1 Maguire (1997) Study on Memory of Routes AICE AS Level Psychology Lecture 1

Recalling Routes around London: Activation of the Right Hippocampus in Taxi Drivers. Journal of Neuroscience. 17(18), September 15. pp. 7103–7110 2

A. Important definitions – 1. Episodic memory = is the memory of autobiographical events (times, places, associated emotions, and other contextual who, what, when, where, why knowledge) that can be explicitly stated. – 2. semantic memory – well known; refers to general world knowledge that we have accumulated throughout our lives

– 3. Neural substrates is a term used in neuroscience to indicate a part of the nervous or brain system that underlies a specific behavior or psychological stateneurosciencenervousbrain – 4. Neural instantiation – the creation of memories at the cellular level. – 5. The Knowledge – The test for taxi cab drivers in London – 6. rCBF = regional cerebral blood flow – as measured by a Pet Scan

– 7. Two factors design – the researcher is looking at the effects of two factors and possible interaction effects of the two factors on a response variable (location in the brain for this experiment). – 8. Extrastriate Region is the region of the occipital cortex of the mammalian brain located next to the primary visual cortex, which is also named striate cortex because of its striped appearanceoccipitalcortexprimary visual cortex

B. Previous studies had examined spatial memory as part of episodic memory. – 1. they used fMRI to examine a persons recall of spatial layouts using virtual reality – 2. they found that “environmental knowledge is not represented in one system but spread around the neocortex” (cerebral cortex). 6

C. This study looks directly at the use of memory of the environment that through use has become so engrained in our memories that it has become part of semantic or general knowledge memory D. Some case studies on patients with topographical disorientation in familiar environments indicate that this may be the case 7

A. This study has 3 aims – 1. The first aim of this study was to examine semantic (well known) topographical (maps) memory retrieval and to determine whether recall of well- established spatial layouts activates similar brain regions noted in other studies a. In other words they wanted to replicate the work of previous studies. 8

– 2. The 2 nd aim of the current study was to assess the neural instantiation (creation) of landmark knowledge, where such knowledge was not confounded by location information about position within a large-scale spatial layout. a. This was achieved by using a task in which famous landmarks were known but the subjects had never visited them. b. In other words they wanted to see if all location type memories are stored in the same place 9

– 3. A final aim of the study was to examine topographical memory and also non-topographic semantic memory retrieval to ascertain whether common brain regions subserve semantic memory regardless of memory type. a. In other words they wanted to see if semantic memories of all types were stored in the same region. 10

A. The Sample – 1. Used licensed taxi drivers from London a. 11 male, right-handed with an avg age of 45 b. All between 3 and 27 years of taxi driving experience with an average of years. c. None had any Hx of previous mental illness. 11

d. All taxi drivers in London must undergo a two year course of study known as “The Knowledge” demonstrating complete knowledge of the streets of London. e. Scans done under the certification by the Administration of Radioactive Substances Advisory Committee. f. Remember that PET scans use a radioactive form of glucose g. All Ps gave written informed consent 12

B. Scanning techniques – 1. PET scans were obtained using a Siemens/CPS ECAT EXACT HR1 (model 962) PET scanner (all using same machine = control) – 2. The system allows the activation frame to be triggered automatically, depending on the physiology of the individual subject. (control) 13

C. Data Analysis – 1. Images were analyzed using Statistical Parametric Mapping executed in MATLAB – 2. This approach allows researchers to make statistical inferences about regional blood flow effects 14

Cue 1: In your own words what is the difference between an MRI and a PET scan? Cue 2: Pick 1 of the aims of the study and restate it in YOUR OWN words Cue 3: Why do you think this sample is so small? What other critiques can you make about it? Cue 4: Describe the PET scan machine used in this study.

