okay this chapter is about working memory and cognitive control the last chapter was about longer-term forms of memory I did talk about working memory mentioned it a few times and now we're gonna dig into a little bit it's basically just a system where you hold information for shorter periods of time and it turns out it's also a little more than that because you can't really talk about passive storage in a currently activated focus of attention currently thinking about it kind of way because that's an active process sort of by definition so it's working memory refers to the fact that it's really more than just a storage system but a system for storing and manipulating information and controlling what information is in it and thus it becomes really more very central to what that conscious mind is and does so it's more really than just a memory system as if it's possible that makes any sense to say just a memory system considering how central memory is to cognition as usual we'll talk about some theoretical get a good theoretical understanding of stuff and then moving to the brain substrates and a couple of clinical perspectives so the short-term memory as just refers to you know shorter term memory and like I said you might think of this as being you know what you learned five minutes ago is still in short-term memory but actually short-term memory the system is more like seconds 20 30 seconds something like that once you get much beyond that and take your mind off things they start to depend on longer term memory mechanisms in the brain in order to stick there we need to see some you know changes in the strength of synapses or something like that rather than just patterns of activity that are maintained and recursive loops so short-term memory is pretty refers to pretty short-term however this is an empirical question meaning we can answer this by doing studies experiments look at the data let that tell us what the duration of short-term memory is we can also ask what is the capacity of short-term memory so and you can ask this for any memory system how much can it hold what's its capacity and how long can it hold it for what's its duration classic example of holding something in short-term memory is if I give you a phone number you rehearse it over and over in your head that's you holding it in short-term memory until you dial it and then you're good maybe while you're dialing it you kind of stop rehearsing it but it's still accessible you still got it it's in short-term memory all right so let's do a little demonstration here virtually see if we can figure out how much you can hold in short-term memory ready I'm gonna read off some letters and you just try to remember as many as you can in the correct order W P I D F and I u q a H F all right write down as many as you can remember maybe pause it and then write down as many as you could remember because I'm about to show you it's not um so typically people get in tests like this about seven letters maybe six five sometimes eight about seven in fact there was a paper published a long time ago influential one called seven plus or minus two the magic number because surprisingly researchers are actually able to put a pretty pretty close I mean you know obviously not exactly seven but even the fact that you can come close you're describing a human memory system as having a capacity of seven things or seven slots is a little surprising that such an organic system would have such a quantifiable capacity of course there are many factors that affect how many things you can hold in this system let's try it again here's another set of letters ready f.b.eye [Music] c.i.a k g b i-r-s all right write down all the letters you can remember and pause it and then write down all the letters you can remember I should have said positive okay unpause now I'll show you what you had there but some of you probably got all because why it's the same number of letters however it turns out you can't it's not that you're working or short-term memory can remember seven letters we can remember a lot more than seven letters let's say I gave you seven words dog truck eggplant farmhouse everybody can remember those and there's seven letters in one of those words you add up all the letters it's a lot more than some so obviously how you organize the information makes a big difference with regard to how much information you can hold this phenomenon or a large part of it is known as chunking right so maybe some of you noticed those second list of letters I gave you consisted of three letter acronyms for FBI CIA KGB which is like the Russian FBI secret police that used to exist and now is probably back and the IRS so for WPI bf NIU those each letter kind of was on its own and took up one spot in a slot they call them slots in working memory but FBI is not three things it's one thing it's the FBI that takes up one slot CIA again one thing not three takes up one slot basically why are we able to remember more letters when we can group them because we can compress information instead of having FBI be three unrelated things we can make a tag to one thing that already exists in long-term memory and it takes up one spot in our working memory system so a critical thing to notice here is that in order to do that you have to have pre-existing knowledge in long-term memory you wouldn't be able to chunk F and B and I together if you never heard of the FBI if it was some Chinese agency you'd never heard of you wouldn't be able to chunk it so this is another example of what is in long-term memory general knowledge information semantic knowledge memory influencing the capacity and general ability for other memory short-term memory systems to function I guess what I'm saying is you can remember more in short-term memory the more long-term knowledge you have built up because you can use that non long-term knowledge to organize and scaffold your memory representations and this chunking is one example all right however the capacity of short-term memory it's not seven letters it's about seven chunks seven things it varies a little bit of course one's ability to chunk depends on what one knows some people can chalk better than others but everybody does it of course and the size of the chunks matter generally you can remember more things more chunks if they're on the smaller side for example if words that have more syllables you can hold fewer of them and we'll get to why this would be later but you may be able to guess that it has to do with the fact that we hold words in general in short-term memory in a sound based format it's like we say them in our heads and it takes longer to say longer words so we can't hold as many of them on our limited little tape loop that we hold things on at least sound based things will come back to that full article up idea shortly point here is that bigger chunks are generally harder to hold but still about seven chunks of course another important factor is particularly when we get to questions of how long can you hold stuff in this system for is rehearsal right so you can hold a lot more for a lot longer if you are allowed to sit there and just rehearse it that is refresh it so for verbal information like this if you can just sit there and go whi P and D bla bla bla bla bla bla bla whi D and repeat it over and over you can hold a lot more for obviously a lot longer if you sat there and did it forever rehearsed it forever you could hold it for the rest of your life in short-term memory but a more telling test would be to see how long can you hold stuff in this short-term memory system for if you're not allowed to rehearse it and so there are various tests that are you is to check this for example right after I give you the letters