Spatial learning and the 'inner GPS' in the mammalian brain

Question 1

How do animals learn spatial locations and routes?

Answer 1

• WM - remember places within a trial (e.g. remember which arms already visited)
• Reference memory - remember places between trials (e.g. remember which arms contain food)
• Rats learn spatial r’ships between arms and external landmarks rather then following a rule or marking visited arms
• Which tests/evidence required for this conclusion?
Rotate the maze - change config of external landmarks

see notes

Question 2

How do animals learn spatial locations and routes? research

Answer 2

Olton and Samuelson (1976)

Barnes (1988)

Question 3

Olton and Samuelson (1976)

Answer 3

maze had barriers so couldn’t see rest of room
Tested 24 male albino rats on an 8-arm maze in a paradigm of sampling with replacement from a known set of items until the entire set was sampled. Exps I-III demonstrate that Ss performed efficiently, choosing an average of more than 7 different arms within the 1st 8 choices, and did not utilize intramaze cues or consistent chains of responses in solving the task. Exps IV-VI examined some characteristics of Ss’ memory storage. There was a small but reliable recency effect with the likelihood of a repetition error increasing with the number of choices since the initial instance. This performance decrement was due to interference from choices rather than just to the passage of time. No evidence was found for a primary effect. The data also suggest that there was no tendency to generalize among spatially adjacent arms. Results are discussed in terms of the memory processes involved in this task and human serial learning

Question 4

Barnes (1988)

Answer 4

There are a number of ways to approach the problem of how nervous systems are modified in response to an organism’s interaction with its environment. One of these has been the study of learning and memory processes in the rat and their underlying physiological mechanisms, an endeavor that has contributed significantly to the overall understanding of the neural basis of behavior. As an example, the neurobiological properties of the rat hippocampal formation in relation to spatial information processing are reviewed, including a variety of behavioral analyses in conjunction with lesion and electrophysiological recording techniques. These approaches have furthered our understanding of cognitive operations that involve the integration of multiple sensory stimuli leading to the production of complex adaptive responses.

Question 5

Hippocampal lesions impair spatial learning

Answer 5

• Humans
○ Declarative (facts) memories can be lost with hippocampal damage, but not procedural (skills) memories - often old memories are not lost
• Animals
○ Hippocampus imp for acquisition of new info and spatial learning
Control condition in hippocampus. Lesion studies - non-spatial learning (cued learning) - shows can perf other types of learning but doesn’t form spatial memories

see notes

Question 6

Hippocampal lesions impair spatial learning research

Answer 6

Barnes (1979)

Morris (2008)

O’Keefe and Nadal (1979)

Ruskin et al. (2004)

Question 7

Barnes (1979)

Answer 7

○ Circular platform maze
- Neurophysiological and behavioral measures were obtained from 32 senescent (28–34 mo) and 32 mature adult (10–26 mo) Long-Evans hooded rats. Extracellularly recorded synaptic responses were obtained from electrodes chronically implanted in the fascia dentata and perforant path. Ss were first tested on a circular platform, which favored the use of spatial cues for its solution; the senescent Ss exhibited poorer memory for the rewarded place. When granule cell synaptic responses were recorded after a single session of very brief high-frequency stimulation, the amount of elevation and time course of decline were equivalent between age groups. After 3 repetitions, however, young Ss maintained the increased synaptic strength for at least 14 days, whereas old Ss declined after the 1st session. The amount of synaptic enhancement was statistically correlated with the ability to perform the circular platform task both within and between groups. Furthermore, the aftereffects of the high-frequency stimulation selectively impaired the old Ss’ spontaneous alternation behavior on a –T maze. Results are discussed in terms of the synaptic theory of memory formation and the aging process.

Question 8

Morris (2008)

Answer 8

TheMorris water mazeis one of the most widely used tasks inbehavioral neuroscience for studying the psychological processes and neural mechanismsof spatial learning andmemory. The basic task is very simple. Animals, usually rats or mice, are placed in a large circular pool of water and required to escape from water onto a hidden platform whose location can normally be identified only using spatial memory ( Figure1). There are no local cues indicating where the platform is located. Conceptually, the task derives fromplace cellsthat areneuronsin thehippocampuswhich identify or represent points in space in an environment (O’Keefe, 1976).
It was developed by Richard Morris at the University of St Andrews in Scotland and first described in two publications in the early 1980s (Morris, 1981; Morris et al., 1982). Place navigation in the watermaze is now often used as a general assay of cognitive function (Brandeis et al., 1989), for example for testing the impact of various disturbances of thenervous system(e.g. animalmodels of stroke(Nunn et al., 1994), aging (Gallagher and Rapp, 1997), neurodegenerative disease (Hsiao et al., 1996), or the potential impact of novel therapeutic drugs (D’Hooge and De Deyn, 2001). The task has also inspired computational neuroscientists and roboticists interested in navigation (Krichmar et al., 2005).

Question 9

O’Keefe and Nadal (1979)

Answer 9

○ Theories of spatial cognition are derived from many sources. Psychologists are concerned with determining the features of the mind which, in combination with external inputs, produce our spatialized experience. A review of philosophical and other approaches has convinced us that the brain must come equipped to impose a three-dimensional Euclidean framework on experience – our analysis suggests that object re-identification may require such a framework. We identify this absolute, nonegocentric, spatial framework with a specific neural system centered in the hippocampus.
○ A consideration of the kinds of behaviours in which such a spatial mapping system would be important is followed by an analysis of the anatomy and physiology of this system, with special emphasis on the place-coded neurons recorded in the hippocampus of freely moving rats. A tentative physiological model for the hippocampal cognitive map is proposed. A review of lesion studies, in tasks as diverse as discrimination learning, avoidance, and extinction, shows that the cognitive map notion can adequately explain much of the data.
- The model is extended to humans by the assumption that spatial maps are built in one hemisphere, semantic maps in the other. The latter provide a semantic deep structure within which discourse comprehension and production can be achieved. Evidence from the study of amnesic patients, briefly reviewed, is consistent with this extension

Question 10

Ruskin et al. (2004)

