Lectures 10-12 Flashcards

Question

Explain Eichenbaum's "Memory Space" hypothesis and how it reconceptualises hippocampal function beyond spatial mapping.

Answer 1

The hippocampus creates a multidimensional framework that organises memory through three principles: Sequential encoding: It represents experiences as ordered sequences of events and places. Each hippocampal cell encodes a segment containing stimuli, actions and spatial context, structuring experiences in time. Relational linking: It links episodes by shared features like events or locations. Some cells code unique combinations; others respond to common elements, forming associations across experiences. Flexible network construction: It builds a relational network that allows flexible recall and novel inferences. This lets us navigate conceptual spaces similarly to physical ones. This model extends the hippocampus’s role beyond spatial mapping by: • Explaining how it supports both navigation and abstract thought • Showing why damage disrupts relational but not direct memory • Supporting inference and recombination of memory elements • Unifying spatial and non-spatial memory in one system The hypothesis reframes the hippocampus as a multidimensional map of experience, not just of space.

Answer 2

Eichenbaum's recordings revealed multiple response patterns: * Odour cells (place-independent) - fired selectively to specific odours regardless of location * Place cells (odour-independent) - fired at specific locations regardless of odour * Match/mismatch cells - responded based on whether current trial matched previous trial * Combination cells - fired to specific combinations of location, odour and match/mismatch status * About 65% of hippocampal neurons responded to one or more task variables, with most cells responding to combinations of factors. This shows the hippocampus creates integrated representations of multiple memory dimensions beyond just spatial mapping.

Answer 3

METHODS: Rats were trained on a hierarchical odor preference task (A>B>C>D>E) with overlapping odor pairs. After training, selective lesions were performed on either: * Fornix (hippocampal output pathway) *Parahippocampal region (PHR; perirhinal + entorhinal cortices) Performance was tested on three distinct trial types to dissociate memory functions. RESULTS: Both fornix-lesioned and PHR-lesioned rats showed: * Normal performance (~75-80% correct) on directly trained premise pairs (BC+CD) * Perfect performance (~100% correct) on end-anchored pairs (AE) * Severely impaired performance (at chance level, ~50%) on BD probe trials requiring transitive inference This double dissociation demonstrates that: * The hippocampal system is specifically required for inferential relationships between separately learned memories * Direct associations can be formed and maintained without hippocampal involvement * The critical function of the hippocampus is organising relationships between memories rather than storing individual memories themselves The anatomical circuit (cortex → parahippocampal region → hippocampus → back to cortex) forms an integrated system where disruption at any point specifically impairs relational processing while preserving simpler forms of memory.

Answer 4

An auto-associative network features recurrent connections that feed back to the same neurons that initiated firing. This network architecture is primarily implemented in the dentate gyrus of the hippocampus. Auto-associative networks are specialized for pattern completion, allowing complete memories to be retrieved from partial inputs. They enable pattern separation, the process of distinguishing similar experiences as distinct neural representations. These networks are limited to single item/pattern retrieval rather than processing sequential information.

Answer 5

A hetero-associative network features unidirectional connections between different neuronal populations. This network architecture is primarily implemented in the CA3 region of the hippocampus. In hetero-associative networks, activated neurons trigger firing of subsequent elements in a sequence, but not previous ones. They are specialized for sequential memory processing and the temporal organization of information. These networks support memory for ordered events in episodic memories, enabling forward-directed memory retrieval.

Answer 6

The dentate gyrus performs pattern separation through sparse coding, distinguishing similar inputs. The CA3 region implements both network types through its unique connectivity patterns. Auto-associative properties support pattern completion, retrieving complete memories from partial cues. Hetero-associative properties enable sequential processing, maintaining temporal relationships between events. This dual architecture allows the hippocampus to distinguish between similar experiences while preserving their relationships. The complementary networks enable both retrieval of discrete memory elements and their sequential organization. This integrated system provides the neural basis for organizing memories in a relational "memory space" as proposed by Eichenbaum.

Answer 7

Vertical firing patterns represent individual memory elements (items) that are encoded and retrieved rapidly. These item-specific patterns show repeated activation across the same cells when processing single components of a memory. Horizontal firing patterns stretch across multiple cells and represent the complete sequential memory. The horizontal patterns operate on a slower timescale than vertical patterns, reflecting the additional time needed to process relationships between elements. This temporal organization creates a matrix where: * Fast vertical processing = individual items/elements * Slow horizontal processing = complete sequential memories This dual temporal structure enables the hippocampus to simultaneously maintain both discrete elements and their sequential relationships within a memory.

Answer 8

Rapid temporal processing (vertical patterns) allows quick recognition and retrieval of individual memory elements. Slower temporal processing (horizontal patterns) enables the integration of elements into coherent sequential memories. The interaction between fast and slow processing creates a hierarchical memory structure. This temporal hierarchy supports both pattern completion of individual elements and sequential organization of complete memories. The different timescales allow the hippocampus to efficiently process both the content of memories (what) and their temporal structure (when).