I want you to remember you have to immediately start counting backwards by threes from the number I give you all right so I'm going to give you four letters and then I'm gonna give you a number and we cannot rehearse the letters that's the whole point I mean you can but you'd be cheating instead you need to immediately start counting out loud backwards by threes so because when I do this in class they give a number and everybody just stares at me like a broken Chucky doll let's practice a little bit here if I sent thirty five you'd go thirty two twenty nine twenty six twenty three twenty seventeen fourteen that's counting backwards by threes you don't have to do with that fast the point is you need to take your mind off of the letters I gave you and we'll see how long they can stick D and K p17 go all right what were the letters I don't care the point is that's how you prohibit or suppress rehearsal and when you do that you find data something like this this is based on an old study but people got three letters to remember but then again we're not allowed to rehearse them at all they heard him once that was it and because right away they had to start counting backwards by threes which is kind of takes up your you know you have to pay attention to do that it's not that easy a task and what they found was that after counting backwards by threes for three seconds people remembered pretty much all the letters all the time almost a hundred percent accuracy but you'll see that as that retention interval goes up three six and three seconds six seconds nine seconds 12 seconds looking at that bottom x-axis on the graph there by the time you get to 15 18 seconds of counting backwards by threes okay without having ever been able to refresh or think about those letters again people forgot almost all of them all the time so this tells you probably a more accurate picture of the time scale of or the duration of these of this short-term or working memory system if you're not allowed to refresh it you know he just lighted up once and then see how long it sticks not that long you know 20 seconds something like that and you know this isn't there's no exact number but this gives you an idea that it's not like five or ten minutes it's more on the order of seconds and of course this is a forgetting curve we've got amount recalled on the vertical y-axis and then retention interval on the x-axis alright so why does stuff go away from short-term memory well first of all just to recap what's the capacity short term working memory about seven chunks what's the duration you know 20 seconds give or take of course it depends on the size of the chunks the ability to rehearse all that stuff but anyway you remember decay are old buddies decay and interference from our discussion of episodic and semantic longer term memory the same mechanisms apply for losing information from short-term memory again decay pretty much just means stuff goes away due to the passage of time and interference on the other hand says well maybe but stuff goes away because new stuff comes in and messes it up or old stuff that was already there is interfering and messing it up that's the idea of interference and you'll probably remember proactive and retroactive interference did we talk about this in the last chapter I don't remember but we'll talk about it now clearly basically Pro oh yeah we did talk about this proactive is when and remember that it's the direction that the messy up signal goes in if the messy up signal is going from something older forward in time and messing up something newer that's proactive stuff from before messes up stuff from later or stuff from now retroactively is when stuff from later in time or for right now is going backwards retro in time and interfering with stuff from earlier that you memorized before all right so both of these mechanisms of loss of information from memory are at play in short-term systems just as they are in long-term systems and there's been a bunch of studies and generally interference is very easy to show it shows up all the time it's definitely a reliable way to screw up memory and it's demonstrated by paradigms where for example like I said if you learn you know for lists of words if they're all fruits they interfere with each other more and you don't do as well on a memory test if you learn for list of words and ones fruits ones cars ones jobs and one is animals those don't interfere with each other as much and so memories not as bad decay actually sometimes decay doesn't show up so it's generally accepted that yes merely the passage of time causes memory to go away but it's also really hard to separate that from interference because usually when time passes interference is going to happen and in some paradigms for example if you learn a list of words it's called list a and then you wait five minutes and learn list B and then you're immediately tested on list B write list a should decay during those five minutes and thus not interfere with list B as much let's say they're both lists of fruits so they have a tendency to interfere with each other you should see less interference there than if you learn a and then right away learn less B and then right away or test it on list be a should interfere less in that condition I'm sorry they should interfere more in that condition because it hasn't decayed as much if you learn list a and then wait 5 minutes list a should be decaying that whole time and thus it should interfere less with list B but this is not what we find people have tried to find that lists that are older have decayed more and thus interfere or less and for some reason that doesn't seem to be the case so this isn't to say that decay is not a real thing it's just to say that interference is probably the main mechanism by which information is lost from short-term memory it's much more robust and generally observed than decay which is a little trickier to find evidence for all right so there's a basic introduction to some basic short-term working memory concepts in order to fit this next model of memory systems we're going to talk about into what we've talked about so far here is a breakdown of some of the distinctions that were made in the previous set of slides between different memory systems of course we focused on those longer term mostly those declarative episodic and semantic systems talked about implicit memory as well but now we're talking about this first box working memory right and it turns out that and disk consolidation is too showing that that's the process that has to happen for information to be transferred from this working or short-term memory system into the longer-term systems I mean it turns out an even shorter term memory system called sensory memory has been hypothesized to exist even before you might say the working memory or short term store this is a very influential memory model the Atkinson shipper model sometimes called this process model doesn't really matter I will I may refer to it but I'll be very clear about what I'm talking about this basically this middle box the short-term store and the long-term store the right-hand box those are the same two systems the long-term store includes implicit and explicit semantic and episodic that's all parts of long-term memory and the short-term store is what we just talked about hold about seven things the capacity I mean duration less than a minute but this model also has this new thing we haven't seen yet which is the sensory store which is over here on the left so this is a fairly old model it has some problems but it also has some true things in it make some important distinctions that there's a lot of evidence for but let's talk about this well in this new store here the