Answer 10

Prolonged sleep deprivation results in cognitive deficits. In rats, for example, sleep deprivation impairs spatial learning and hippocampal long‐term potentiation. We tested the effects of sleep deprivation on learning in a Pavlovian fear conditioning paradigm, choosing a sleep deprivation paradigm in which REM sleep was completely prevented and non‐REM sleep was strongly decreased. During conditioning, rats were given footshocks, either alone or paired with a tone, and tested 24 h later for freezing responses to the conditioning context, and to the tone in a novel environment. Whereas control animals had robust contextual learning in both background and foreground contextual conditioning paradigms, 72 h of sleep deprivation before conditioning dramatically impaired both types of contextual learning (by more than 50%) without affecting cued learning. Increasing the number of footshocks did not overcome the sleep deprivation‐induced deficit. The results provide behavioural evidence that REM/non‐REM sleep deprivation has neuroanatomically selective actions, differentially interfering with the neural systems underlying contextual learning (i.e. the hippocampus) and cued learning (i.e. the amygdala), and support the involvement of the hippocampus in both foreground and background contextual conditioning

Question 11

Navigation (Wolf, 2011)

Answer 11

• Getting from one point to another point
• Where am I? - reference to an abstract map, allocentric representation, allows to plan for novel route without learning it
• How do I get from here to a goal location? - following learned routes, novel routes link to learned information, egocentric and allocentric representations
• Multimodal sensory info used
• Cognitive map: using visual allocentric cues in an object-centred reference frame to infer direction and distance - no other animal can do it as well as we can
• View-matching: inferring direction and distance from views that are matched with memorised views in an egocentric frame of reference (e.g. retinotopic maps) - everything in relationship to your body
• Path integration (dead reckoning): updating location and directional orientation by recording idiothetic cues, over long distances (turns, no. of steps, odometry); prone to cumulative error
• Path integration in the desert ant Cataglyphis
○ Has to run v. fast
○ High legs because of heat
○ Has to have well adapted navigation system
○ Have to search and find food - don’t have many landmarks - use path integration - count number of steps - goes in straight line home - knows where it is because of path integration
- Path integration v. inaccurate - larger distance = larger error

see notes

Question 12

Wolf (2011)

Answer 12

Animals have needed to find their way about almost since a free-living life style evolved. Particularly, if an animal has a home – shelter or nesting site – true navigation becomes necessary to shuttle between this home and areas of other activities, such as feeding. As old as navigation is in the animal kingdom, as diverse are its mechanisms and implementations, depending on an organism’s ecology and its endowment with sensors and actuators. The use of landmarks for piloting or the use of trail pheromones for route following have been examined in great detail and in a variety of animal species. The same is true for senses of direction – the compasses for navigation – and the construction of vectors for navigation from compass and distance cues. The measurement of distance itself – odometry – has received much less attention. The present review addresses some recent progress in the understanding of odometers in invertebrates, after outlining general principles of navigation to put odometry in its proper context. Finally, a number of refinements that increase navigation accuracy and safety are addressed.

Question 13

Pointing tasks (Ekstrom et al., 2014)

Answer 13

• Accuracy can be increased in a JRD task
• Humans may rely on allocentric knowledge for some tasks
• Most ethological situs can be solved with both, and there could be continuum how each contributes
• SOP - visual cues - use egocentric info - primed by presence of objects
• JRD - more accurate as given more reference points - allocentric
Difficult to tell the 2 apart

see notes

Question 14

Pointing tasks (Ekstrom et al., 2014) research

Answer 14

Epstein and Vass (2014)

Question 15

Epstein and Vass (2014)

Answer 15

Humans and animals use landmarks during wayfinding to determine where they are in the world and to guide their way to their destination. To implement this strategy, known as landmark-based piloting, a navigator must be able to: (i) identify individual landmarks, (ii) use these landmarks to determine their current position and heading, (iii) access long-term knowledge about the spatial relationships between locations and (iv) use this knowledge to plan a route to their navigational goal. Here, we review neuroimaging, neuropsychological and neurophysiological data that link the first three of these abilities to specific neural systems in the human brain. This evidence suggests that the parahippocampal place area is critical for landmark recognition, the retrosplenial/medial parietal region is centrally involved in localization and orientation, and both medial temporal lobe and retrosplenial/medial parietal lobe regions support long-term spatial knowledge.

Question 16

What about mice? (Rinaldi et al., 2020)

Answer 16

• Allocentric navigation not only dependent on hippocampus but also distributed neural circuits (dorsomedial striatum, nucleus Accumbens, prelimbic and infralimbic cortex)
- Retrieval of allocentric and egocentric info mediated by distinct neural systems - activate diff neural networks

see notes

Question 17

What about mice? (Rinaldi et al., 2020) research

Answer 17

Hok et al. (2016)

Question 18

Hok et al. (2016)

Answer 18

The increasing use of mice models in cognitive tasks that were originally designed for rats raises crucial questions about cross‐species comparison in the study of spatial cognition. The present review focuses on the major neuroethological differences existing between mice and rats, with particular attention given to the neurophysiological basis of space coding. While little difference is found in the basic properties of space representation in these two species, it appears that the stability of this representation changes more drastically over time in mice than in rats. We consider several hypotheses dealing with attentional, perceptual, and genetic aspects and offer some directions for future research that might help in deciphering hippocampal function in learning and memory processes.

Question 19

Egocentric v allocentric representations? Both exist in humans in some form (Nadel and Hardt, 2004; Burgess, 2006; Galati et al., 2010; Filimon, 2015)

Answer 19

• Widely suggested that humans and mammals have cog maps based allocentric representations in brain
• Many brain areas map spatial location of objects in egocentric reference frame (e.g. relative to eye, head/hand), e.g. in parieto-frontal cortex
• Could allocentric representations be explained via egocentric spatial reference frames?
• Potential allocentric task effects:
○ Mental shift of object to centre it frontally (egocentric left-right decisions)
○ Mental rotation
View-dependent object or scene recognition

see notes

Question 20

Nadal and Hardt (2004)

Answer 20

Themes emerging from the collection of articles in the Special Section on Long-Term Spatial Memory include the notion of multiple spatial systems, the relation between spatial representations and episodic memory, the role of context, and the neural systems involved in space. The authors conclude that distinguishing between egocentric and allocentric spatial systems makes sense of both behavioral and neurobiological data. The special role of the hippocampal system in allocentric space, and as a consequence, in context, suggests how a spatial system might end up central to the ability to remember episodes

Question 21

Burgess (2006)

Answer 21

Recent experiments indicate the need for revision of a model of spatial memory consisting of viewpoint-specific representations, egocentric spatial updating and a geometric module for reorientation. Instead, it appears that both egocentric and allocentric representations exist in parallel, and combine to support behavior according to the task. Current research indicates complementary roles for these representations, with increasing dependence on allocentric representations with the amount of movement between presentation and retrieval, the number of objects remembered, and the size, familiarity and intrinsic structure of the environment. Identifying the neuronal mechanisms and functional roles of each type of representation, and of their interactions, promises to provide a framework for investigation of the organization of human memory more generally.