Answer 9

Pattern completion is the ability to reconstruct a complete memory from partial or degraded input. For example, when you see part of a familiar room, you can recall the entire layout and contents. This process occurs primarily in the CA3 region through auto-associative networks. When a subset of neurons representing part of a memory is activated, recurrent connections enable the network to activate the full ensemble of neurons associated with the complete memory. Pattern completion is crucial for memory retrieval in real-world conditions where cues are often incomplete or ambiguous.

Answer 10

Pattern separation is the process of transforming similar inputs into distinct, non-overlapping neural representations. For example, being able to form separate memories of two different birthday parties despite their similar features. This process occurs primarily in the dentate gyrus through sparse coding. The dentate gyrus has many more neurons than its input region (entorhinal cortex), allowing similar input patterns to be distributed across different neural populations. Pattern separation is crucial for reducing interference between similar memories and maintaining distinct episodic memories. Without effective pattern separation, similar experiences would overwrite each other, leading to confusion and memory interference.

Answer 11

Theta oscillations (slow) structure the temporal framework of memory, segmenting sequences of items across time. Gamma oscillations (fast) nest within theta cycles, allowing multiple discrete items (e.g. A→D) to be encoded within a single theta cycle. Each gamma sub-cycle represents a distinct item, enabling serial encoding via phase coding. This nested architecture supports item separation and temporal ordering, essential for episodic memory. Physiologically, this aligns with hippocampal field potentials showing gamma bursts nested within theta rhythms during sequential memory tasks.

Answer 12

Within each theta cycle (4–10 Hz), multiple gamma cycles (30–80 Hz) occur, each encoding a distinct memory item via synchronous firing of specific pyramidal neuron ensembles. Empirical estimates suggest ~7 ± 2 gamma cycles per theta wave, matching the classic STM capacity (Ebbinghaus). Each gamma sub-cycle represents a different network state (e.g., item A–G), enabling sequential activation and temporal ordering.

Answer 13

As a rat moves through a place field, hippocampal place cells fire at progressively earlier phases of the theta cycle, a phenomenon known as phase precession. Firing is strongest near the theta trough, corresponding to the centre of the place field. This shifting phase code allows position to be encoded relative to theta rhythm, creating a temporal code for spatial information. Because the task is simple and repetitive, noise is low, revealing consistent theta-linked firing patterns.

Answer 14

Theta phase precession is the progressive shift in place cell firing to earlier phases of the theta cycle as an animal moves through a place field. Initially, spikes occur at late (positive) phases; as the animal progresses, spikes advance to earlier phases. This creates a temporal code for position: the theta phase of firing correlates with spatial location. It allows the hippocampus to compress sequences of locations into a single theta cycle - supporting spatial and episodic memory encoding. Demonstrated by O’Keefe & Recce (1993) in rats running linear tracks.

Answer 15

As a rat moves through overlapping place fields (e.g., P1 → P5), each place cell fires at a specific location and progressively earlier theta phases. At any point (e.g., X), several place cells fire simultaneously - strongest from the peak field (e.g., P2), weaker from adjacent fields (e.g., P1, P3). This overlapping activity forms a population code for location and direction. The theta phase of each cell’s firing adds a temporal dimension, helping to encode position within a trajectory. Thus, spatial and temporal information are jointly encoded by hippocampal cell assemblies.

Answer 16

Place cells fire near the trough of the theta cycle and show phase precession (earlier firing with movement through the field). Across multiple cells, these theta-timed spikes form ordered sequences representing spatial positions. Each gamma cycle (~30–80 Hz) within a theta wave (~4–10 Hz) encodes one item (e.g., location A, B, C), creating a temporal sequence of positions. Overlaying cell activity reveals a compressed representation of past, current and future locations within a single theta cycle. This theta-gamma code enables animals to maintain an internal spatial map and plan navigational trajectories.

Answer 17

Place cells fire at gamma frequency (~7 ± 2 events) nested within a theta rhythm (4–10 Hz). Firing is paced by theta: Past positions are encoded by cells firing at late theta phase, the current position by those firing at the theta trough, future locations by cells firing at early theta phase. For example, as the animal moves through place field P3, that cell fires: * First at late theta (coming from P2), * Then strongest at the trough (P3 centre), * Then early theta (heading toward P4/P5). This creates a temporally compressed sequence (past → present → future) within a single theta cycle, with each item encoded in its own gamma sub-cycle. This structure allows: * Prediction of upcoming locations. * Encoding of trajectory and episodic information. * Integration of space and time within hippocampal circuits. The system links neural dynamics (theta-gamma coupling) with cognitive capacity (memory, navigation, planning).

Answer 18

METHODS: * Participants are shown a sequence of digits (e.g., 1–6), followed by a delay. * A probe digit is then presented. * Task: Decide if the probe was part of the original list. * Mean reaction time (RT) is recorded for each memory load (1–6 items). RESULTS: * RT increases linearly with number of items, regardless of whether the answer is yes or no. * Slope ≈ 38 ms per item, consistent with ~30 Hz gamma frequency. * Suggests a serial scanning process: one item compared per gamma cycle (not parallel - searching all at once). * Theta rhythm paces these gamma comparisons, aligning with hippocampal models of memory encoding. * Supports the idea that memory retrieval involves gamma-paced serial search, even in humans, where direct recording is limited.