sensory store in context the model basically suggests information comes in from the outside world right that's environmental input over on the left it goes in and the first store it enters is the sensory store which is like kind of a sensory echo or after image if you will of stuff that goes in your sensory holes so you have a separate sensory store for visual auditory haptic all these different types of information and and accordingly visual the visual sensory store is in the visual cortex the auditory sensory store is in the primary auditory cortex it's kind of like if I say but going that kind of rattles around in your ear exactly as it sounded for a few seconds but will soon be gone that's kind of your auditory sensory store another example of this sensory store sometimes called the sensory register is if you're like I don't know watching a movie that you're really into and focused on but someone is trying to talk to you at the same time and you're like uh-huh uh-huh but you're not really listening you're not paying attention to what they're saying you're not bringing what they say into your conscious workspace that is your short-term or working memory and processing it but it's still going in your earholes if they say are you even listening me you might be able to really quickly turn your attention from the movie to what's rattling around in your auditory sensory store while it's still there pull it into your conscious mind and say yeah you want me to empty the kitty litter I got it but if you wait just like five seconds it'll be gone from the auditory sensory store and never to be retrieved so the idea is everything that goes in your that you sense goes into your sensory store but the truth is you really only pay attention to or notice a fraction of that information when you do attend to something that's when it goes from the sensory store into your short-term store or your working memory so how much can the sensory store hold and what is the duration for it probably as you can guess it's pretty short if it's because there's a lot of interference messing with that stuff and if you don't pay attention to an ex-con immediately but let's watch here see if we can do a test of the okay remember all the letters you can I should have told you this before I put it up but there it is and in the lab typically people would I'd say ready and then you'd flash up a grid of letters probably not for that long and then say okay write down all the letters you can and if you try to test this is a measure of the sensory store right because you're kind of reading the letters out of that visual after image which is kind of like the sensory store people get about four which might make you say oh the sensory store can only hold about four things maybe five but Sperling used a clever partial report technique wherein right after the grid of letters shows up the participant here's a tone that's either high which means report the top row medium B report the middle row or low o the point at the bottom row right after it goes away and when you use this partial report technique if you do it right you can get people to recall accurately any of the four rows three row any of the three rows all four letters in any row which proves they're all in there to start with the problem is if you don't use the partial report technique people you know look at the after image of the grid of letters in their minds eye and they start reading out and they get the top row by the time they get to the second row it's already faded away so the point of this partial report technique is that it's all accessible so the capacity of this sensory store is actually quite large however the duration is so short that you really don't have time to read that much information out of this door before it's already interfered decayed gone whatever so apparently on this slide it says you can only get three letters but not four but whatever the point must have flashed them on they must flash it up for like a second really fast but the point is if you're just told how many can you get you get about three letters if I queue a specific row right after it goes away you can get three letters from any row which means that at least nine letters are in there anyway the point is this suggests the sensory store holds a pretty complete snapshot of the sensory experience but obviously it fades very quickly so big capacity really short duration back to our Atkinson Schifrin model here so that's the sensory store again everything that you sense goes in this store rattles around in there for a second causes some neural reverberation right whether you're even if you're in a coma if I blow a horn next to your head the sound waves are going to move your eardrum it's gonna move the bones it's gonna cause the snail full of jelly to wiggle and the hairs will move and neurons will fire it'll cause neurons to fire it may be limited to your sensory your auditory cortex but still that's an example of a trace of that stimulus that is memory that may exist only in your sensory store if you pay attention to something like I said then it enters your conscious mind short-term to store working memory which is now called working memory which we already saw hold about seven chunks for about twenty seconds a minute something like that or forever if you keep rehearsing and of course but if you did keep rehearsing it what would happen you wouldn't have to keep rehearsing it forever because you would store it permanently so if you can take your mind off something and then get it later that's proof that it's made it into the long-term permanent storage not permanent necessarily but you know what I mean and initially these guys said okay it's a tension that moves things from a sensory store to the short-term store and it's rehearsal that moves things from the short-term store into the long-term store and it is true that if you rehearse something over and over there's a pretty good chance it will make it into long-term memory what is the capacity of your long-term memory obviously it's huge hopefully everything you know is in long-term memory and how long can it hold it for you know a lot of stuff gets lost from there but there's some stuff that sticks around your whole life and always your first memories from when you were six or four or seven or something like that there you go if you live to be 90 that's 85 years pretty pretty long time all right so there's an introduction to that model which introduces the idea of sensory store which is interesting we're not gonna focus on a lot some people do but it is an interesting memory store that model is very influential like I said there's a lot of good evidence that there's distinctions between those systems however it was an old information processing model it's a little too linear and focuses too much just on the flow of information from the outside world into the model we call that bottom up and not enough on top down influence that is how important what's in long-term memory is for what happens in the sensory store and in the short-term store so that whole like box line next box line next box is kind of an outdated way of modeling cognition cognition is much more like a spiderweb of things happening all at once not this happens then this happens then this happens the brain is a parallel processor we say not a serial processor however this slide just illustrates some important distinctions between the short term memory system and the long term memory system short-term memory describes stuff that you are consciously currently thinking about there's a lot of stuff in memory that you're not thinking about that's in long-term memory short-term memory you can access very rapidly stuff is you know readily available