Question 22

Galati et al. (2010)

Answer 22

We review human functional neuroimaging studies that have explicitly investigated the reference frames used in diVerent cortical regions for representing spatial locations of objects. Beyond the general distinction between “egocentric” and “allocentric” reference frames, we provide evidence for the selective involvement of the posterior parietal cortex and associated frontal regions in the speciWc process of egocentric localization of visual and somatosensory stimuli with respect to relevant body parts (“body referencing”). Similarly, parahippocampal and retrosplenial regions, together with speciWc parietal subregions such as the precuneus, are selectively involved in a speciWc form of allocentric representation in which object locations are encoded relative to enduring spatial features of a familiar environment (“environmental referencing”). We also present a novel functional magnetic resonance imaging study showing that these regions are selectively activated, whenever a purely perceptual spatial task involves an object which maintains a stable location in space during the whole experiment, irrespective of its perceptual features and its orienting value as a landmark. This eVect can be dissociated from the consequences of an explicit memory recall of landmark locations, a process that further engages the retrosplenial cortex.

Question 23

Filimon (2015)

Answer 23

The use and neural representation of egocentric spatial reference frames is well-documented. In contrast, whether the brain represents spatial relationships between objects inallocentric, object-centered, orworld-centeredcoordinates is debated. Here, I review behavioral, neuropsychological, neurophysiological (neuronal recording), and neuroimaging evidence for and against allocentric, object-centered, or world-centered spatial reference frames. Based on theoretical considerations, simulations, and empirical findings from spatial navigation, spatial judgments, and goal-directed movements, I suggest that all spatial representations may in fact be dependent on egocentric reference frames.

Question 24

Hippocampus lesions prior to training do not specifically impair WM or reference memory, but spatial task (Morris et al., 1982)

Answer 24

• All rats showed same escape latency in second phase of exp - cue-based navigation - reversal to hidden platform in 3rd phase - rats with hippocampal lesions perf poorly again
• Lesions after training have less strong effects - hippocampus is not the site for permanent memory storage but important in consolidation
Still perform well with cortical lesions - spatial task

see notes

Question 25

Hippocampus lesions prior to training do not specifically impair WM or reference memory, but spatial task (Morris et al., 1982) research

Answer 25

Clark et al. (2013)

Question 26

Morris et al. (1982)

Answer 26

Electrophysiological studies have shown that single cells in the hippocampus respond during spatial learning and exploration1–4, some firing only when animals enter specific and restricted areas of a familiar environment. Deficits in spatial learning and memory are found after lesions of the hippocampus and its extrinsic fibre connections5,6following damage to the medial septal nucleus which successfully disrupts the hippocampal theta rhythm7, and in senescent rats which also show a correlated reduction in synaptic enhancement on the perforant path input to the hippocampus8. We now report, using a novel behavioural procedure requiring search for a hidden goal, that, in addition to a spatial discrimination impairment, total hippocampal lesions also cause a profound and lasting placenavigational impairment that can be dissociated from correlated motor, motivational and reinforcement aspects of the procedure

Question 27

Clark et al. (2013)

Answer 27

Navigation depends on a network of neural systems that accurately monitor an animal’s spatial orientation in an environment. Within this navigation system are head direction (HD) cells which discharge as a function of an animal’s directional heading, providing an animal with a neural compass to guide ongoing spatial behavior. Experiments were designed to test this hypothesis by damaging the dorsal tegmental nucleus (DTN), a midbrain structure that plays a critical role in the generation of the rodent HD cell signal, and evaluating landmark based navigation using variants of the Morris water task. In Experiments 1 and 2, shams and DTN-lesioned rats were trained to navigate toward a cued platform in the presence of a constellation of distal landmarks located outside the pool. After reaching a training criteria, rats were tested in three probe trials in which (a) the cued platform was completely removed from the pool, (b) the pool was repositioned and the cued platform remained in the same absolute location with respect to distal landmarks, or (c) the pool was repositioned and the cued platform remained in the same relative location in the pool. In general, DTN-lesioned rats required more training trials to reach performance criterion, were less accurate to navigate to the platform position when it was removed, and navigated directly to the cued platform regardless of its position in the pool, indicating a general absence of control over navigation by distal landmarks. In Experiment 3, DTN and control rats were trained in directional and place navigation variants of the water task where the pool was repositioned for each training trial and a hidden platform was placed either in the same relative location (direction) in the pool or in the same absolute location (place) in the distal room reference frame. DTN-lesioned rats were initially impaired in the direction task, but ultimately performed as well as controls. In the place task, DTN-lesioned rats were severely impaired and displayed little evidence of improvement over the course of training. Together, these results support the conclusion that the DTN is required for accurate landmark navigation

Question 28

Place cells in the hippocampus: encoding of an observer-independent spatial location (O’Keefe and Dostrovsky, 1971)

Answer 28

• Popns of neurons (extracellular recordings in freely moving rats) with diff spatial prefs in hippocampus - collectively cells form spatial maps
- Defined by spatial layout

see notes

Question 29

Place cells in the hippocampus: encoding of an observer-independent spatial location (O’Keefe and Dostrovsky, 1971) research

Answer 29

Calton et al. (2003)

Question 30

O’Keefe and Dostrovsky (1971)

Answer 30

Responses of cells in the dorsal hippocampus of rats to restraining tactile stimuli as a function of spatial orientation suggest that the hippocampus provides the rest of the brain with a spatial reference map. The activity of cells in such a map would specify the direction in which the s was pointing relative to environmental landmarks and the occurrence of particular tactile, visual, etc., stimuli while facing in that orientation. It is hypothesized that activation of those cells specifying a particular orientation together with a signal indicating movement or intention to move in space would tend to activate cells specifying adjacent or subsequent spatial orientations. In this way, the map would “anticipate” the sensory stimuli consequent to a particular movement.