Answer 19

METHODS: * Human participants performed a Sternberg task (1, 3, 5, or 7 digits). * A sensory control task used crosses instead of digits. * MEG recorded cortical activity during the retention interval from 61 locations. RESULTS: * Theta power (4-8 Hz) was greater during STM tasks vs. sensory control (digits > crosses). * Theta power increased with memory load, peaking around 7 items, matching STM capacity. * Power plateaued when STM load saturated, suggesting a capacity-linked oscillatory mechanism. * Supports theory that theta paces gamma, with each gamma cycle indexing an item in memory. * Aligns with behavioural slope from Sternberg (~30 Hz = gamma frequency), indicating serial memory scanning.

Answer 20

High theta-gamma coupling (TGC): * Strong gamma activity represents individual items. * Each item is consistently locked to distinct phases of theta. * This supports accurate temporal ordering of events (e.g., L → A → K → M). * Results in good memory encoding and precise recall. Low TGC: * Weak gamma activity leads to degraded item representation. * Poor phase alignment with theta disrupts event ordering. * Results in inaccurate recall (e.g., scrambled sequence A → L → K → M). TGC enables theta phase to structure memory temporally, and gamma cycles to encode discrete items. Without this synchronisation, memory suffers, highlighting the importance of oscillatory coordination in episodic memory.

Answer 21

METHODS: * EEG recorded from 64 channels during 0-, 1-, and 2-back tasks. * Compared performance across HC, MCI, and AD groups. * Focused on theta-gamma coupling (TGC) rather than just band power. RESULTS: * TGC was the best predictor of 2-back task accuracy, across all clinical groups. * TGC strength correlated with correct performance (targets > non-targets). * TGC remained predictive regardless of diagnosis — MCI and AD both showed impaired TGC and reduced accuracy. * TGC was not predictive in non-ordering tasks, supporting its specific role in temporal working memory. Conclusion: TGC reflects dynamic item-order binding in working memory. Its disruption in MCI/AD highlights its potential as a biomarker for early cognitive decline.

Answer 22

It's the memory for a behavioural output that we train. They are not fixed; they continue to be modified by experience and tuned by repetition. It's related to how the motor cortex communicates to the striatum and cerebellum.

Answer 23

These two types of memory rely on different, but partially overlapping, brain circuits. 1. The acquisition of habits and skills 2. Sensory-to-motor-adaptations, involving the adaptation of reflexes. (AKA Conditioning). E.g., Given something light, at the next presentation you will prepare to hold something light. When it's actually heavy, at the next presentation you will prepare for something heavy.

Answer 24

Primary Motor Cortex: - The top level of these motor circuits, critical for the control of force and the flow in muscle movements. Premotor Cortex: - Involved in movement preparation and sequencing; co-ordination of muscle on either side of the body

Answer 25

Primary Motor Cortex Premotor Cortex Supplementary Motor Cortex Cerebellum Striatum

Answer 26

Cerebellum role is to send error message back, monitoring the movement based on the cortical plan, it will communicate the discrepancy due to errors to help correct.

Answer 27

Striatum (Caudate + putamen) Cerebellum https://imagekit.io/tools/asset-public-link?detail=%7B%22name%22%3A%22screenshot_1745074305179.png%22%2C%22type%22%3A%22image%2Fpng%22%2C%22signedurl_expire%22%3A%222028-04-18T14%3A51%3A45.672Z%22%2C%22signedUrl%22%3A%22https%3A%2F%2Fmedia-hosting.imagekit.io%2F7a6fa3dc8ecd4c20%2Fscreenshot_1745074305179.png%3FExpires%3D1839682306%26Key-Pair-Id%3DK2ZIVPTIP2VGHC%26Signature%3DR1QPJIlyfljHQCIQEvqOlV4Yj2np3FT2UP1R783wOASPh9i03EP3FIVrPCEBfG9lxX7wUcySjYxY8f8wHNYNZjjbzVuvSYYg5Zcf~CC~F6ykMC9OaTwq8vZVWqWUthyL4PDQoi0dODvMTFjYQxvn9fuiBHI3TIaaGLe0ZeNjVMgsXALcfRuVod8MgHhBbDb0RfirhvavBJ4FIae3UjWzLmKyy8frgKtGcbhNFe1ugeDHb3gPTiRUCBwcJ3Wd3rgBUvVLWQIQJ~SPu0ZSal14Zt2O2NHQycgossXDP3rfvR02-WduuGlfKqMREifL03LawtKM~7XBvYz3daeV5RXWHg__%22%7D

Answer 28

In water maze experiments, striatal and hippocampal systems show specialised roles in learning: * Visual discrimination task (colour-based): Striatal lesions cause severe impairment while hippocampal-lesioned animals perform like controls. * Spatial discrimination task (position-based): Hippocampal/fornix lesions cause severe impairment while striatal-lesioned animals perform like controls. This double dissociation demonstrates that the striatal system is critical for stimulus-response learning (procedural memory), while the hippocampal system is essential for spatial learning (declarative memory).