to your conscious mind you can grab it right there in your mental workspace long-term memory might take a little longer because you have to go find stuff in the giant vault of information so to speak short-term memory is capacity limited we saw you can hold about seven things but not much more long-term memory there's really no limit on how much you can hold it long-term memory obviously short-term memory doesn't last as long things are forgotten quickly worse stuff can stay in long-term memory for your whole life okay so while the Atkinson Schifrin model remains influential it generally conceived of the short-term store as a storage place a storage system that conceptualization of short-term memory has largely been replaced by a conceptualization wherein short-term memory is not just a storage system but also a system for manipulating moving controlling getting controlling information manipulating information it's like your mental workspace and the processes that go with it obviously in order for you to do some math or manipulate a concept you have to be able to store it and hold it right so storage is a big part of that system but it's not the only part because manipulating information holding stuff in an active state and even the act of refreshing it for example rehearsing a phone number is an active process you're not it's not a passive it's not like putting a more in a cup and having it just sit there you're actively sequentially going through in time and refreshing bit by bit the elements of your list so having added this active component to the short-term memory system we call it working memory so battling in hich were the first to officially propose this model of short-term memory as a system that includes a processing and information manipulation component as well as the usual storage components and in fact they coined the term working memory and like I said they said yes you really should count the short-term memory system as not just a system for storing stuff but also manipulating information and you really kind of can't do one without the other so you know for example if you're doing mental arithmetic four plus seventeen was 20 plus two you have to maintain representations of those numbers mush 4 and 17 together that's manipulation of information then you got 21 you have to store that because that's not on the screen and mush that together with 20 and so on and so forth so you can see how a simple process like this involves both the manipulation and storage of information to do almost any kind of cognitive process and the system in which this happens might be called your working memory system the model they proposed was very influential and still is today and had several different components which are pictured here the orange pinky parts are the working memory system and then the green part is just basically supposed to represent long-term memory that obviously interacts with the working memory system so the long-term memory here in green is labeled crystalized system and the working memory components above are called fluid systems and this is just to get the idea that stuff that's in long-term memory is kind of hard baked in there and it's crystallized whereas the contents of working memory is is constantly changing depending on what you're thinking or doing you call certain stuff up from long-term memory and activate it in the working memory system and then you deactivate it and call something else up and that gets replaced it's a fluid system and it consists of initially it was just three parts the Central Executive which is not a storage buffer per se but a set of control processes like it monitors error it maintains a representation of current goals so that your behavior can be shaped to achieving those goals internally formulated and maintained goals as opposed to external goals like go chase the shiny thing it controls attention it helps you not process things that you need to ignore in order to get your goals done processes like that that's why those are called control processes it's so to some extent it controls what the contents of current working memory system is the visuospatial sketchpad and the phonological loop two squares below that our storage buffers those are places for holding information for short periods of time in a activated and readily accessible state the visuospatial sketchpad is for holding visual spatial types of information like pictures in your head and where stuff is whereas the phonological loop is used for storage of speech based or sound based information so I mean it's all information mm but actually how it's kind of coded the format is represented in can be pictorial or sound-based turns out there's actually some pretty good evidence that the storage places for those in short-term storage hold buffers are partially distinct different from each other mainly these this evidence comes in the form of finding that trying to store or manipulate to sound based representations at the same time results in interference same thing for to image picture or spatial based things but maintaining and manipulating one sound based in one picture or visual based representation at the same time they don't seem to interfere with each other as much suggesting those are relatively independent storage buffers then later people said well wait a minute how where do you store a representation of an episode of an event right like the mental time travel kind of experience you have when you go back and think about going out to dinner last night that kind of episode that makes up episodic memory representation is kind of special it has you know visual parts to it sound parts taste parts smells emotions all sorts of stuff and there's a lot of evidence that those episodes need a place to be kind of represented as unified entities and so later they stuff that episodic buffer in and it is a place where you can it's a storage buffer that for the central executive to use where it can kind of mush together speech based stuff and visual spatial stuff and other type of stuff into unified representations and episodes are one type of representation that might combine visual spatial and phonological stuff into one chunk or unit and so that might help you remember episodic buffer and of course these working memory systems interact with long-term memory all the time picture an elephant jumping off a cliff you just called up from long-term memory where you had in dormant storage so to speak pictures of elephants and activated that picture which caused it to pop it in their mind jumping off a cliff okay this slide presents a kind of brief overview of each of the components that were on the previous slide in words so that you have those in the notes central executive kind of like the boss of the whole system controls attention then what goes in or out of the other components again it's not a storage place it's a set of processes so the central executive you might say processes information but it's not it doesn't store or hold maintain representations it just influences them phonological loop is used for processing and brief storage of phonological order which includes speech based information visuospatial sketchpad used for processing a brief storage of visual spatial information and again the episodic buffer a system where visual spatial and phonological information can be integrated and maintained in a mush together representation and will look at each of these in a little more detail here so like I said Baddeley and hitch made this model based largely on experiments showing that phone logical stuff interferes with other phonological stuff but not with visual spatial stuff so much and vice versa and on the basis of that they said so there seems to be