Question 31

Calton et al. (2003)

Answer 31

The occurrence of cells that encode spatial location (place cells) or head direction (HD cells) in the rat limbic system suggests that these cell types are important for spatial navigation. We sought to determine whether place fields of hippocampal CA1 place cells would be altered in animals receiving lesions of brain areas containing HD cells. Rats received bilateral lesions of anterodorsal thalamic nuclei (ADN), postsubiculum (PoS), or sham lesions, before place cell recording. Although place cells from lesioned animals did not differ from controls on many place-field characteristics, such as place-field size and infield firing rate, the signal was significantly degraded with respect to measures of outfield firing rate, spatial coherence, and information content. Surprisingly, place cells from lesioned animals were more likely modulated by the directional heading of the animal. Rotation of the landmark cue showed that place fields from PoS-lesioned animals were not controlled by the cue and shifted unpredictably between sessions. Although fields from ADN-lesioned animals tended to have less landmark control than fields from control animals, this impairment was mild compared with cells recorded from PoS-lesioned animals. Removal of the prominent visual cue also led to instability of place-field representations in PoS-lesioned, but not ADN-lesioned, animals. Together, these findings suggest that an intact HD system is not necessary for the maintenance of place fields, but lesions of brain areas that convey the HD signal can degrade this signal, and lesions of the PoS might lead to perceptual or mnemonic deficits, leading to place-field instability between sessions

Question 32

Place field maps: signal place recognition (Muller et al., 1987)

Answer 32

• Diff cells encode diff locations
• Shape and size of firing fields vary
• Not all complex spike cells act like place cells (D)
• In novel env pref can change
- Single cell can encode for diff spatial locations in diff contexts firing with varied patterns - may have diff patterns in same env (e.g. lights switched on/off)

see notes

Question 33

Place field maps: signal place recognition (Muller et al., 1987) research

Answer 33

Kinsky et al. (2018)

Question 34

Kinsky et al. (2018)

Answer 34

To provide a substrate for remembering where in space events have occurred, place cells must reliably encode the same positions across long time-scales. However, in many cases, place cells exhibit instability by randomly reorganizing their place fields between experiences, challenging this premise. Recent evidence suggests that, in some cases, instability could also arise from coherent rotations of place fields, as well as from random reorganization. To investigate this possibility, we performed in vivo calcium imaging in dorsal hippocampal region CA1 of freely moving mice while they explored two arenas with different geometry and visual cues across 8 days. The two arenas were rotated randomly between sessions and then connected, allowing us to probe how cue rotations, the integration of new information about the environment, and the passage of time concurrently influenced the spatial coherence of place fields. We found that spatially coherent rotations of place-field maps in the same arena predominated, persisting up to 6 days later, and that they frequently rotated in a manner that did not match that of the arena rotation. Furthermore, place-field maps were flexible, as mice frequently employed a similar, coherent configuration of place fields to represent each arena despite their differing geometry and eventual connection. These results highlight the ability of the hippocampus to retain consistent relationships between cells across long timescales and suggest that, in many cases, apparent instability might result from a coherent rotation of place fields

Question 35

Place cells rely on spatial information derived from idiothetic cues

Answer 35

• Vestibular activation (informs animal about own movements) and visual input from animal’s own movement modulate firing patterns of place cells
• Place cells continue firing in dark (e.g. when light off)
• O’Keefe and Speakman (1987) - after learning place cell fire according to correct choice (adequate response)/incorrect choices (inadequate responses)
- Eichenbaum et al. (1987) - rats trained to alternate turns - some place cells fired for location as expected, but other fired for location in conjunction with anticipation of left/right turn to be made - variation in place cells depending on whether going to make left or right turn

see notes

Question 36

Place cells rely on spatial information derived from idiothetic cues research

Answer 36

Eichenbaum et al. (1987)

Question 37

Eichenbaum et al. (1987)

Answer 37

Several techniques previously used to describe behavioral correlates of hippocampal unit and slow-wave activity are combined in a single odor- discrimination paradigm. Rats repetitively performed a sequence of behaviors during each trial: approach to a stimulus-sampling port, investigatory sniffing of the odor cue, orientation and approach toward a separate reward location, and water reward consumption. In a series of post hoc analyses, spike activity was time-locked to variations of each task event to uncover behavioral and physiological parameters that best synchronized unit firing. Three major categories of cells were identified: (1) “Cue-sampling” cells fired after onset of odor-cue sampling. Response magnitude was related to cue valence on both the current and past trials. (2) “Goal-approach” cells fired prior to arrival at either the odor-sampling port or reward cup. A number of sampling and approach cells also had place correlates. However, detailed analyses indicated that specific behaviors associated with increased firing reliably occurred at the same place. Unit activity was at least as well described by behavioral as spatial parameters. (3) “Theta” cells fired at high rates in strict relation to the ongoing limbic theta rhythm. This categorization suggests a functional organization of the hippocampus in which different cell types play complementary roles. Cue-sampling cells activated by discriminative stimuli during attentive fixations may be involved in comparing relative cue valence. Goal-approach cells may be involved in orientation movements for successive cue-sampling periods. Theta cells may provide synchronization of sensory acquisition during sampling, as well as in orientation movements during approach

Question 38

Head direction cells fire with directional preference maintained to familiar and novel envs

Answer 38

• Head direction cells are location-invariant
- Responses overlap strongly

see notes

Question 39

Head direction cells fire with directional preference maintained to familiar and novel envs research

Answer 39

Taube et al. (1996)

Question 40

Taube et al. (1996)

Answer 40

The strong signal carried byheaddirection cells in the postsubiculum complements the positional signal carried by hippocampal place cells; together, the directional and positional signals provide the information necessary to permit rats to generate and carry out intelligent, efficient solutions to spatial problems. Our opinion is that the hippocampal positional system acts as a cognitive map and that the role of the directional system is to put the map into register with the environment. In this way, paths found using the map can be properly executed.Headdirection cells have recently been discovered in parts of the thalamus reciprocally connected with the postsubiculum; such cells provide important clues to the organization of the directional system.