Answer 29

Striatal-lesioned animals show: * Severe impairment in visual discrimination tasks where learning depends on association between a specific stimulus (colour) and reward * Persistent high error rates across training trials when discriminating by colour cues * Intact performance in spatial discrimination tasks where position, not stimulus features, predicts reward * These deficits reflect the striatum's crucial role in habit formation and procedural memory acquisition.

Answer 30

METHODS: * Water maze containing two visually discriminable floating rubber balls * One ball positioned above large escape platform (+), one above too-small platform (-) * Visual Discrimination Variant: Position of platforms varied; animals must discriminate by COLOUR * Spatial Discrimination Variant: Escape platform position constant; colours varied randomly * Three experimental groups: control, striatal lesion and fornix/hippocampal lesion animals RESULTS: * Visual Discrimination (colour-based): Striatal-lesioned animals showed persistent impairment (high error rates) across all trial blocks; control and hippocampal groups improved steadily * Spatial Discrimination (position-based): Hippocampal/fornix-lesioned animals showed severe impairment; control and striatal groups learned effectively * Double dissociation demonstrated between striatal (stimulus-response) and hippocampal (spatial) learning systems

Answer 31

METHODS: * Water maze with two differently colored floating balls * Position of platforms varied across trials * Animals required to discriminate by COLOUR to find escape platform * Success required learning stimulus-response association (colour → escape) * Performance measured by mean number of errors across 15 trial blocks RESULTS: * Control animals: Showed steady learning curve with decreasing errors * Fornix/hippocampal animals: Performed similarly to controls * Striatal-lesioned animals: Showed severe impairment with consistently high error rates * By final trials, ~4-error difference between striatal and other groups * Demonstrated striatum's critical role in non-spatial, cue-based learning

Answer 32

METHODS: * Water maze with two floating balls of different colors * Escape platform position remained constant across trials * Colour of balls varied (no longer associated with escape) * Animals required to discriminate by POSITION to find escape * Performance measured across 7 trial blocks RESULTS: * Control animals: Showed effective learning with errors decreasing to near-zero * Striatal-lesioned animals: Performed similarly to controls, reaching low error rates * Fornix/hippocampal animals: Showed persistent impairment with higher error rates * By final trials, ~3-error difference between hippocampal and other groups * Confirmed hippocampus/fornix is essential for spatial learning independent of visual cues

Answer 33

METHODS: * Rats trained on both place tasks and response tasks until proficient * Striatal (caudate) lesions performed after training * Testing conducted post-lesion to assess retention * Place tasks: standard 8-arm radial maze and place memory task * Response tasks: "turn right into adjacent arm" and right-left discrimination ("take left arm of two available") * Performance measured pre-lesion and post-lesion RESULTS: * Place tasks: Normal performance maintained after striatal lesions (~80% correct) * Response tasks: Performance dropped to chance level after lesions (~30-40% correct) * Double dissociation demonstrated between intact spatial memory and impaired procedural/habit memory * Confirmed striatum's selective role in response learning but not spatial learning

Answer 34

METHODS: * Two response tasks tested: * "Turn right into adjacent arm" task requiring egocentric response * Right-left discrimination task ("take left arm of two available") * Pre-lesion performance at ~100% correct * Post-lesion performance compared to chance level RESULTS: * Post-lesion performance dropped to chance level (~30-40% correct) * Adjacent arm task: Rats unable to consistently execute the learned "turn right" response * Right-left discrimination: Rats unable to maintain the learned habit of selecting left arm * Demonstrated striatum's critical role in procedural memory and stimulus-response associations * Indicated that striatal lesions specifically impair habitual behaviors rather than spatial navigation

Answer 35

METHODS: * Monkeys trained to fixate central point, then follow sequence of three dots (L, R, or U positions) * Animals required to fixate each location in presentation order before reaching to target * Six different sequence combinations tested (LUR, RLU, URL, LRU, ULR, RUL) * Single-unit recordings from striatal neurons during task performance RESULTS: * Striatal neurons showed sequence-specific activation patterns * Neurons responded to particular locations only within specific sequence contexts * Example: Neuron fired strongly for "L" position only in ULR pattern, not in other sequences * Demonstrated context-dependent coding where neural response depends on sequence position * Supported striatum's role in encoding procedural aspects of sequential motor behaviors

Answer 36

Context-dependent coding refers to striatal neurons that respond to specific actions only when they occur within particular sequential contexts. In Kermadi & Joseph's study, neurons fired for a location (e.g., "L") only when it appeared in a specific sequence (e.g., ULR). This property is significant because it: * Explains how the striatum encodes complex action sequences, not just individual movements * Provides neural basis for procedural memory's sequence-specific nature * Demonstrates how habits become "chunked" into integrated behavioral units * Explains why striatal damage impairs sequence learning while preserving individual movements * Reveals how the brain transitions from conscious sequence execution to automatic performance

Answer 37

Water Maze Discrimination: * Striatum essential for visual/cue-based discrimination (colour → reward) * Striatal lesions impair stimulus-response learning but spare spatial learning * Demonstrates striatum's role in simple associative learning 8-Arm Radial Maze (Cook & Kesner): * Striatal lesions impair response tasks ("turn right," "choose left arm") * Spatial navigation remains intact after striatal lesions * Shows striatum's role in egocentric response learning Sequence Learning (Kermadi & Joseph): * Striatal neurons encode actions in sequence-specific contexts * Neurons respond to locations only within particular sequences * Reveals striatum's role in complex procedural learning and action sequencing All paradigms demonstrate striatum's critical role in procedural/habit learning while confirming its non-involvement in spatial/declarative memory.