16 Maguire (1997) Study on Memory of Routes AICE AS Level Psychology Lecture 2

D. Experimental Tasks – 1. There were six tasks, each performed twice, with task order counterbalanced within and between subjects; five of the tasks are relevant to this discussion. – 2. Therefore this is a repeated measures design – 3. It is also a TWO FACTORS design – see previous definition in video 1 – one factor is topographical the other is sequencing

– 2. Two of the tasks involved topographical knowledge: a. in one, taxi drivers were given a starting and destination points in the greater London area. b. They had to describe overtly during scan acquisition the shortest legal route between the start and destinations

c. The other topographical task involved recalling and describing the appearance of individual world-famous landmarks (not in London) that subjects had never visited. d. The important difference between these two topographical tasks is that the route requires sequencing whereas the description of the landmark does not. 19

– 3. Two non-topographic tasks were also included to engage subjects in semantic memory retrieval in a manner similar to the topographical tasks, but without involving the recall of environmental spatial information. a. These tasks concerned memory for films b. recalling and describing the plots of familiar famous films between given points in the story line, which like the recall of routes involves a set sequence of information retrieval 20

c. Recalling and describing individual frames from famous films, not the plot of the film, which does not involve any necessary sequence of information

T = Topographical S = Sequencing – T+/S+ = routes – T+/S- = landmarks with no topographical knowledge – T-/S+ = Film with plots (sequencing) – T-/S- = Film frame memory – no sequence 22

– 4. A baseline task to control for speech output was included in which subjects repeated two four- digit numbers during scanning. Comparison with this baseline facilitated examination of the network of brain regions involved in each task by indicating whether changes of activity were relative or absolute in relation to it. – 5. Subjects were blindfolded throughout, and speech output was digitally recorded. 23

– 6. Before they arrived for scanning, subjects completed and returned questionnaires that inquired about the following: a. areas of London with which they were most familiar; b. films they would rate as very familiar, from a list of 150 color films made between 1939 and the present day; and c. individual landmarks from a list of 20 world-famous ones they had NOT visited in person BUT could visualize in their mind’s eye. 24

d. Routes from areas of London with which all subjects were familiar were chosen as stimuli in the routes recall task. e. Those films that all subjects selected in common as being very well known were used as stimuli in the film plots and film frames tasks. – These were films that subjects were thoroughly familiar with and had generally seen five or more times, with no memory for where, when, or with whom they had seen the film (thus no spatiotemporal reference and therefore semantic memories). 25

– 7. Famous landmarks selected in common across subjects as those they could visualize but had not visited in person were selected. Landmarks that had not been visited by any subject were selected to prevent subjects from recalling landmark locations within a spatially extended environment, thus assessing the neural basis of the landmarks per se as the most primary elements of topographical knowledge. 26

Cue 6: What is meant by the term counterbalanced? Cue 8: How is this set up similar to the Nelson Set up? Cue 9: Why were the subjects blindfolded throughout?

28 Maguire (1997) Study on Memory of Routes AICE AS Level Psychology Lecture 3

A. Summary of results – 1 The goal of the study was to engage subjects in the relevant task for the duration of each scan. All subjects performed the tasks fluently, without stopping. (This shows that the Ps could do the task easily) 29

Table 1. Duration (seconds) of speech across the five tasks Task Mean SD Range Routes –75 Landmarks –70 Film plots –70 Film frames –68 Baseline number repetition –76 This table shows the mean duration of speech for each of the tasks that occurred over the 90 second duration of scan acquisition. – No significant differences in speech duration between any of the main tasks – Given repetitive nature of the tasks, more speech occurred during the baseline number repetition

– 2. It was notable that the routes chosen by subjects during the navigation task were all very similar, with small differences in the minor roads selected. Street names were recalled accurately, as were relevant landmarks, and traffic restrictions were adhered to. – 3. Subjects were debriefed after scanning and reported visualizing actual travel along the routes, including “seeing” salient landmarks as they were passed. 31