Question 41

Coding a representation of space (Moser and Moser, 2007)

Answer 41

see notes

• Fire whenever rats in location that has particular metric or relationship, so particular distance and direction
• Activity happens when rat not independent of how rat got from one location to another but when in location
• Similar to place
• Could argue that some of place cells map out space in some way
• Some mapping
• Grid cells less variable in responses - always respond in space that appears to map the actual layout of the space
- Less prone to variations in different contexts

• Taube (2006)

see notes

Head direction cells more distributed and across the brain

Question 42

Coding a representation of space (Moser and Moser, 2007) research

Answer 42

Taube (2007)

Question 43

Taube (2007)

Answer 43

Navigation first requires accurate perception of one’s spatial orientation within the environment, which consists of knowledge about location and directional heading. Cells within several limbic system areas of the mammalian brain discharge allocentrically as a function of the animal’s directional heading, independent of the animal’s location and ongoing behavior. These cells are referred to as head direction (HD) cells and are believed to encode the animal’s perceived directional heading with respect to its environment. Although HD cells are found in several areas, the principal circuit for generating this signal originates in the dorsal tegmental nucleus and projects serially, with some reciprocal connections, to the lateral mammillary nucleus → anterodorsal thalamus → PoS, and terminates in the entorhinal cortex. HD cells receive multimodal information about landmarks and self-generated movements. Vestibular information appears critical for generating the directional signal, but motor/proprioceptive and landmark information are important for updating it

Question 44

Golgi’s method of staining’s of neurons revolutionised the study of brains and neurons

Answer 44

• Hippocampal formation (medial temporal lobe): the dentate gyrus, the hippocampus proper (cornu ammonis), the subiculum (sometimes also included other adjacent areas of parahippocampal gyrus (e.g. presubiculum, parasubiculum, entorhinal cortex))
• Laminar structure and unidirectional connectivity (serial and parallel)
- Silver nitrate impregnation, Golgi (1843-1926) - seahorse in Greek:

see notes

Question 45

Golgi’s method of staining’s of neurons revolutionised the study of brains and neurons research

Answer 45

Vints et al. (2019)

Question 46

Vints et al. (2019)

Answer 46

Analysis of neuronal arborization and connections is a powerful tool in fundamental and clinical neuroscience. Changes in neuronal morphology are central to brain development and plasticity and are associated with numerous diseases. Golgi staining is a classical technique based on a deposition of metal precipitate in a random set of neurons. Despite their versatility, Golgi methods have limitations that largely precluded their use in advanced microscopy. We combined Golgi staining with fluorescent labeling and tissue clearing techniques in an Alzheimer’s disease model. We further applied 3D electron microscopy to visualize entire Golgi-stained neurons, while preserving ultrastructural details of stained cells, optimized Golgi staining for use with block-face scanning electron microscopy, and developed an algorithm for semi-automated neuronal tracing of cells displaying complex staining patterns. Our method will find use in fundamental neuroscience and the study of neuronal morphology in disease.

Question 47

Dentate gyrus filters incoming excitation from the entorhinal cortex (Lopez-Rojas and Kreutz, 2016)

Answer 47

• Classical trisynaptic hippocampal circuit model of info processing (Andersen et al., 1971)
- Also parallel connectivity: entorhinal cortex projections to both CA1 and CA3

see notes

Question 48

Dentate gyrus filters incoming excitation from the entorhinal cortex (Lopez-Rojas and Kreutz, 2016) research

Answer 48

The dentate gyrus is the main entrance of highly processed information to the hippocampus which derives from associative cortices and it is one of the few privileged areas in the brain where adult neurogenesis occurs. This creates the unique situation that neurons of diverse maturation stages are part of one neuronal network at any given point in life. While recently adult-born cells have a low induction threshold for long-term potentiation several studies suggest that following maturation granule cells are poorly excitable and they exhibit reduced Hebbian synaptic plasticity to an extent that it was even suggested that they functionally retire. Here, we review the functional properties of mature granule cells and discuss how plasticity of intrinsic excitability and alterations in excitation-inhibition balance might impact on their role in hippocampal information processing

Question 49

CA1-CA3 are major subdivisions in the hippocampus (Carew, 2000)

Answer 49

• CA - Cornu ammonis (Ammon’s horn), pyramidal cell layers
• Trisynaptic circuit:
1. Connection from entorhinal cortex to dentate granule cells via perforant path
2. Connection from granule cells to CA3 pyramidal cells via mossy fibres
3. Connection from CA3 pyramidal cells to CA1 pyramidal cells via Schaffer collaterals

see notes

Remarkably regular arrangement of soma and projections of principle neurons (pyramidal cells)

see notes

Can take slices from hippocampus that preserve a functioning network

see notes

Question 50

CA1-CA3 are major subdivisions in the hippocampus (Carew, 2000) research

Answer 50

Martin et al. (2019)

Question 51

Martin et al. (2019)

Answer 51

The hippocampus is not a unitary, homogeneous brain area. Anatomical and functional specialization is evident along the septotemporal axis of the structure, and between the left and right hemispheres. In the mouse brain, a left-right asymmetry has been discovered in the plasticity of CA3-CA1 projections originating in the left versus right hippocampus. Presynaptic afferents originating in the left hemisphere-including both uncrossed Schaffer collaterals, and crossed commissural projections to the contralateral CA1-form small, plastic synapses, whereas afferents originating in right CA3 contact larger, less plastic, synapses. Studies using optogenetic techniques to selectively activate fibers originating from one hemisphere in ex vivo slices have revealed that projections originating from left CA3 exhibit a far greater capacity for long-term potentiation (LTP) of synaptic strength than those originating on the right. However, corresponding data from rats are currently unavailable, leaving open the question of species differences in hippocampal symmetry. In the current study, we reanalyzed data from our previous in vivo LTP work to address this issue. We analyzed plasticity in independent Schaffer collateral and commissural projections to CA1 originating from left and right CA3 in male Lister-hooded rats. However, we found no differences in the magnitude and duration of LTP induced in either crossed or uncrossed pathways following high-frequency tetanization of left versus right CA3. This contrast with previous findings may stem from methodological differences between in vivo electrical and ex vivo optogenetic approaches, but may reflect a genuine species difference in the organization and laterality of the rodent CA3-CA1 system.

Question 52

Enhancement of synaptic transmission when both neurons fire

Answer 52

• LTP - LT potentiation
• Andersson (1966) found that in the perforant pathway of hippocampus of anesthetised rabbits that during repetitive stim an additional strong depolarisation with many fast pulses during few seconds (tetanus) caused increase in neuronal firing of post cell
· 0 = no change
• Bliss and Lømo (1973) continued work and discovered LTP demonstrating that freq potentiation’s can be long-lasting
• LTP found in other hippocampus pathways too
• LTP can last for hours - how?
- Changes induced post synaptically

see notes

Question 53

Enhancement of synaptic transmission when both neurons fire research

Answer 53

Martinez-Moreno et al. (2020)

Question 54

Martinez-Moreno et al. (2020)

Answer 54

Brain-derived neurotrophic factor (BDNF) is an essential product of protein synthesis with a prominent impact on brain signaling and synaptic plasticity. Exogenous application of this neurotrophin is able to inducelong-termpotentiation(LTP) in several brain structures such as the hippocampus along with increases in gene transcription and translation of proteins involved in functional and structural plasticity. In this regard, our previous studies have demonstrated that acute intrahippocampal administration of BDNF induceslong-lasting enhancement of synaptic transmission at the mossy fibers projection (MF) accompanied by a structural reorganization at the CA3 hippocampus area. Thus, considering the non-canonical molecular mechanisms underlying MF-CA3-LTP and the high expression of this neurotrophin in the CA3 area, we wonder whether transcriptional and translational inhibition interferes with the persistence of the MF functional and structural synaptic plasticity elicited by BDNF in adult rats in vivo. Our results show that BDNF is able to induce a lastingpotentiationof synaptic efficacy at the MF projection accompanied by a structural reorganization at the CA3 area in an mRNA synthesis and protein translation-independent manner. The present findings support the idea that BDNF is an essential plasticity related product, which is necessary and sufficient to induce and maintain functional and structural synaptic plasticity at the MF-CA3 pathway.