Answer 38

The striatum facilitates procedural learning through: * Initial encoding of stimulus-response associations in dorsomedial striatum * Gradual shift to dorsolateral striatum as behaviors become habitual * Context-dependent neuronal firing that encodes specific action sequences * Integration with cortical inputs to form stable motor programs * Dopaminergic reinforcement that strengthens successful action patterns This organisation enables the transition from conscious, goal-directed actions to automatic, efficient habits, allowing complex behaviours to be executed with minimal cognitive load.

Answer 39

The double dissociation reveals: * Brain contains parallel, specialised learning systems that operate simultaneously * Striatal system: Processes stimulus-response associations and procedural sequences * Hippocampal system: Processes spatial relationships and declarative knowledge * Systems can compete or cooperate depending on task demands * Damage to one system may unmask the operation of the other * Evolution has preserved these distinct systems because they serve complementary functions in learning * Explains why certain memory functions remain intact after brain damage while others are impaired

Answer 40

Striatal neurons support sequence learning through: * Pattern-specific firing that responds to actions only in specific sequential contexts * Integration of cortical inputs from motor, sensory and prefrontal regions * Medium spiny neurons that require coordinated input to become active * Synaptic plasticity that strengthens connections between neurons representing sequential actions * Lateral inhibition that suppresses competing motor programs * Sustained activity patterns that bridge temporal gaps between sequence elements * Dopamine-mediated reinforcement that stabilizes successful action chains These properties create a neural substrate for encoding complex procedural memories as unified action sequences.

Answer 41

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Answer 42

The striatum receives projections from the entire cortex. It has minimal projections to the brainstem and none to the spinal cord. The striatum primarily projects to the thalamus. The thalamus then projects to premotor, motor and prefrontal cortex. This forms a cortex → striatum → thalamus → cortex loop. This connectivity allows integration of diverse information without direct motor control.

Answer 43

The striatum lacks direct projections to the spinal cord. It influences movement selection through the thalamo-cortical pathway. This indirect control allows modulation of which actions are selected. The architecture explains why striatal damage impairs action selection but not basic movement. It enables the striatum to function as a "gatekeeper" for learned procedural responses.

Answer 44

The striatum receives input from the entire cortex, enabling context-action associations. The striatum-thalamus-cortex loop creates a circuit strengthened through repetition. Limited output pathways force selection between competing actions. The loop architecture allows learned sequences to trigger automatically. This organisation enables complex behaviors to execute without conscious control.

Answer 45

METHODS: * Rats trained to run T-maze for food reinforcement * Auditory cues (click/tone) signaled turn direction * Four learning stages with 40 trials per session: * Acquisition (sessions 1-5): learn to 72% correct * Overtraining (sessions 6-15): strengthen habit * Extinction (sessions 16-22): no/little reinforcement * Reacquisition (sessions 23-28): reinforcement restored * Striatal neural activity recorded throughout RESULTS: * Performance improved during acquisition/overtraining (80-85% correct) * Performance dropped during extinction (to near 0%) * Rapid recovery during reacquisition (to 90%+) * Running time decreased with learning, increased during extinction * Trial duration showed similar pattern

Answer 46

Striatal neurons show distinct activity patterns across learning stages. During acquisition, neural activity gradually increases as associations form. In overtraining, activity stabilises as the behaviour becomes habitual. During extinction, striatal activity patterns become disrupted. Reacquisition shows rapid restoration of striatal firing patterns. The striatum encodes the relationship between cues and appropriate motor responses. This pattern demonstrates the striatum's role in forming and maintaining procedural memories.

Answer 47

Extinction causes performance to drop dramatically (near 0% correct). Running time increases substantially during extinction. Despite performance loss, reacquisition occurs rapidly. This rapid reacquisition suggests procedural memories remain stored during extinction. The striatum maintains the learned associations even when not expressed. This differs from declarative memory which shows gradual relearning curves. The pattern demonstrates that habits, once formed, are difficult to erase completely. Procedural memory shows "savings" - faster relearning than original acquisition.

Answer 48

METHODS: * Researchers recorded striatal neuron activity across T-maze task phases * Neural activity visualized as heat map (red/orange = high firing, blue = low firing) * Activity measured during overtraining (session 11) and extinction (session 23) RESULTS: * Striatal neurons show phase-specific activation patterns during task execution * Strongest activity (red/orange clusters) occurs during turn onset/offset phases * Neural activity patterns correlate directly with behavioural performance * Spike proportion increases during acquisition/overtraining, decreases in extinction * Warning cue neural response strongly predicts both accuracy and speed * Different task components are encoded by specific striatal neuron populations

Answer 49

The warning cue response in striatal neurons serves as a critical predictor of performance. Higher neural activity during warning cue strongly correlates with percentage correct (r ≈ 0.8). Warning cue response negatively correlates with running time (stronger signal = faster performance). This preparatory activity represents the activation of the learned procedural memory. The warning cue response demonstrates how the striatum initiates learned action sequences. This early neural activity provides evidence for the striatum's role in action preparation. The correlation with performance metrics confirms the functional significance of this neural encoding.