some justification for separating these two storage buffers into separate pieces in our model and here's an example of some of the data that demonstrate that so in this paradigm people are presented with a chessboard covered in pieces from the middle of a game and asked to select the best move for white or black whatever pick aside and the data that are shown there are the quality of the most election so higher on the y-axis indicates a better move lower indicates a worse move but before we get to the data we have to understand that there are secondary tasks so that's the primary task doing the best chess move you can while you're doing that you also have to do something else you might call this an interference task this dual task paradigm is a very common tool that cognitive psychologists used to try to figure out if the system's behind the two tasks share neural resources or are the same system or have relatively independent neural resources or systems and basically if they interfere with each other we say hmm those must be trying to use the same brain parts and if you can do both at the same time with no decrement in performance then they must be using fairly independent brain parts so the secondary or distractor tasks in this example are random number generation you just sit there and all out random numbers 11 952 3 709 ah it's hard I set nine twice but random numbers could if even if you're generating random numbers probably you're gonna get some repetitions point is if you just spaced out and try to go on autopilot and generate random numbers you won't you'll start like counting or you'll say one number too much or you'll say a phone number so the point is this random number generation this secondary task which components of that working memory model do you think it occupies or taxes because you're talking it necessarily taxes the phonological loop right formulating speech and executing it occupies the phonological loop and because generating random numbers this kind of heart it requires attention it also requires some central executive all right the next secondary or distractor task is tapping keys in a clockwise pattern so it's just like four pegs on a board or something like that three or four inches apart and you just have to tap the four corners of the board the pegs on each corner being a clockwise pattern at your own pace so this is not particularly hard but it does kind of fill up or occupy which component of the working memory model that's right the visuospatial sketchpad it's a spatial task and therefore is thought to occupy some of the resources associated with the visuospatial sketchpad final distractor or secondary task is just saying seesaw seesaw seesaw seesaw seesaw seesaw over and over and over this is fairly simple however like I said if you're talking you're filling up or occupying or using some of the phonological loop all right so we've got three separate distractor tasks and we'll see that they all have their separate effects on your ability to choose a chess move so now we can look at the data there are green bars and purple bars the green bars are for crappier chess players and the purple bars are for better chess players the difference between those is really not critical not surprisingly the better chess players made better moves in every condition but more importantly let's look at what happens when we add the different distractor tasks so the first bars on the left are the control condition where you're just doing the chess move no secondary task and as you can see the strong players below the crappy players away no surprise there when you add the articulatory suppression which is what they call that seesaw seesaw task as an example of that basically means you have to articulate something with suppresses the phonological loop what happens to the quality of the chess moves so now they're making the chess moves and saying seesaw seesaw seesaw the whole time as you can see nothing the weak chess players actually make marginally better moves probably not significant but the point is adding seesaw has no effect on your ability to pick a good chess move and you might say well so what let's keep looking what happened is when you had the tapping task that's the visuospatial sketchpad suppression the next set of bars as you can see that's a pretty simple task just tapping in a square but look what happens to the quality of the chest nose the nose dive what does this suggest think about it logically like I said tapping in a clockwise pattern and picking a chess move seemed to require overlapping cognitive and neural resources what might those be well tapping in a clockwise pattern like I said probably occupies the visuospatial and if you think about making chess moves what do you need to make a chess move thinking about those that working memory model definitely the vision of spatial sketchpad chess is all about picturing what would happen spatially if I go here he could go there or there and if I go there she could go here or there there then this and there's these all these exploding possibility trees but it's about imagining spatial configurations many moves into the future it's very visual spatial intensive so not surprisingly if I knock you PI your visual spatial sketchpad by requiring unit keep this pattern going it's gonna hurt your ability to imagine future chess moves so what happens when I make you do random number generation well again performance tanks the bars on the far right are quite a bit lower than the control condition in than just saying seesaw seesaw so both the random number generation and the seesaw seesaw condition you're occupying the phonological loop but obviously that's not what's hurting your chess moves there's some other difference between random number generation and seesaw seesaw and it is that like I said you can mindlessly sit there and pair it seesaw seesaw seesaw but you can't do that with random number generation you have to kind of keep track of what you said playing a little bit and try to be random which is hard and requires some central executive and making chess moves requires the visuospatial sketchpad we already determined and clearly also the central executive it's about planning and strategizing those are all classic central executive moves so this is an example of the kind of paradigm a dual task paradigm where you add different secondary tasks and see how they affect the primary task differently and so this suggests that because chess moves don't require the phonological loop you can fill that up while you're making chess moves and it has no effect but as soon as you with the visuospatial sketchpad or the Central Executive then you see a real hit to the quality of the chess moves and this is consistent with the idea that the visuospatial sketchpad and the phonological loop and the Central Executive are partly dissociable neural and cognitive systems so these next few slides are just a demonstration of dual tasks where you've got tasks that rely heavily on the visuospatial sketchpad and the phonological loop so that you can actually do them and you can actually kind of feel the interference when you try to do two visual spacial things or two phonological things at the same time so here for example you've got a visual I'm sorry a phonological secondary task or distracted task just saying seesaw seesaw over and over and you're doing a mental rotation task where you take that image little picture blocky thing on the left and you say if it's the same as the next the first one is it the same as the second one is it the same as the third one is it the same as the fourth one while you're saying seesaw so go ahead and try that say seesaw keep doing it seesaw seesaw seesaw seesaw seesaw and