Question 55

NMDAR-dependent LTD and LTP in the hippocampus

Answer 55

A) Historical drawing by Cajal (1909) of trisynaptic pathway in hippocampus
· LTP and LTD induced by activation of NMDARs at synapses between CA3 and CA1 pyramidal neurons (blue and red)
· LTP at mossy fibre synapses onto CA3 neurons (green on blue) is NMDAR-independent
B) Electron microscopy image shows densely packed neuropil in CA1 region of hippocampus and highlights 2 asymmetric CA£-CA! synapses
· Typical ‘bouton en passant’ (buttons in passing) config of synapse 1 and prominent spine in synapse 2
· Post densities (PSDs) visible
C) Bidirectional change in CA3-CA1 synaptic efficiency by LTD and LTP in same synapses monitored by extracellular field recordings in acute slice prep of hippocampus
- Contrasting induction protocols

see notes

Question 56

NMDAR-dependent LTD and LTP in the hippocampus research

Answer 56

Luscher and Malenka (2012)

Question 57

Luscher and Malenka (2012)

Answer 57

Long-term potentiation and long-term depression (LTP/LTD) can be elicited by activatingN-methyl-D-aspartate (NMDA)-type glutamate receptors, typically by the coincident activity of pre- and postsynaptic neurons. The early phases of expression are mediated by a redistribution of AMPA-type glutamate receptors: More receptors are added to potentiate the synapse or receptors are removed to weaken synapses. With time, structural changes become apparent, which in general require the synthesis of new proteins. The investigation of the molecular and cellular mechanisms underlying these forms of synaptic plasticity has received much attention, because NMDA receptor–dependent LTP and LTD may constitute cellular substrates of learning and memory.

Question 58

Synaptic plasticity in the hippocampus (Nicoll et al., 1988)

Answer 58

Features of LTP: cooperativity, specificity, associativity

see notes

Question 59

Synaptic plasticity in the hippocampus (Nicoll et al., 1988) research

Answer 59

Zoladz et al. (2012)

Question 60

Zoladz et al. (2012)

Answer 60

We have studied the effects of spatial learning and predator stress‐induced amnesia on the expression of calcium/calmodulin‐dependent protein kinase II (CaMKII), brain‐derived neurotrophic factor (BDNF) and calcineurin in the hippocampus, basolateral amygdala (BLA), and medial prefrontal cortex (mPFC). Adult male rats were given a single training session in the radial‐arm water maze (RAWM) composed of 12 trials followed by a 30‐min delay period, during which rats were either returned to their home cages or given inescapable exposure to a cat. Immediately following the 30‐min delay period, the rats were given a single test trial in the RAWM to assess their memory for the hidden platform location. Under control (no stress) conditions, rats exhibited intact spatial memory and an increase in phosphorylated CaMKII (p‐CaMKII), total CaMKII, and BDNF in dorsal CA1. Under stress conditions, rats exhibited impaired spatial memory and a suppression of all measured markers of molecular plasticity in dorsal CA1. The molecular profiles observed in the BLA, mPFC, and ventral CA1 were markedly different from those observed in dorsal CA1. Stress exposure increased p‐CaMKII in the BLA, decreased p‐CaMKII in the mPFC, and had no effect on any of the markers of molecular plasticity in ventral CA1. These findings provide novel observations regarding rapidly induced changes in the expression of molecular plasticity in response to spatial learning, predator exposure, and stress‐induced amnesia in brainregions involved in different aspects of memory processing.

Question 61

Synapse in the rat’s CA1 region of the hippocampus (Lau and Zukin, 2007)

Answer 61

• Post membrane contains NMDA (N-Methyl-d-Aspartate), AMPA and mGlu (metabotropic glutamate receptors)
• NMDA receptor is tetrameric, glutamate-gated ion channel protein with variable subunits
- Scaffolding proteins connect NMDAR to signalling proteins

see notes

Question 62

Synapse in the rat’s CA1 region of the hippocampus (Lau and Zukin, 2007) research

Answer 62

Kennedy (2016)

Question 63

Lau and Kukin (2007)

Answer 63

• Synaptic NMDARs (N-methyl-D-aspartate receptors) and AMPARs (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors), two major classes of glutamate-gated ion channels, are localized to postsynaptic densities (PSDs) where they are structurally organized (and spatially restricted) in a large macromolecular signalling complex of scaffolding and adaptor proteins, which physically links the receptors to kinases, phosphatases and other downstream signalling proteins.
• NMDARs are synthesized and co-translationally assemble in the endoplasmic reticulum (ER) to form functional channels with differing physiological and pharmacological properties and distinct patterns of synaptic targeting. Nascent NMDARs are transported in vesicles with adaptor and scaffolding proteins by the kinesin motor KIF17 along microtubules in dendrites to synaptic sites.
• New research provides evidence that synaptic NMDAR number and subunit composition are not static, but change dynamically in a cell- and synapse-specific manner during development and in response to neuronal activity and sensory experience. Activity drives not only NMDAR synaptic targeting and incorporation, but also receptor retrieval, differential sorting of receptors into the endosomal–lysosomal pathway and lateral diffusion between synaptic and extrasynaptic sites.
• Homeostatic mechanisms limit NMDAR synaptic strength by regulating receptor number and phenotype at synaptic sites. Whereas activity blockade promotes alternative RNA splicing of the NR1 subunit and accelerates forward trafficking of NMDARs, chronic neuronal activity drives subunit-specific receptor internalization, intracellular sorting and protein degradation via the ubiquitin–proteasome system.
• Emerging evidence indicates that activity-dependent insertion and retrieval of NMDARs to and from synaptic sites mediates some forms of long-term potentiation (LTP) and long-term depression (LTD), cellular processes that are widely believed to be involved in learning and memory, as well as metaplasticity at central synapses.
- Dysregulation of NMDAR trafficking may have a role in the behavioural symptoms associated with neuropsychiatric disorders such as cocaine addiction, chronic alcohol abuse, schizophrenia and Alzheimer’s disease