Answer 50

Striatal neural activity shows systematic changes across learning stages. During acquisition, spike proportion gradually increases as the task is learned. In overtraining, activity reaches peak levels with strongest encoding during turn execution. During extinction, neural activity patterns significantly decrease, particularly in turn-related phases. In reacquisition, activity patterns rapidly recover to levels similar to overtraining. These changes directly parallel behavioral performance metrics. The pattern demonstrates how procedural memories are encoded, suppressed, and reactivated in striatal circuits. The rapid recovery during reacquisition provides neural evidence for the persistence of procedural memories.

Answer 51

* During acquisition, novel task‑related ensembles form and stabilise. * In extinction, these patterns reverse and then re‑emerge. * On re‑acquisition, the original ensembles are reinstated—changes tightly track behavioural performance.

Answer 52

* Acquisition: non‑task‑related spikes are actively suppressed. * Extinction: these irrelevant spikes rebound. * Re‑acquisition: suppression of irrelevant firing resumes alongside task‑relevant pattern reinstatement.

Answer 53

They are the neural equivalents of habit learning: specific, task‑phase‑locked ensembles in cortex→striatum→substantia nigra pathways encode automated response strategies.

Answer 54

Early trials depend on hippocampal spatial mapping; with training, control transfers to the dorsolateral striatum, where select output neurone ensembles (not global striatal activation) encode the habitual turn‑response.

Answer 55

Anatomically, the striatum sends no direct projections to spinal motor neurones; instead, it projects to pallidal and nigral output nuclei, modulating thalamo‑cortical circuits rather than driving muscles itself.

Answer 56

Reciprocal links between striatum and motor/premotor cortices support the planning, sequencing and initiation of complex movement patterns, by selecting and reinforcing cortical motor programmes.

Answer 57

Afferents from the amygdala convey motivational/emotional salience, while PFC inputs provide executive planning; integration within the striatum enables action selection aligned with reward expectations and behavioural goals.

Answer 58

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Answer 59

* Afferents: direct proprioceptive input from the spinal cord plus bi‑directional connections with brainstem nuclei (vestibular, reticular, red nuclei) and descending “efference copy” from motor cortex. * Efferents: cerebello‑thalamo‑cortical projections (smaller in magnitude than striatal outputs) to premotor and primary motor cortices for adjusting motor commands.

Answer 60

* Receives intended movement plan (from motor cortex) and actual sensory feedback (spinal/brainstem). * Integrates these to detect discrepancies (prediction vs. outcome). * Sends corrective signals via the thalamus back to motor/premotor cortex to refine ongoing and future motor commands.

Answer 61

Bi‑directional loops with brainstem (e.g. vestibular, reticular) link spinal reflex arcs and cerebellar computation, allowing immediate modulation of muscle tone and posture in response to changing sensory inputs.

Answer 62

* Projection strength: cerebellar outputs to cortex are comparatively small; striatal outputs are more extensive. * Function: cerebellum specialises in real‑time error correction and sensorimotor integration; striatum underpins goal‑directed action selection and habitual sequence encoding.

Answer 63

This region has much stronger connections with the brain stem and spinal cord and much weaker connections to the cortex than the striatal circuit. This suggest that it's circuitry may be more involved in execution of movements and the acquisition of conditioned reflexes.

Answer 64

CS: Tone or light lasting 250–1 000 ms US: Corneal air‑puff to the eyelid UR: Reflexive eyeblink to the air‑puff CR: Learned eyeblink in response to the CS alone after several CS–US pairings

Answer 65

Interpositus lesion or protein synthesis blockade within it prevents animals ever acquiring a CR Neither manipulation alters the reflexive UR, proving interpositus is critical for learning but not for basic blink circuitry

Answer 66

During training: inactivating red nucleus or its projection from interpositus blocks CR expression On recovery: CRs emerge immediately at their learned magnitude, showing learning occurred “offline” even though performance was suppressed during inactivation

Answer 67

METHODS: * Paired a tone/light CS (250–1 000 ms) with a corneal air‑puff US in rabbits, measuring reflexive UR and learned CR. * Lesioned or blocked protein synthesis in the interpositus nucleus to test acquisition. * Reversibly inactivated the red nucleus (and its projection from interpositus) during training to dissociate learning versus performance. RESULTS: * Interpositus lesions or protein synthesis blockade abolished CR acquisition but left the UR intact. * Red‑nucleus inactivation prevented CR expression during training, yet on recovery rabbits immediately expressed CRs at full strength, demonstrating that learning was stored in the interpositus nucleus independent of real‑time output.

Answer 68

A wide range of observable behaviours, expressed *feelings* and changes in body state.

Answer 69

1. Feelings 2. Actions 3. Physiological Arousal (e.g., autonomic arousal) 4. Motivational Programs (adaptive programs that solve problems)

Answer 70

Joy/Sadness Affection/Disgust Anger/Fear Expectation/Surprise

Answer 71

A set of interconnected subcortical and cortical structures (centred on the hypothalamus) that mediate emotion, stress responses, mood regulation and reward/addiction processes.

