Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
2/8/2017 Sensory Memory Working Memory, Cont’d • Iconic Memory (Visual) • Echoic Memory (Auditory) • These short sensory traces get maintained in memory – Short-term / Working Memory – Long-term Memory Information Theory Classic “Modal” Model of Memory • Claude Shannon (1916-2001) • Atkinson & Shiffrin (1965) – 3-store model of memory • “A Mathematical Theory of Communication” (1948) Photo: Alfred Eisenstaedt .1963. TimeLife “Coffee-house Internet passwords” What strategies did you use? • (In the old days, this might be phone numbers…) • Rehearsal – repeating item to yourself over and over • Chunking – re-coding the list into larger “chunks” • • • • • 4 characters: 6 characters: 8 characters: 10 characters: 15 characters: ST83 1M3MZ5 8RS4OFB9 M9TLUKDM2D SDXF5L2F36EH1M2 1 2/8/2017 Chunking Chunking • Try to remember the following string: • Get all that? 149162536496481100121 Chunking What strategies did you use? • How about if you divide it up into more meaningful chunks? • Rehearsal – repeating item to yourself over and over • Chunking – re-coding the list into larger “chunks” 1, 4, 9, 1 6, 2 5, 3 6, 4 9, 6 4, 8 1, 1 0 0, 1 2 1 12, 22, 32, 42, …, 112 • Potentially no limit to memory if chunked repeatedly • Also notice loss (not a strategy) — When you didn’t need the information anymore, you cleared your working memory 7±2 7±2 • George Miller’s landmark 1956 paper • How much information can human memory carry? • Uses Information Theory terminology: “bits of information” • Bits of information for simple tasks roughly the same regardless of modality – Think binary: 3.25 bits = 23.25 = 9.5… 2 2/8/2017 7±2 7 ± 2 Chunks • But! Words have more information in them than single letters… • How does this affect number of items in memory span? • It doesn’t • Can recode information into larger chunks • Number of chunks is always around 7 ± 2 A closer look… • Miller’s paper is foundational, but lacks complexity – Are all items in the list equal? – How does speed of information transfer affect memory? – How does memory change with task demands? Outline • Types of Memory – Sensory Memory • Memory Capacity • Memory Features • Working Memory (Much of the following material from the supplementary readings) • Excellent book from expert memory researcher Alan Baddeley • Over the years pushed & shaped our understanding of short-term / working memory Alan Baddeley (1934 – present) University of York img: https://en.wikipedia.org/wiki/Alan_Baddeley 3 2/8/2017 Serial Position effects Serial Position effects • Remember the 15 character password? • Which characters were easiest to remember? • Primacy – the first items are privileged • Recency – the most recent items are privileged Primacy & Recency hold over longer lists, too Explanation? • Modal Explanation – First items get rehearsed most – Items moved to LTM when buffer is full – Most recent items still stored in STM/WM What happens if we…? Serial effects – slowed presentation • Slow down presentation, to allow more time for rehearsal? • No effect on recency • Pre-recency items recalled better 4 2/8/2017 What happens if we…? Serial effects - Delayed recall • Slow down presentation, to allow more time for rehearsal? • WM decays over time… • Recency effects are removed – What if we delay recall? What happens if we…? Serial effects - Intervening Tasks • Slow down presentation, to allow more time for rehearsal? • WM decays over time… • Demo-• Try to remember the following items – What if we delay recall? • What about interfering with maintenance? Serial effects – Phonological Similarity Effect • List 1 – Contain? • Tan? • Cap? • List 2 – Contain? • Day? • Bug? • Now count back from 201 by 3 • Also blocks recency • • • • • • • • • • Wave Arm Ice Cat Middle Egg Blood Window Metal Garden Serial effects – Phonological Similarity Effect List 1: •Man •Can •Cap •Map •Pan •Tap •Cat List 2: •Pit •Leg •Day •Top •Cow •Pen •Hot 5 2/8/2017 Serial effects – Phonological Similarity Effect • Phonological Similarity leads to poor recall • Semantic similarity has a small effect Phon. Sim. Phon. Disim. Semantically similar Sem. Disim. Immediate Recall Vs. Learning… • In this experiment (Baddeley, 1966) – With longer lists (can’t fit all into memory) – If participants have to wait 20 minutes before recall… • Phonological Effects disappear • Semantic Effects (synonyms) get larger • Phon. Effect has to do with rehearsal Outline 2nd Reading • Types of Memory • Highly influential researcher in attention and short-term memory • Watch for him again in Attention lectures! – Sensory Memory • Memory Capacity • Memory Features • Working Memory Donald Broadbent (1926 – 1993) Applied Psychology Research Unit UK Medical Research Council Dates: https://en.wikipedia.org/wiki/Donald_Broadbent; img: http://www.mrc-cbu.cam.ac.uk/timeline/images/broadbent.jpg 6 2/8/2017 7 ± 2? 