that'll look at each of those one at a time typically people do this by rotating one to match the other and seeing if they line up and see how it feels you can pause it and try that still saying seesaw over and over read this list of words to memorize them then you only give yourself about enough time to read the list you know once or twice keep that seesaw going or you're cheating feel that interference now put your fingers down on the desk and tap spread your fingers out put your hand off that on the desk spread your fingers out and tap first between your thumb and forefinger and your forefinger and your middle finger middle ring ring pinky and then back the other way ring middle index index go back and forth like the Android from the first alien movie you don't know what I'm talking about it's your life keep doing that pattern now you have to be able to do that without looking at it because I want you to look up and do this mental rotation task does the standard match one does it match two does a wrench three does it match for you could probably started to poke your hand we started just tapping one finger you gotta keep that pattern going you feel the interference from that relatively simple spatial secondary task when you're trying to rotate that image in your mind now keep tapping and read this list of words to remember it okay hopefully that just gave you some intuitive sense for the interference that happens when you try to do two phonological things or two visual spatial things at the same time so phonological loop we're gonna look at each of these systems in a little more detail used for processing and brief storage of phonological which includes speech based information I already said that it's what you use to say things in your head so sub vocal rehearsal if I give you a list of words what do you do you start sending them over and over to yourself in your head if you're trying to remember them and it turns out it's kind of like a tape loop in your head that can hold about two seconds of just spoken words once you get much over two seconds maybe a little bit more than that you start to like record over the beginning of the loop again and you can't remember more time than that is a way of thinking about it anyway that kind of acts like that one way that we know these aren't very impressive but supports the idea that you really do represent speech based information as sounds in your head you don't have to if I read words to you out loud you could turn them into pictures of the words and it turns out even if I show you pictures of words you generally recode them as sounds you read them if I showed you a list of words fee then he and need and ly than me you would not probably create a visual image of those all pasted together to try to remember it you'd say them over and over in your head and your phonological loop and there's some evidence that we do this of course if you can kind of tell we do it just by introspection but we need data because we're scientists and some of the data that support this is that a bunch of words that sound very similar are harder to remember than words that don't they may look just as similar but they sound different like it's harder to remember fihi Neely me then BAE ho it odd she and presumably this is because we recode those words even if they're presented visually in two sounds and the fihi Neely means list they all sound us the same so they interfere with each other more and again this is taken as evidence that we really do the format our brain uses to represent words speech based information is a sound based or speech based format also remember how the short-term memory can hold about seven things but if the words take longer to say then you can't hold quite as many so this is true if you take a words that have a lot of letters but few syllables like draft DRA you gh T and then other words with the same number of letters but more syllables so visually they're just as long the one syllable words but phonologically they have more syllables so they take longer to say it turns out that the words with more syllables you can't hold as many of them in your head presumably because you sound them out sub vocally they take longer to say and your phonological loop is like a tape loop that can only hold a certain amount of times worth of stuff so the more syllables you have to say the quicker you run out of that space and then those who speak faster can actually has been shown they can remember more words because they can get stuff in her stuff more quickly in their phonological loop all right the visuospatial sketchpad of course used for processing and brief storage of visual patterns and spatial movements locations so obviously there are some things you don't recode into words when you remember them like if I showed you a face and said hey you remember this dude you would remember that as a picture in your mind's eye right at least that's what it feels like subjectively and of course there's evidence that this is true for example they do studies Vogel's defined the capacity limits of the visuospatial sketchpad using a paradigm where you'll see a picture of between 3 and 12 stimuli like a bell LSU or rabbit etc in different parts places on a computer screen and then about a second gap and you'll see the set come back up on the screen but maybe one of the items has changed to something else or you could have a version where it's moved a little bit and your job is to say which item has changed or moved and with one two three four items people do really well they pretty much get it every time but once you get up you know be above that five six items performance really declines quickly and this is the idea is that you just can't hold the nine separate pictures in one image because it's exceeds the capacity of the visuospatial sketchpad another paradigm that's used to study the visuospatial sketchpad and that's pretty much what this slide is showing is called the delayed non-matching to sample tasks a rather clunky name but scientists are not advertisers are they what happens here is a monkey learns to associate a certain object and the picture on the left a blue disc with a piece of food so like they'll close the door on the monkey and put the disc over a peanut open it moves the disc finds a peanut do it a few times okay blue disk means food then they close the door and they introduce another object of course that the monkey hasn't seen it it's a novel or new object and they always set it up so that the peanut now is always under the new object that's why it's a non matching to sample because when you open the door the monkey needs to learn to look under the new thing not the thing that they used before and the reason why is they don't want this to just be kind of a stimulus response automatic very basic learning mechanism where a blue disc eat blue disc eat rather the monkey has to during the delay maintain a representation of that blue disc so that when the door is opened and there's a new object they know to pick not the thing they had been holding on to so this is just a simple paradigm that's used to study how the visuospatial sketchpad works and if you mess with brains what happens to it and how long what happens to their ability to hold this information as you extend the time periods where the door is down you do a few seconds or you can do you know ten minutes can they hold that blue disc in mind for ten minutes and the rules of the game and finally the episodic buffer like I said is a storage system where info from the phonological loop and the visuospatial sketchpad can be stored and integrated like memory for an episode like going out to east last night or going to the movies last week or whatever obviously those