Answer 72

Hippocampus → fornix → mammillary bodies → mammillothalamic tract → anterior thalamic nuclei → cingulate cortex → entorhinal cortex → hippocampus; proposed to underlie emotional expression.

Answer 73

Inclusion of amygdala, septal area, nucleus accumbens and portions of prefrontal cortex, forming the “paleomammalian” brain layer for integrating emotion with cognition and drive.

Answer 74

Brain comprises: reptilian (brainstem/basal ganglia), paleomammalian (limbic), neomammalian (neocortex); limbic system evolved to add emotional and motivational regulation atop primitive motor/drive circuits. * Debunked as it's based on birds; it's a vast underestimation of what birds and lizards can do, it's largely false.

Answer 75

Its central role in emotion, stress and reward makes it vulnerable in mood and psychotic disorders; therapeutics modulate noradrenaline, dopamine and serotonin transmission within limbic circuits.

Answer 76

Morphology: * From rabbit→cat→monkey, neocortex shows progressive gyrencephaly (degree of cortical folding) and relative expansion, whereas limbic structures stay proportionally constant. Implication: * Advanced mammals possess greater neocortical real‑estate for high‑order processing (e.g. context, planning), while phylogenetically older limbic circuits continue to mediate conserved emotional drives.

Answer 77

Expanded neocortex, particularly prefrontal regions, sends descending projections to amygdala, hypothalamus and brainstem, exerting top‑down inhibitory control over limbic‑driven responses and facilitating deliberate reappraisal.

Answer 78

* Classical conditioning: Automatic affective reactions (e.g. fear, pleasure) acquired via subcortical loops (Papez/MacLean circuits) in the limbic system. * Cognitive appraisal: Context‑sensitive evaluation and regulation of the same stimuli by neocortical networks (especially prefrontal cortex), enabling flexible, goal‑directed emotional control.

Answer 79

They removed the cortex in cats and dogs which produced an aggressive reaction (sham rage) to routine handling. Suggests that the cortex controls (inhbits) the expression of emotional responses.

Answer 80

Following the discovery of decortication rage when cortex was removed, he went on to show that subcortical sites (particularly the hypothalamus) are particularly important in emotions such as sham rage.

Answer 81

Sensory input → thalamus “Stream of feeling”: thalamus → hypothalamus (mammillary bodies) → anterior thalamic nuclei via mammillothalamic tract “Brain reaction”: anterior thalamus → cingulate gyrus → sensory neocortex (produces conscious feeling) “Stream of thought”: cingulate → hippocampus via cingulum → hypothalamus via fornix Autonomic output: hypothalamus → brainstem/spinal autonomic centres → physiological expression (mood)

Answer 82

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Answer 83

Feeling (“brain reaction”): cingulate gyrus and associated neocortical areas Physiological expression (“body reaction”): hypothalamus via autonomic outputs from thalamus Debate: whether bodily changes (autonomic arousal) precede and generate conscious feeling (James–Lange), or vice versa (Cannon–Bard)

Answer 84

Sensory afferents (e.g. visual, auditory) arrive at thalamus for rapid arousal Memory/contextual inputs to cingulate/hippocampus supply past experience Integration within the loop links external stimuli with past emotional associations, coordinating feeling (cingulate) and physiological response (hypothalamus) into a coherent mood.

Answer 85

* Anatomical vagueness: Includes heterogeneous nuclei (hippocampus, amygdala, septum, PFC) with diverse functions beyond emotion. * Overlap with other systems: Many so‑called limbic regions participate in memory, attention, motor control and cognition. * Distributed dynamics: Emotional states arise from temporally coordinated activity across multiple large‑scale circuits (cortical and subcortical), not a single “on/off” limbic toggle. * Whole‑brain integration: Modern imaging and connectivity studies show emotion emerges from network interactions spanning neocortex, basal ganglia, cerebellum and brainstem as well as traditional limbic nodes.

Answer 86

Components: * Papez circuit (hippocampus, fornix, mammillary bodies, anterior thalamus, cingulate cortex) * Broca’s limbic lobe (pyriform & rhinal cortices) * Septum & portions of basal ganglia * Amygdala, ventromedial PFC & orbitofrontal cortex (later additions) Function: Integrates visceral (internal) states with sensory inputs to generate adaptive visceromotor and affective responses—i.e. the “visceral brain” for emotion and drive.

Answer 87

* Provides the sole direct sensory input to allocortex (olfactory cortex) without thalamic relay. * Phylogenetically the oldest major sense, especially pronounced in macrosmatic mammals for detecting environmental cues.

Answer 88

* A collection of nuclei in the anterior temporal lobes, continuous with the caudate. * Electrical stimulation elicits fear and rage in animals. * Integrates with cingulate cortex to mediate emotional valence and emotional memory consolidation.

Answer 89

* Critical for autobiographical (episodic) and contextual memory. * Encodes the context in which fearful or emotional events occur, providing situational framework for amygdala‑driven fear responses.