7 ± 2 chunks • Braodbent (1975) • There are some pretty good reasons to doubt that ~7 is the short-term capacity • Bits of information for simple tasks roughly the same regardless of modality • Let’s re-examine Miller’s evidence… 7 ± 2? Primacy & Recency hold over longer lists, too • Let’s re-examine Miller’s evidence… • And in the Recency effects… – Recall: recency is tied to keeping things in your rehearsal loop 7 ± 2? • Let’s re-examine Miller’s evidence… • And in the Recency effects… – Recall: recency is tied to keeping things in your rehearsal loop Q F X S R U V M L J D B 4! 7 2/8/2017 7±2? 7±2? • Broadbent also mentions: • Perfect Performance • On average, people can recall about 7 digits from a list • But how many can people almost always recall? • Broadbent also mentions: • Modal Performance • For lists of categorical items (foods, cities, etc.) most lists people come up with are 2-3 items long – About 3-4 7±2? 7±2? • • • • • Broadbent also mentions: • Running Memory • RM for manual gestures (not digits) seems to max out at about 3 Broadbent also mentions: Running Memory You hear a list of items When I pause, give me as many of the last items as you can recall • Last: 0 3 1 10 6 7 Pollack, I., Johnson, L. B., & Knaff, P. R. (1959). Running memory span. Journal of experimental Psychology, 57(3), 137-146. 7±2? Several different stages? • • • • • 7±2 comes from being able to perform some chunking of information • And from combining • When rehearsal is blocked, 3-5 items seems to be about the limit • May be limited by Attention Broadbent also mentions: Clustering If you monitor pauses in peoples’ recall They pause longest between clumps of ~3 items • Suggests we can only select ~3 items at a time, and then we chunk them • Will see more evidence in lectures on Attention! 8 2/8/2017 Several different stages? Primacy & Recency hold over longer lists, too • Broadbent suggests memory is divided into different “Stages” • (His exact formulation is a bit uncertain) • But let’s look at the serial position curves again: Serial effects - Delayed recall • Recency effects are removed 7±2? • Initial Items are pretty robust over time • These may be in Long-term memory • Last items are easily disrupted • These items are lost from an active, working memory store 7±2? Parts of the Working Memory System? • Separating these out, working memory appears to have a capacity of ~3-4 items • Baddeley & Hitch (1974) – Working Memory • 7±2 comes from chunking and use of longterm storage • • • • Auditory Visual (Episodic Memory) Central Executive – (Planning and setting goals) 9 2/8/2017 Phonological Buffer • Subvocalization • Can repeat things in Echoic Memory – up to a few seconds – Used in language – Sounds may be more time-dependent than images, since sound inherently unfolds over time Visuo-spatial Sketch Pad • Evidence: – Visualizable words are easier to learn • See also: Object-based Mnemonics – Spatial problem-solving aided by visual “working space” Episodic Memory • Combines elements into a single story or “episode” • Evidence: – People with Severe memory damage can still process individual sentences (sentences longer than Phonological Buffer) 10 2/8/2017 Central Executive Brain activation? • Coordinates behavior of the buffers • Keeps systems “on task” • Turns off subsystems after task is over • Curtis & D’Esposito (2003) • Dorsolateral Prefrontal Cortex (DLPFC) • Propose 4 major areas for working memory: – (P) Parietal areas • Evidence from people with frontal lobe damage • Some evidence from people with hippocampal damage • Stores information for location of objects – (F) Frontal Eye-Fields • Visuospatial buffer – (B) Broca’s Area • Phonological buffer – (D) DLPFC • Central Executive Clive Wearing BBC – Man Without a Memory Clip: https://www.youtube.com/watch?v=Vwigmktix2Y Deep Thoughts… Long-Term Memory (LTM) We