengthBy auditory rehearsal, a representation in the phonological store can be maintained17Storage and Rehearsal Processes in Phonological Loop are Functionally IndependentArticulatory Suppression•Saying “the” all the time leads to articulatory suppression•Disrupts phonological loop  worse performance•With visual presentation, articulatory suppression leads to bad performance but there is no word length effect visuospatial sketchpad takes overImmediate word recall as a function of modality of presentation (visual vs. auditory), presence vs. absence of articulatory suppression, and word length. Baddeley et al. (1975).Neural Network Models of MemoryNeural Network Models of Memory•Long-term memory:–weight-based memory; the memory representation takes its form in the strength or weight of neural connections•Short-term memory:–activity-based memory, in which information is retained as a temporary pattern of activity in specific neural populationsLong-term memory•Long-term associative memories can be formed by Hebbian learning: changes in synaptic weights between neurons –structural change–relatively permanentDonald O. Hebbco-activation strengthens weight between two unitsstrengthenede.g. thundere.g. lightningShort-term Memory•Change in neural activity not structural temporary•Reverberatory loop – circuits that maintain activity for a short period•DemoWorking Memory and Prefrontal Cortex•Correct response requires keeping location of food in mind.•Monkeys and humans w/lesions of PFC fail these tasks.Delayed Match to Sample TasksDelayed Saccade Task(Goldman-Rakic)Patricia Goldman-Rakic (1937-2003)Neural Network Model•Demo•Same demo (gif)Role of PFC in Memory Encoding-If fMRI activity at encoding is back-sorted according to whether words are subsequently remembered or forgotten, then lower left VLPFC (and hippocampus) activation predicts later forgettingLeft ventrolateral prefrontal cortexLeft parahippocampal