Question 64

Kennedy (2016)

Answer 64

Learning and memory require the formation of new neural networks in the brain. A key mechanism underlying this process is synaptic plasticity at excitatory synapses, which connect neurons into networks. Excitatory synaptic transmission happens when glutamate, the excitatory neurotransmitter, activates receptors on the postsynaptic neuron. Synaptic plasticity is a higher-level process in which the strength of excitatory synapses is altered in response to the pattern of activity at the synapse. It is initiated in the postsynaptic compartment, where the precise pattern of influx of calcium through activated glutamate receptors leads either to the addition of new receptors and enlargement of the synapse (long-term potentiation) or the removal of receptors and shrinkage of the synapse (long-term depression). Calcium/calmodulin-regulated enzymes and small GTPases collaborate to control this highly tuned mechanism.

Question 65

Roles of the NMDA and AMPA receptors in the induction of LTP in the CA1 region

Answer 65

• APV (/AP5 2R)-amino-5-phosphonovaleric acid) is NMDA receptor antagonist
• Glutamate sufficiently concentrated - 2 conditions required to activate - glutamate needs to bind to NMDA and EPSP dislodges magnesium ion that blocks receptor - depolarises PS membrane
- NMDA receptor = coincidence detector

see notes

Question 66

Roles of the NMDA and AMPA receptors in the induction of LTP in the CA1 region research

Answer 66

Alkondon et al. (2003)

Question 67

Alkondon et al. (2003)

Answer 67

In the hippocampus, glutamatergic inputs to pyramidal neurons and interneurons are modulated by alpha7* and alpha3beta4* nicotinic acetylcholine receptors (nAChRs), respectively, present in glutamatergic neurons. This study examines how nicotinic AMPA, and NMDA receptor nAChR activities are integrated to regulate the excitability of CA1 stratum radiatum (SR) interneurons in rat hippocampal slices. At resting membrane potentials and in the presence of extracellular Mg2+ ( 1 mM), nicotinic agonists triggered in SR interneurons excitatory postsynaptic currents (EPSCs) that had two components: one mediated by AMPA receptors, and the other by NMDA receptors. As previously shown, nicotinic agonist - triggered EPSCs resulted from glutamate released by activation of alpha3beta4* nAChRs in glutamatergic neurons/fibers synapsing directly onto the neurons under study. The finding that CNQX caused more inhibition of nicotinic agonist - triggered EPSCs than expected from the blockade of postsynaptic AMPA receptors indicated that this nicotinic response also depended on the AMPA receptor activity in the glutamatergic neurons synapsing onto the interneuron under study. Nicotinic agonists always triggered action potentials in CA1 SR interneurons. In most interneurons, these action potentials resulted from activation of somatodendritic AMPA receptors and alpha7* nAChRs. In interneurons expressing somatodendritic alpha4beta2* nAChRs, activation of these receptors caused sufficient membrane depolarization to remove the Mg2+-induced block of somatodendritic NMDA receptors; in these neurons, nicotinic agonist - triggered action potentials were partially dependent on NMDA receptor activation. Removing extracellular Mg2+ or clamping the neuron at positive membrane potentials revealed the existence of a tonic NMDA current in SR interneurons that was unaffected by nAChR activation or inhibition. Thus integration of the activities of nAChRs, NMDA, and AMPA receptors in different compartments of CA1 neurons contributes to the excitability of CA1 SR interneurons.

Question 68

Steps in the neurochemical cascade during the induction of LTP

Answer 68

see notes

Question 69

Does hippocampal LTP have anything to do with spatial learning? (Morris et al., 1986)

Answer 69

• APV - NMDA blocker
• 8 days training with hidden platform
• Day 9 - test without platform
• Some APV treatment also suppressed LTP
- Cannot learn the task 

see notes

Question 70

Does hippocampal LTP have anything to do with spatial learning? (Morris et al., 1986) research

Answer 70

This paper reports a series of three experiments that tested the “spatial-mapping” and “working-memory” theories of hippocampal function. The experimental designs incorporate separate reference- and working-memory procedures of a water-escape task, using both spatial and non-spatial learning. In Experiment 1 (Reference memory), rats with hippocampal (HC) or cortical (CC) lesions and unoperated (UNOP) rats learned to swim to a rigid visible escape platform while avoiding contact with a floating one. In the nonspatial task, the platforms each occupied any of 8 possible positions in the pool over successive trials but differed in appearance. In the spatial task, the platforms were of identical appearance but the safe one always occupied a single fixed location. The HC rats showed a highly specific spatial learning impairment but did learn to perform consistently above chance towards the end of training. In Experiment 2 (working memory), new groups of rats were trained on similar spatial and nonspatial tasks, but the platform designated correct-in terms of its visual appearance or its spatial location-was randomly changed each day. No animal learned the nonspatial task despite extensive training. Performance on the spatial version unexpectedly revealed an impairment in the CC as well as the HC group relative to the UNOP rats. However, the HCs again performed at above chance levels and demonstrated rapid (I-trial) spatial learning towards the end training. Experiment 3 used a place navigation matching-to-sample task examine spatial working memory further. Each day, an underwater platform was hidden at any of 4 possible locations, and the rats were given 2 trials to search for it. Both UNOP and CC rats located the platform faster on Trial 2 than on Trial 1, even when the inter-trial interval was long as 30min. HC rats were no faster on Trial 2 than on Trial 1. We conclude that hippocampal lesions (1) severely but partially impair spatial but not visual reference memory and (2) give rise to different patterns impairment in different working-mermory tasks. The results are a challenge to both the spatial-mapping and working-memory theories.

Question 71

Targeting the NMDA receptor with genetic tools (Tsien et al., 1996)

Answer 71

LTP normal in wild-type animals and controls (genetically engineered), but absent in NMDA knockouts

see notes

Question 72

Targeting the NMDA receptor with genetic tools (Tsien et al., 1996) research

Answer 72

Using the phage P1–derivedCre/loxPrecombination system, we have developed a method to create mice in which the deletion (knockout) of virtually any gene of interest is restricted to a subregion or a specific cell type in the brain such as thepyramidal cellsof thehippocampal CA1 region. TheCre/loxPrecombination–basedgene deletionappears to require a certain level ofCre proteinexpression. The brain subregional restrictedgene knockoutshould allow a more precise analysis of the impact of agene mutationon animal behaviors.

