LTM Structure Part 1.pdf

 This presentation contains images owned by third-parties. They can be used for educational purposes in this presentation. The following copyright warning must be provided prior to presenting them: Copyright Warning This material has been copied and co...

 This presentation contains images owned by third-parties. They can be used for educational purposes in this presentation. The following copyright warning must be provided prior to presenting them: Copyright Warning This material has been copied and communicated under the Statutory Licence pursuant to s113P of the Copyright Act 1968 for the educational purposes of the University of Adelaide. Any further copying or communication of this material by you may be the subject of copyright protection.  Part 1 (Lecture 1) Part 2 (Lecture 2) What is Long-Term Memory? Episodic and Semantic Memory Short-Term vs. Long-Term Memory Episodic Memory and Future Imagining Are STM and LTM Separate Systems? Procedural Memory and Priming Long-Term Memory Coding Squire’s (1992) Model of LTM Recommended Reading There are two long-term memory chapters in Goldstein (2018). This week, focus on: Goldstein Chapter 6 Long-Term Memory: Structure I discuss most major topics* but don’t always cover them in the same order. I also cover interesting topics that are not in the chapter What is Long-Term Memory? A relatively permanent storage vault for a lifetime’s worth of knowledge and experience (Ashcraft & Radvansky, 2013, p. 209) We use it to remember: 1. General knowledge (semantic memories): Includes facts, meanings, and concepts 2. Events from our lives (episodic memories): Includes what/when/where and how we felt 3. Skills (procedural memories): Includes tying our shoelaces, driving, and writing our name Distinguishing STM and LTM STM: A store that holds in mind, in an active, highly available state, a small amount of information LTM: A relatively permanent storage vault for a lifetime’s worth of knowledge and experience If you are currently (or very recently) thinking about something, it is in STM. If not, but is accessible later, it is in LTM STM and LTM Continually Interact STM and LTM continually interact. For example:  STM sends information to LTM for storage  STM accesses info stored in LTM (see right)  LTM can increase STM’s capacity by combining single pieces of info into meaningful chunks*  Demonstration Instructions You will now complete a quick memory test demonstrating the serial-position effect The test demonstrates how information passes between STM and LTM I will read out 15 words and give you 1 minute to recall them Find something to write/type on when recalling the words Are you ready?  Demonstration Results You can see the 15 words below. Of the words you correctly recalled:  How many came from the start of the list (i.e., the first 5 words)?  How many came from the middle of the list (i.e., the middle 5 words)?  How many came from end of the list (i.e., the last 5 words)? You should recall more from the start and end than the middle. Why? This is discussed next Barricade, Phoenix, Meteor, Children, Crossbow, Journey, Diet, Alligator, Mohair, Guard, Doorbell, Menu, Polio, Muffler, Archer The Serial-Position Effect Murdoch (1962) tested recall of word lists that had varying lengths (10 - 40 words). He found:  A Primacy Effect: More start-of-list words recalled than middle-of-list words  A Recency Effect: More end-of-list words recalled than middle-of-list words Why does these effects occur?  The Serial-Position Effect Why does the Primacy Effect occur? Blue dashed line = Number of times words rehearsed Rundus (1971) argued early list words are rehearsed most/enter LTM for durable storage To test this, he had participants vocalise their rehearsal when studying the lists. Early words were rehearsed more than middle-list words/recalled better than middle-list words When you studied the word list during my demonstration, did you rehearse the early words more than middle-list words?  The Serial-Position Effect Why does the Recency Effect occur? Glanzer & Cunitz (1966) argued late-list words are still in STM and are easily recalled To test this, they gave half their participants a 30 sec delay after studying the lists, so the words left STM. The recency effect disappeared When you recalled the word list during my demonstration, were the most recent list words still alive in your mind/in STM? The Serial-Position Effect End of list words still in STM during recall Overall, serial-position effect studies show: Early list words entered LTM for durable storage 1. Information we have rehearsed is stored in durable LTM traces/is recalled reasonably well 2. Information we have recently seen is still in STM so is easily recalled 3. Information we have not had time to rehearse (and is no longer in STM) is less well recalled Are STM and LTM Separate Systems? A minority of theories argue the separation between STM and LTM is misguided and that STM is simply a part of LTM that is activated at any given moment (e.g., Cowan, 1999) One problem with this alternative theory is that amnesic patients can show a double-dissociation between STM and LTM. Goldstein (2018) gives one example (below): Are STM and LTM Separate Systems? Patient K.C. had a motorcycle accident aged 30 and suffered brain lesions. His Verbal STM worked but aspects of his LTM were damaged (more on this later) In class, we will watch a 2 min video of K.C. K.C.’s real name was Kent Cochrane. receiving STM and LTM tests from Endel Tulving He died in 2014, aged 62  STM and LTM in the Brain STM and LTM involve several separate brain areas. You can see some on the right (e.g., Prefrontal Cortex = Central Executive) In that same image, the hippocampus is listed as being associated with LTM. There is a debate over whether it is also involved in STM processing. That debate is discussed next See Chai et al. (2018) for a more detailed map of the multiple brain areas associated with different Working Memory systems The Hippocampus and LTM Traditionally, we believed the hippocampus creates LTM’s/is not involved in STM This belief was based on evidence from brain lesions patients like H.M (Henry Molaison) In 1953, surgeons removed his hippocampi to control epileptic seizures. Post-surgery, his STM was normal, but he was unable to form new LTM’s  H.M.’s Brain Patient H.M. and part of his brain at the Science Museum in London, You can study his brain here: https://www.thebrainobservatory.org/project-hm/ The Hippocampi and STM Maintenance? Later Cognitive Neuroscience research suggests the hippocampus may assist with STM maintenance (keeping information alive in STM). Nichols et al. (2006) had participants study