Pick up on Grosvenor Square in Mayfair, drop off at Bank Underground Station, then at the Oval Cricket Ground... “Grosvenor square, I’d leave that by Upper Grosvenor Street and turn left into Park Lane. I would eh enter Hyde Park Corner, a one-way system and turn second left into Constitution Hill. I’d enter Queen Victoria Memorial one-way system and eh leave by the Mall. Turn right Birdcage Walk, sorry right Horse Guards Parade, left Birdcage Walk, left forward Great George Street, forward into Parliament Square, forward Bridge Street. I would then go left into the eh the Victoria Embankment, forward the Victoria Embankment under the Blackfriars underpass and turn immediate left into Puddledock, right into Queen Victoria Street, left into Friday Street, right into Queen Victoria Street eh and drop the passenger at the Bank where I would then leave the Bank by Lombard Street, forward King William Street eh and forward London Bridge. I would cross the River Thames and London Bridge and go forward into Borough High Street. I would go down Borough High Street into Newington Causeway and then I would reach the Elephant and Castle where I would go around the one-way system.... ” (end of scan). 32

– 4. During the tasks describing film plots and frames and famous world landmarks, subjects reported that they recalled the films/frames/landmarks from memory as if they were looking at them. – 5. The film frames were described as if in “freeze frame,” with no mention of sequential plot action but merely descriptions of who was in the scene and other visual information. 33

– 6. Rich descriptions of landmarks were provided, with many details recalled. Overall, subjects denied recalling any specific spatiotemporal context related to any of the information retrieved. B. PET results – 1. Comparison of BASELINE with ROUTES TASK a. Comparison of the activity during the routes task with the baseline revealed bilateral activity in extrastriate regions, the medial parietal lobe, the posterior cingulate cortex, and parahippocampal gyrus, and also activation of the right hippocampus. 34

Brain RegionRoutesLandmarksPlot/Frame Extrastriate RegionYesNo Medial Parietal LobeYes No Posterior Cingulate NucleusYes No Parahippocampal GyrusYes No Right HippocampusYesNo Frontal RegionsNoYes Occipito-Temporal RegionsNoYesNo Middle Temporal GyrusNo Yes Left Anglular GyrusNo Yes CerebellumYes Left Temporal LobesYes

b. There was no significant activation of frontal regions associated with this comparison. – 2. Comparison of BASELINE with LANDMARKS a. The landmarks task compared with baseline also resulted in activation of the posterior cingulate cortex, the medial parietal lobe, and occipitotemporal regions, including the parahippocampal gyrus b. In this case, however, there was no activation of the hippocampus, but there was significant activation of left inferior and middle frontal gyri. 36

– 3. Comparison of BASELINE with FILM SCENES (BOTH) a. activated left frontal regions, middle temporal gyrus (plots left, frames right), and left angular gyrus but not medial temporal areas. – 4. Summary of results a. In summary, the answer to our first question is that the network of brain regions, including the right hippocampus, that supports semantic topographical memory retrieval is similar to that noted in a previous study 37

b. The answer to our second question, specifically inquiring about the neural instantiation of landmarks, is that both retrieval of landmark knowledge and retrieval of complex route information activate many similar brain regions, but the right hippocampus is activated only during routes recall. 38

C. Main effects – 1. In the design of experiments and analysis of variance, a main effect is the effect of an independent variable on a dependent variable averaging across the levels of any other independent variables. design of experimentsanalysis of variance

– 2. Comparison of the activity during routes recall with activity during any of the other conditions revealed significantly increased activation of the right hippocampus. – 3. This confirms that activity in the right hippocampus is increased during routes recall, as in topographical encoding (Maguire et al., 1996a), but is not increased during the recall of landmarks. 40

D. Compound Main effects – 1. comparing the two topographical tasks to the film tasks a. There was increased activation of the bilateral medial parietal regions, the posterior cingulate cortices, fusiform gyri, and parahippocampal gyri during topographical relative to nontopographical memory retrieval. b. In summary, the answer to our third question is that the network of brain regions showing increased activation during semantic topographical memory retrieval are entirely different from those activated during retrieval of nontopographical semantic memory. 41