are our memories. Without our memories, we are creatures of mere sensation. -d.r. 11 2/8/2017 Outline When people think of “memories”… • Types of long-term memory • Often think of specific things / events – Implicit / Explicit • How do we store? My first ride on a roller-coaster! Date of signing of US Constitution • What do we store? My best friend’s middle name • How durable is the store? My worst break-up Capitol of New York? Explicit Memory Semantic memory – not tied to specific time or place Date of signing of US Constitution My best friend’s middle name Capitol of New York? My favorite birthday party Memory is also Implicit Episodic memory – tied to specific events My first ride on a roller-coaster! My worst break-up My favorite birthday party • Processes / Procedural Memory – How to ride a bike • Classical / Operant Conditioning – Learned changes in behavior • Priming – Giving little bits of information to produce faster recognition Priming: example Priming: example • Dell’Acqua & Grainger (1999) • A masked stimulus is presented too fast for conscious identification • Decision task on word at end: • Is it a natural or man-made object? • Compare when Prime is semantically Related or Unrelated – A “Prime” Dell'Acqua, R., & Grainger, J. (1999). Unconscious semantic priming from pictures. Cognition, 73(1), B1-B15. Dell'Acqua, R., & Grainger, J. (1999). Unconscious semantic priming from pictures. Cognition, 73(1), B1-B15. 12 2/8/2017 Priming: example Memory is also Implicit • Responses are faster when primed with same category • Responses slower when primed with different category • Processes / Procedural Memory – How to ride a bike • Classical / Operant Conditioning – Learned changes in behavior No prime Semantically Related Semantically Unrelated • Priming – Giving little bits of information to produce faster recognition Dell'Acqua, R., & Grainger, J. (1999). Unconscious semantic priming from pictures. Cognition, 73(1), B1-B15. Implicit Memory Outline • Often a procedure • Does not require conscious recognition • Conscious thought may interfere • Types of long-term memory • Can measure changes in reaction / performance – Implicit / Explicit • How do we store? • What do we store? • How durable is the store? How are memories stored? How are memories stored? • Physical Location? • Synapse Strength? • Physical Location? • Lashley (1950) – Trained rats on various tasks – Then lesioned rat cortices in an attempt to find out where those behavioral memories were stored – Couldn’t find them in a single place 13 2/8/2017 How are memories stored? • Instead, errors in learning increased with amount of cortex lesioned • Physical Location? • Lashley (1950) – “It is not possible to demonstrate the isolated localization of a memory trace anywhere within the nervous system. Limited regions may be essential for learning or retention of a particular activity, but within such regions the parts are functionally equivalent. The engram is represented throughout the region.” (Definitions) How are memories stored? • Engram – The package of information that makes up a memory – the bound representation of experienced events, including: perceptual and conceptual fragments, • Physical Location? self-generated thoughts, contextual details, etc… • Trace – a pointer to the memory for retrieval • Lashley (1950) – “every instance of recall requires the activity of literally millions of neurons. The same neurons which retain the memory traces of one experience must also participate in countless other activities.” How are memories stored? Hebb 1949 • Physical Location? • Synapse Strength? • Classic work of cognitive neuroscience • Recall Hebbian Learning? – Cells that fire together wire together • Changing synaptic potential stores information • Lays out Hebb’s hypotheses on learning 14 2/8/2017 Classical Conditioning Physiology of Mind (Structuralism) • Wilhelm Wundt (1832-1920) Whtvr… • Sensation does not differ from ideation • “Blue is and remains blue” (whether sensed or imagined) Response is physiological and subconscious Image and dates: https://en.wikipedia.org/wiki/Wilhelm_Wundt Hebb 1949 Hebb 1949 • Each neuron has tons of connections • Cells fire in networks • Some cells will be linked in groups • These “assemblies” may “reverberate” Hebb 1949 • Even simple assemblies might reverberate for… half a second? • Reverb = short term