representations those episodic memories have both visual spatial and phonological and other types of information all balled up into them it's also been proposed that episodic buffer is kind of like a little workspace where the central executive can mow stuff together put stuff together screw his stuff and also has been proposed as a place that supports understanding and memory for prose and there's a lot of research on like understanding stories and how understand texts and make mental models of what's happening when you hear a story like a girl walked down the dock and saw a frog on a lily pad the frog jumped off the pad and landed on a log which rolled over and the Frog swam away as you understand that you're forming pictures in your mind's eye and you might be hearing the Frog plop into the water you're making a little mental model a little reality of what's being described in the prose in the text and there's a lot of work into this and it's interesting stuff a lot of that idea when I say mental models and you make a model of reality a lot of those theories come from work in how we understand text and stories and prose but this idea that we need a place where those types of representations can be held as part of what motivated badly and hitch to say okay here's another storage buffer called the episodic buffer and a simple example of just kind of mushing together visual spatial and phonological information is demonstrated by this study described on the bottom here 2010 where there were people task was to remember digits that were presented in three different ways either all in the same place on a computer screen one at a time six three five one nine seven seven five or one at a time but in a row across the screen or one at a time but in the location that they would be in on a phone pad right so the lower left hand screen you'd see a seven then the top right you'd see a three in the middle you'd see a five right above it a two another two and the point is memory was best in the condition where the digits fell in the places they would fall on a foam pad number pad and the thinking is that it's because in addition to the phonological code that you would make when they're all presented in the same place six three five nine now you've also got a spatial pattern that you can kind of tap in your visual spatial sketchpad as you say it right so five you tap the middle then you think about going to the upper right and that helps you remember that it's a three five three just below that is a six and then you remember the pattern then goes to the upper left so you know that's a 1 and you can see how saying and moving at the same time strengthens the memory trace because you're able to recruit both visual spatial and phonological information and the idea here is this may involve the episodic buffer wherein you're integrating those two different kinds of information ooh I said finally for the episodic buffer but we forgot about perhaps the most important or most interesting part of Baddeley's working memory model this central executive or the boss of the whole system again this processes information it doesn't store information and it does it's don't think of this as a little like homunculus guy who's controlling everything that kind of ruins the explanatory power because then who's controlling that guy think of it rather as a set of processes like screening out irrelevant information like maintaining in a currently active state the rules of the game the goals that we have right now what we need to do and what we shouldn't be doing right it biases processing in sensory regions so that you don't get distracted by the conversation next to you at Starbucks when you need to study sometimes you do that would be a failure of your central executive setting goals planning like I said error monitoring if you're kind of on autopilot and then something one of your mental models predictions is wrong and an error signal is generated the Central Executive is the system that generates the error notices it reorients attention until the error signal is reduced because your model is correct and not making any false predictions anymore you know if you're in a totally novel situation you've got to always kind of pay attention and attentional control is another example of an executive function and I haven't talked much about the brain yet and we'll talk about it more later but working memory is associated with the frontal cortex largely particularly the central executive the dorsal lateral prefrontal cortex or DL PFC is often lit up when people are engaged in tasks that require a lot of planning or strategizing or error monitoring or attentional control when they're doing central executive tasks and some of those different functions actually light up subtly different portions of the prefrontal cortex okay because of how interesting and important the central executive and these executive processes are let's get a little more familiar with them before we move on to brain substrates so here is and because it's kind of hard to getting a grip on just saying it's the boss which controls everything is pretty vague right and like I said if it makes you just picture a little guy in control that's not really helping anybody because who's controlling that guy right so let's look at it I said it's a set of processes let's look specifically at some of those processes and some tasks that are used to test those specific control processes and you'll have a pretty good feel for it so functions that are typically considered executive might be listed here on the left and the tasks used to test them on the right and I believe we'll look at each one of these in more detail but controlled updating of short-term memory that is updating what you're currently holding in the storage buffers of working memory that's a task that is considered an executive central executive task and there are cool paradigms used to tax tests this in particular one is the n-back task one is self ordered search and we're gonna see these examples so don't worry about them understanding what they are just yet setting goals and planning strategy making Tower of Hanoi as a task used to test that ability task switching right okay don't do that old tasks anymore the rules are different now we're doing a new task that is a central executive function and of course paying attention to what you need to pay attention to and perhaps more importantly inhibiting or suppressing the processing of irrelevant stimuli and suppressing responses that may be fairly over-learned and automatic but inappropriate at this time require the central executive again we'll see examples of each of these so that first one updating the contents of working memory can be tested using a number of tasks one of them is this self ordered memory task so basically all you do is you see a bunch of pictures on a card one at a time and they're always randomly arranged on each successive card so the pictures aren't always in the same place on each card for example on the first card you can see that top left has geese in it and the second card the geese are in the bottom middle so it's always the same six pictures but they're on in different places on each card each time a card comes up your job is to just pick one of the pictures and then on the next card pick a different one other pictures and on the next card yet another different one of the pictures the point is to pick a different picture on each card you never want to repeat one you've already picked until you get through all six so if you think about it what do you have to do to do this task and you can make it harder or easier by having more pictures on each card but starts off super easy right just point to one but you got to