Question 73

Spatial learning in birds (Reiner, 2009)

Answer 73

Hippocampus involved in spatial orientation and learning in birds

see notes

Question 74

Spatial learning in birds (Reiner, 2009) research

Answer 74

The study of birds, especially the Galapagos finches, was important to Darwin in the development of the theory of evolution by natural selection. Birds have also been at the centre of a recent reformulation in understanding cerebral evolution and the substrates for higher cognition. While it was once thought that birds possess a simple cerebrum and were thus limited to instinctive behaviours, it is now clear that birds possess a well-developed cerebrum that looks very different from the mammalian cerebrum but can support a cognitive ability that for some avian species rivals that in primates

Question 75

Larger hippocampus found in food storers and nest parasites (Healy et al., 2005)

Answer 75

• Female cowbirds also perf better than males in DMTS spatial memory task (Guigeuno et al., 2014)
- Can be linked to sex-specific development and behav repertoire required to successfully locate nests for eggs

see notes

Question 76

Larger hippocampus found in food storers and nest parasites (Healy et al., 2005) research

Answer 76

Behavioural ecology assumes that cognitive traits and their underlying neural substrates are shaped by natural selection in much the same way as morphological traits are, resulting in adaptation to the natural environment of the species concerned. Recently, however, the ‘neuroecology’ approach of attempting to gain insight into brain structure and function by testing predictions about variation in brain structure based on knowledge of the lifestyle of the animal has been criticized on the grounds that such an adaptationist view cannot provide insight into the underlying mechanisms. Furthermore, the criticism has focussed on attempts to use variation in demand for spatial memory and in hippocampal size as a basis for predicting variation in cognitive abilities. Here, we revisit this critique against the field of so-called ‘neuroecology’ and argue that using knowledge of the natural history of animals has lead to a better understanding of the interspecific variation in spatial abilities and hippocampal size, and to the generation of novel hypotheses and predictions.

Question 77

Tackling researcher bias: sex differences in human behaviour and cognition are small but important (Nori et al., 2018)

Answer 77

• Researcher bias can lead to limitations in Qs and approaches but also to overinflated claims and wrongly extrapolate findings to whole popns

• E.g. biomedical research still carried out largely on male subjects (rats, mice, men; Choleris et al., 2018)
• Gender similarities hyp: ‘males and females are similar on most, but not all, psych variables’ (Hyde, 2005)

see notes

Question 78

Tackling researcher bias: sex differences in human behaviour and cognition are small but important (Nori et al., 2018) research

Answer 78

Choleris et al. (2018)

Hyde (2005)

Hyde (2016

Question 79

Nori et al. (2018)

Answer 79

The present study has two-fold aims: to investigate whether gender differences persist even when more time is given to acquire spatial information; to assess the gender effect when the retrieval phase requires recalling the pathway from the same or a different reference perspective (egocentric or allocentric). Specifically, we analyse the performance of men and women while learning a path from a map or by observing an experimenter in a real environment. We then asked them to reproduce the learned path using the same reference system (map learning vs. map retrieval or real environment learning vs. real environment retrieval) or using a different reference system (map learning vs. real environment retrieval or vice versa). The results showed that gender differences were not present in the retrieval phase when women have the necessary time to acquire spatial information. Moreover, using the egocentric coordinates (both in the learning and retrieval phase) proved easier than the other conditions, whereas learning through allocentric coordinates and then retrieving the environmental information using egocentric coordinates proved to be the most difficult. Results showed that by manipulating familiarity, gender differences disappear, or are attenuated in all conditions.

Question 80

Choleris et al. (2018)

Answer 80

Biological differences between males and females are found at multiple levels. However, females have too often been under-represented in behavioral neuroscience research, which has stymied the study of potential sex differences in neurobiology and behavior. This review focuses on the study of sex differences in the neurobiology of social behavior, memory, emotions, and recovery from brain injury, with particular emphasis on the role of estrogens in regulating forebrain function. This work, presented by the authors at the 2016 meeting of the International Behavioral Neuroscience Society, emphasizes varying approaches from several mammalian species in which sex differences have not only been documented, but also become the focus of efforts to understand the mechanistic basis underlying them. This information may provide readers with useful experimental tools to successfully address recently introduced regulations by granting agencies that either require (e.g. the National Institutes of Health in the United States and the Canadian Institutes of Health Research in Canada) or recommend (e.g. Horizon 2020 in Europe) the inclusion of both sexes in biomedical research

Question 81

Hyde (2005)

Answer 81

The differences model, which argues that males and females are vastly different psychologically, dominates the popular media. Here, the author advances a very different view, the gender similarities hypothesis, which holds that males and females are similar on most, but not all, psychological variables. Results from a review of 46 meta-analyses support the gender similarities hypothesis. Gender differences can vary substantially in magnitude at different ages and depend on the context in which measurement occurs. Overinflated claims of gender differences carry substantial costs in areas such as the workplace and relationships

Question 82

Hyde (2016)

Answer 82

Gender stereotypes hold that males outperform females in mathematics and spatial tests, and females outperform males on verbal tests. According to meta-analyses, however, among both children and adults, females perform equally to males on mathematics assessments. The gender difference in verbal skills is small and varies depending on the type of skill assessed (e.g., vocabulary, essay writing). The gender difference in 3D mental rotation shows a moderate advantage for males, but this gender difference occurs in the absence of a spatial curriculum in the schools. Meta-analyses of gender differences across a wide array of psychological qualities support the Gender Similarities Hypothesis, which states that males and females are quite similar on most—but not all—psychological variables.

Question 83

summary

Answer 83

• Spatial info imp for behav
• Animals can find and learn routes and rely on egocentric reference frames
• Some animals (birds travelling over long distances, mice) and humans have been shown to form allocentric representations too
• Hippocampus of major imp for spatial learning and navigation in vertebrates
• LTP at specific synapses between 3 pathways of hippocampus mediate spatial learning
• Blocking NMDA receptors prevents LTP and spatial learning providing evidence for causal link
• Species and indv diffs might be intuitive and therefore easy to explain but may not always hold true with further exp scrutiny
- Awareness of researcher and confirmation bias and diversity and inclusivity in research teams and institutions are imp factors for successful advancement of scientific knowledge