memory? • Leads to continued firing / wiring = learning? However, in vivo… • We can try and record out of cells during a task • Do we see lasting reverb? Tania Pasternak, PhD University of Rochester Professor, Neurobiology & Anatomy, Brain & Cognitive Sciences, Center for Visual Science Bisley, J.W., Zaksas, D., Droll, J.A., & Pasternak, T. (2004). Activity of Neurons in Cortical Area MT During a Memory for Motion Task. Journal of Neurophysiology. Jan 2004, 91 (1) 286-300; DOI:10.1152/jn.00870.2003 15 2/8/2017 However, in vivo… • Record out of MT in awake monkey • Monkey sees motion sample • Delay • Monkey responds “same/different” to test stimulus Bisley, J.W., Zaksas, D., Droll, J.A., & Pasternak, T. (2004). Activity of Neurons in Cortical Area MT During a Memory for Motion Task. Journal of Neurophysiology. Jan 2004, 91 (1) 286-300; DOI:10.1152/jn.00870.2003 However, in vivo… • Activity drops off almost immediately • Poor evidence of local reverb Bisley, J.W., Zaksas, D., Droll, J.A., & Pasternak, T. (2004). Activity of Neurons in Cortical Area MT During a Memory for Motion Task. Journal of Neurophysiology. Jan 2004, 91 (1) 286-300; DOI:10.1152/jn.00870.2003 Complex interplay of areas? Distributed Neural Networks • Remember – • How could memory be so distributed? – Lashley: Memory is distributed – Lots of small changes add up? Distributed Neural Networks Distributed Neural Networks • Formed of multiple layers of “nodes” / neurons • Nodes/neurons in one level pass info onto nodes/neurons in the next level • Patterns of activation in level thus can cause a specific pattern of activation in the next group of nodes/neurons • Through learning and feedback, weights between nodes/neurons can change • This changes the information represented in the network • Online demos: http://www.mitchcrowe.com/visualizingneural-networks/ 16 2/8/2017 Example Distributed Neural Networks with Visual Distributed Neural Retinal Networks Areas • Example: handwritten letter detection Inferior • Example: handwritten letter detection Cones Rods & Ganglion Cells Temporal Areas Input V1, V2, etc… Conscious Recognition How are memories stored? How are memories stored? • Synapse Strength? Not everyone agrees • Gallistel & King (2009) Randy Gallistel • Gallistel & King (2009) • Memories are stored in cellular RNA/DNA • Caveat! – There is too little information at the synapses – How can functions and information possibly be maintained over the lifetime? – “We have no idea what the machinery might look like that would transcribe information from a spike train into a neucleotide sequence. How to gain access to the encoded number is also a mystery. We have no idea what the machinery might look like that would transcribe a neucleotide sequence into a spike train. But how it is that a neucleotide sequence could in principle encode a number is no mystery at all. Thus, such a proposal, wild as it is, passes the test that the synaptic plasticity hypothesis fails. And that is progress.” (p.280) Clinical Cases… • We’ll stick with the network approach for now… • Are there parts of the brain that knock out storage to LTM? 17 2/8/2017 Clive Wearing BBC – Man Without a Memory Clip: https://www.youtube.com/watch?v=Vwigmktix2Y Also, H.M. (Henry Molaison) • 1953, Doctors try experimental surgery to relieve seizures • Remove parts of Hippocampus & Temporal lobe (function then unknown) • Post surgery, H.M. could no longer form new memories E.P. PBS - American Scientific Frontiers (2004) https://www.youtube.com/watch?v=7Grh3PeEMIg 3:10 – 11:16 H.M.’s brain online • http://hm.brainandsociety.org/hm _web/ Lesion Cellularlevel resolution All suffered damage to Hippocampus • Hippocampus is part of the limbic system • Located in the medial temporal lobe • Essential to moving information from WM to LTM 18 2/8/2017 Role of Hippocampus? Role of Hippocampus? • How does hippocampus get info from WM to LTM? • Unclear. • But, consider: • Also note: These were formation of explicit memories • What about implicit memories? – Hippocampus reactivates recent experiences during “off-line” periods (rest & sleep) (Sutherland & MacNaughton, 2000; Davidson, et al, 2009) (Will discuss more in consciousness lecture) HM – Mirror Drawing Role of Hippocampus? • Also note: These were formation of explicit memories • What about implicit memories? – Implicit memories may rely on other areas 19