remember it I pointed to the Rose on the second card just point to another one and I pointed to the goat then on the third card just point to another one I pointed to the geese and all the while you have to start off by storing rows then when you point to the goat you have to update the contents of working memory to be rose goat and then after the third card you have to update it again to be Rose go geese and so on and so forth so you have to constantly be adding items and holding onto the previous ones at the same time so that's why we call this a updating task where you're updating the contents of working memory and you know it's not rocket science but it's a task that you know is trying to isolate a specific executive function if you think of it that way it's pretty clever for planning and goal maintenance like I said the Tower of Hanoi you guys are probably seeing this before the goal here is to get the stack of disks from a the a pole to the C pole you can only move one disk at a time and you can never put a bigger disk on top of a smaller disk so you can just start randomly throwing discs around or three disks it's super easy you get it eventually but one way to do it is to set a little sub goal like well first I need to get the red and the green disc on B so I can get that big blue one from A to C how do I do that well I put the red one on see the green one on B and then B and I can move the blue one over the C and then what do i do from there pretty straightforward but you can see how you're picturing moves in your mind's eye to see what the results would be to pick the correct sequence it's kind of like playing chess except much easier with three disks however if you look at the bottom where we've got ten disks that would take and I think there's something like this originated with monks or something in the Himalayas but that would take you like the rest of your life to figure out so three disks is stupidly easy but if you put a lot of distance on there it gets incredibly hard anyway when you hear the term Tower of Hanoi now you know what it is more importantly you know what psychologists use it to test strategy making and planning and goal maintenance as well all of which are false squarely under the category of executive functions another executive function is task switching which is exactly what it says it is and is tested using the Wisconsin card sorting test another value for introducing these to you is because these may be tests that you come across in your clinical professional life and now you will have a level of understanding of exactly what they're meant to test and how that fits in the larger picture of cognitive abilities and processes then you might have if you hadn't taken this course anyway Wisconsin card sorting task you got a bunch of cards and you're flipping them over one at a time and you're just categorizing them and at first you might go I don't know I guess I'll categorize them on the basis of color so you start doing that and if it's right you get feedback on each trial yep good if it's wrong you go oh maybe I should be categorizing them on the basis of shape whatever eventually you figure out what the rule is the task okay I need to categorize them based on color pretty easy you're going along then you don't barely have to think about it anymore then all of a sudden you put a red on red and it says wrong you're like oh no the task has switched then you have to figure out what the new task is maybe they're being I need to sort them on the basis of shape maybe I need to sort them on the basis of numerosity but all the ones in the five ones together five together fours together anyway eventually you discover the new rule and you keep going according to the new rule well what's important in this task is not just how quickly you discover the new rule but whether you're able to remember and not commit any per separative errors we call that is where you momentarily space out and go back to the old rule all right that is a failure of your executives ability to effectively maintain the tasks which the new goal set and typically this task is done with patience and if yeah I don't know if you hadn't we've talked about why you would have any reason to be able to predict what patients are particularly bad at this are likely to commit more per separative errors but those patients you might go whom they may have some executive deficits involving the frontal lobe schizophrenic s-- for example tend to commit a lot of perseverate of errors on their wisconsin card sorting tasks our old friend the Stroop task another executive function i mentioned is the ability to inhibit prepotent but inappropriate responses and by prepotent i mean ones that are kind of automatic and to control attention to the features elements stimuli in the environment that are relevant for the current goal set so Central Executive is important for selecting appropriate behaviors inhibiting inappropriate behaviors the Stroop task is a classic test of this ability I expect you've all heard about it but basically you see words appear in different ink colors then your task is to name the color of the ink when you're describing a Stroop task to someone even if you know what it is people always make it not clear because a key to remember is that you've got to use the word ink color because people always like you say the color well blue written in blue ink the color of the word is blue both ways the point is your task is to name the ink color and the trials can be congruent or the ink color and the letters that make up the word make the same color the first example blue and blue ink incongruent trials where you've got the word blue and red ink you should say the Stroop effect is how much you slow down or make mistakes when you have to say read on in congruent trials where the word says blue because even though you're not supposed to read the word it has nothing to do with the task your central executive is saying don't read the word just name the ink color still we can't help but activate the meaning of the word because that's an automatic response for us even if you see a word and you're trying not to read it at some level the meaning of that word is still activated in your head and since blue is incongruent with red we slow up and screw down a little bit more on incongruent trials compared to congruent trials the extent to which we slow down the larger the Stroop effect we show indicates that we might have poorer attention executive function in this regard because we are less efficient at suppressing that automatic reflex to read the word because remember you go you don't go around the word the world naming the colors of words you go around the world reading words it has become an automatic response to a word to read it activate its meaning that's what I mean when I say it's a prepotent response so if we just relaxed and spaced out and kind of respond in an automatic fashion we're much more likely to read the word than name the ink color so that's why the Stroop task really requires this involvement of the executive over long periods of time to keep the clamps on processing and make sure you don't slip back into that easy automatic response where you just read the word in fact you always have to suppress that in order to as quickly and efficiently as possible made an ink color want to try it sure you do ready remember a name color do it what who what you do now blue what black all right so the correct responses of course are green red blue and black and these are all incongruent examples and you can tell us if you try to go fast it you can feel that interference but it's your central executive that is helping you suppress what the word says in order to name the ink color