Cue 10: Describe one result that supports aim 1? Cue 11: Describe one result that supports aim 2 Cue 12: Describe one result that supports aim 3

43 Maguire (1997) Study on Memory of Routes AICE AS Level Psychology Lecture 4

A. Retrieval of Route Knowledge – 1. The aim of the present study was to examine semantic topographical memory retrieval and to determine whether recall of well established spatial layouts activates similar brain regions noted in other studies to subserve episodic topographical memory. – 2. Recall of routes around London by taxi drivers in the present study activated the same brain regions compared with a baseline task. 44

– 3. Thus, for topographical memory at least, the distinction between episodic and semantic memory seems to have no anatomical basis. – 4. This is consistent with animal work that documents the importance of the hippocampus in allocentric mapping of space – 5. This observation indicates a role for the right hippocampus in processing spatial layouts over long time courses not assessed by the short time scales of previous studies 45

– 6. Previous studies that did not find this area of the hypothalamus to be activated used computer- simulated environments, whereas the present study involved memory for real-world environments. – 7. Real environments are more complex than the simulations used to date (This was 1996, could virtual reality have improved…think Google maps at surface level) and involve the potential for using many routes to navigate to a goal, as reflected in the task put before the taxi drivers to find the shortest route to a destination. 46

– 8. The absence of activation of the hippocampus in the two simulation studies that used novel stimuli and the fact that taxi drivers were familiar with the routes in the present study make it unlikely that hippocampus activation in topographical memory tasks is attributable to novelty of stimuli 47

B. Retrieval of Landmark Knowledge – 1. The current study also set out to assess the neural instantiation of landmark knowledge where such knowledge was not confounded by location information about position within a large-scale spatial layout. – 2. The involvement of many of the same brain regions in routes and landmarks memory indicates that the topographical memory system is primed for relevant topographical information even when the landmarks, as in this case, have no spatial connotation. 48

– 3. Our findings support the view that there was no evidence for distinct mechanisms for the identification of environmental features on the one hand and their location on the other. C. Semantic Memory – 1. A final aim of the study was to examine topographical memory and also nontopographic semantic memory retrieval to ascertain whether common brain regions are involved regardless of memory type. 49

– 2. Recall of film plots was associated with brain regions different from those activated during the routes task. 50

A. Ethics – 1. Pro - all participants gave consent for scans – 2. Con - scans may be uncomfortable. B. Strengths – 1. Controls a. The sample consisted of all experienced taxi drivers b. The thinking tasks were highly controlled for previous experiences and past knowledge 51

c. This was a physiological study which implies the use of scientific equipment which is seen as reliable. d. The same machine was used throughout the experiment – 2. Validity of measures – the measure of rCBF (regional cerebral blood flow)allows them to make statistical inferences to compare results. 52

3. Reductionist, that is it allows for simple explanations of a behavior. In this case the right hippocampus is involved in these type of topographical tasks. C. Weaknesses of the study – 1. Ecological validity – is imagining routes the same thing as happens in the real world? – 2. Reductionist nature (making everything explained by a simple structure) may limit its usefulness and generalizability to other areas 53

– 3. Related to this is the fact that the researchers take a very DETERMINISTIC stance in that they assume all behavior can be explained physiologically. – 4. The sample only consists of white males and was small

A. Usefulness – – 1. provides an explanation of how topographical tasks are handled by the brain as compared to other memory tasks. – 2. This explanation however may be too reductionist. B. Further studies and alternative Methodology – 1. Possibly using new technology to simulate moving in 3d world. 55

– 2. Extend to women as women may map the world differently than men – 3. Use a case study method where participants are studied from the time they begin training for their taxi license and compare these as they progress through training to see if there is a change in the hippocampus. – 4. Have the subjects learn new routes through a simulated city to see how learning is encoded to these areas as opposed to how it is retrieved. 56

Cue 13: How can the fact that this study is reductionist in nature be both a positive and a negative? Cue 14: What is a strength and weakness of the lab method