faces for 2 secs, hold them in STM for 7 sec, and tested their memory of the faces immediately (STM) and after a 15 min delay (LTM). They found hippocampus activation when faces were held in STM and during the LTM task STM Task LTM Task Hippocampus Activation The Hippocampi and STM Maintenance? Whether or not the hippocampus is involved in STM maintenance (or other STM processing) likely depends on what is being remembered  Example 1: Ni et al. (2019) examine brain activity via fMRI during STM and LTM tasks involving numbers. There was no hippocampus activity during the STM task  Example 2: Hartley et al. (2007) found patients with hippocampus damage had impaired STM of landscape images (e.g., images of hills, with clouds in the background) More research needed to identify the role of the hippocampus in STM processing What is Coding? Different external stimuli (visual stimuli, sounds, etc) is stored in LTM in different formats/codes (more on this next). The process of storing external stimuli in LTM is called encoding (Goldstein calls it coding) When information that is stored in LTM is needed, it is retrieved/recollected and returned to STM. It is then represented in our minds in the format/code it was stored in Types of Encoding/Coding There are many types of coding, including: 1. Visual coding: Visual stimuli are coded and represented in LTM as visual images (e.g., you can mentally picture a friend’s face) 2. Auditory coding: Sounds are coded and represented in LTM as sound-based images (e.g., you can mentally hear a song you heard)  Semantic Encoding/Coding Semantic coding is a type of coding in which the general meaning (i.e., the gist) of a sentence, story, or event is coded and stored in LTM* When recalling the information, the semantic representation (the gist) appears in our minds Next, I will ask you take part in a demonstration modelled on Sachs (1967) that shows this Semantic coding occurs as we cannot store every single detail of every single sentence, story, or event we encounter in LTM  Demonstration Instructions I will read out a short story After that, I will ask you to complete a couple of brief tasks  The Story There is an interesting story about the telescope. In Holland, a man named Lippershey was an eye glassmaker. One day his children were playing with some lenses. They discovered that things seemed very close if two lenses were held about a foot apart. Lippershey began experimenting and his "spyglass“ attracted much attention. He sent a letter about it to Galileo, the great Italian scientist. Galileo at once realized the importance of the discovery and set about to build an instrument of his own. He used an old organ pipe with one lens curved out and the other in. On the first clear night he pointed the glass toward the sky. He was amazed to find the empty dark spaces filled with brightly gleaming stars! Night after night Galileo climbed to a high tower, sweeping the sky with his telescope. One night he saw Jupiter, and to his great surprise discovered near it three bright stars, two to the east and one to the west. On the next night, however, all were to the west. A few nights later there were four little stars.  Demonstration Instructions Now spend 30 seconds answering the following simple maths questions What is 7 + 8? What is 5 x 6? What is 12 / 3? What is 23 – 8? These questions included to try and ensure the story exits your STM  A Question Which of the following sentences is identical to one the story you heard? a) Galileo, the great Italian scientist, sent him a letter about it b) He sent Galileo, the great Italian scientist, a letter about it c) He sent a letter about it to Galileo, the great Italian scientist d) A letter about it was sent to Galileo, the great Italian scientist People struggle working out whether (b), (c), or (d) is correct. Is that true for you? The answer is (c) Semantic Encoding/Coding Sachs (1967) found participants easily recognised (a) was wrong:  It is inconsistent with the gist of the story/did not match the semantic representation in LTM Some participants struggled telling whether (b), (c), or (d) were identical to the original:  All are consistent with the gist of the story/matched participants’ semantic representation of it To easily identify which sentence was identical to the original, participants would have had to create an exact representation of it in LTM. That does not happen as it would take up too much memory Multiple Representations We can code multiple aspects of a stimuli and hold multiple representations of it in LTM. Think of a movie you saw years ago, like Frozen:  You recall the plot as semantic coding stored a semantic representation in LTM  You can picture the characters as visual coding Can you remember the movie plot and stored visual representations of them in LTM visualise the Olaf character? Atkinson and Shiffrin’s (1968) Modal Model of Memory Atkinson and Shiffrin (1968) proposed the first major model describing human memory’s structure They suggested we have three major memory systems: Subsequent research showed LTM has several subsystems, and these are discussed in this lecture Squire’s Model of LTM (1992) Squire (1992) proposed the first major model of LTM. It is still the main model today. He said we have two qualitatively different categories of LTM and, combined, they have 6 systems: Category Systems Distinguishing Feature Declarative Memory 1. Episodic Memory (events) These memories appear in consciousness (aka Explicit Memory) 2. Semantic Memory (facts) (our thoughts) when accessed (e.g., we think about an event or fact) Nondeclarative Memory 3. Procedural Memory (skills) They influence behaviour without any (aka Implicit Memory) 4. Priming (discussed later) conscious recollection (e.g., recalling how 5. Classical Conditioning to tie your shoelaces) 6. Habituation  The Biological Bases of Squire’s Model of LTM (1992) The medial temporal lobe includes the hippocampus Squire’s Model of LTM (1992) Tomorrow, I will discuss four components of Squire’s Model of LTM (1992) in detail: 1. Episodic Memory (events) 2. Semantic Memory (facts) 3. Procedural Memory (skills) 4. Priming (discussed next week, as very diverse) These four components feature in all major models (some models have fewer / more systems) By the end of Long-Term Memory Structure: Part 1, you should be able to: 1. Explain how STM and LTM differ at a functional level 2. Explain whether or not STM and LTM are biologically distinct 3. Explain how information is encoded/coded in LTM and what semantic coding is 4. Explain how declarative and nondeclarative memory differ 5. Name the different declarative and nondeclarative memory systems in Squire’s (1992) LTM model