Answer 90

* Coordinates autonomic responses (e.g. sympathetic activation during fear) via descending projections to brainstem and spinal centres. * Regulates endocrine systems through pituitary control (e.g. stress hormone release), integrating emotional and physiological homeostasis.

Answer 91

The amygdala sits in the anterior medial temporal lobe, immediately above the parahippocampal gyrus and adjacent to the hippocampus. It lies ventral to the anterior nucleus of the thalamus and cingulate gyrus, and rostral to the mammillary bodies, with the fornix arching just above it.

Answer 92

Afferents: * Olfactory bulb via lateral olfactory tract * Sensory thalamus (via dorsomedial nucleus) and sensory cortices (e.g. temporal areas) * Hippocampus/parahippocampal gyrus (contextual input) Efferents: * Stria terminalis → hypothalamus (mammillary bodies) & septal nuclei * Ventral amygdalofugal pathway → basal forebrain nuclei, anterior thalamus, and cingulate gyrus * Outputs to brainstem autonomic centres for emotional‐behavioural responses

Answer 93

Lateral nucleus (L): main sensory‑integration hub, receives thalamic & cortical inputs. Basal nuclei (B; including basolateral & basomedial complexes): further integrate L outputs, modulate reward/emotional valence. Centro‑medial nuclei (C‑M): final output stage projecting to hypothalamus, brainstem and striatum to drive autonomic and behavioural responses.

Answer 94

Site of CS–US plasticity in fear conditioning (tone/light ↔ shock). Receives rapid “low road” thalamic input for coarse threat detection and “high road” cortical input for detailed evaluation. Sends processed signals to basal and C‑M nuclei and to hippocampus for contextual modulation.

Answer 95

Basolateral nucleus (BLa/BLp): promotes reward‑seeking, suppresses social approach and can be anxiogenic; projects to nucleus accumbens and PFC. Basomedial nucleus: exerts anxiolytic influence, regulating stress resilience via connections back to hippocampus and hypothalamus.

Answer 96

* Receive convergent input from lateral & basal nuclei. * Project to hypothalamic (autonomic/endocrine) and brainstem motor centres to produce fear‑related arousal (↑heart rate, sweating, freezing) and hormonal release.

Answer 97

METHODS: * Extracellular single‑unit recordings from basolateral amygdala in awake macaques. * Presented photographs of four familiar monkeys each displaying three facial expressions (appeasement/lip‑smack, neutral, threat). * Collected peristimulus time rasters and firing‑rate histograms for each identity–expression combination. RESULTS: * Many neurons (≈ 64 %) exhibited non‑linear tuning: their firing depended on a specific identity‑expression pairing, not on expression or identity alone. * Examples included cells that responded most to appeasement in one monkey but not to threat or neutral, and others preferring threat > neutral > appeasement. * Demonstrates basolateral amygdala encodes high‑order, context‑dependent social signals rather than simple feature detection.

Answer 98

“Low‑road” thalamic route: Sensory organ → sensory thalamus → lateral nucleus of amygdala (rapid, coarse) “High‑road” cortical route: Sensory organ → sensory cortex → lateral nucleus (detailed, slow) Contextual inputs: Hippocampus → basal and lateral nuclei (provides spatial/episodic context)

Answer 99

The hippocampus encodes the environmental context of an aversive event and sends this information to the amygdala’s lateral and basal nuclei. This contextual signal allows the amygdala to generate fear responses selectively in the original conditioning environment.

Answer 100

Central grey (periaqueductal grey): orchestrates defensive behaviours (freezing, fight/flight) Lateral hypothalamus: triggers autonomic outputs (↑heart rate, blood pressure, respiration) Bed nucleus of the stria terminalis: drives neuroendocrine hormone release (stress hormones via HPA axis)

Answer 101

Detection: Threat → sensory organ Relay: → thalamus (“low road”) and → sensory cortex (“high road”) Integration: → amygdala (lateral → basal/accessory basal → central nucleus), with contextual gating by hippocampus Output: central nucleus → brainstem/autonomic/endocrine centres → coordinated emotional behaviour, autonomic arousal and hormonal responses.

Answer 102

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Answer 103

CS → LA: * Thalamic “low road”: auditory thalamus → LA (fast, coarse) * Cortical “high road”: auditory cortex → LA (slower, detailed) US → LA: * Thalamic: somatosensory thalamus → LA * Cortical: somatosensory cortex → LA LA → CE: integration of CS–US associations CE outputs: * Central grey (periaqueductal grey): freezing * Lateral hypothalamus: blood‐pressure increase * Paraventricular nucleus (PVN) of hypothalamus: stress‐hormone release

Answer 104

They provide a rapid, subcortical shortcut for coarse sensory information to reach the amygdala, enabling immediate defensive reactions before slower cortical processing refines stimulus evaluation.

Answer 105

METHODS: * Conditioning: Paired an auditory CS (tone) with a footshock US in one environment. * Testing: Measured freezing to (a) the original context and (b) the tone in a novel context. * Lesions: Bilateral lesions of amygdala (lateral/central nuclei), hippocampus or dorsal striatum. RESULTS: * Amygdala lesions: abolished freezing to both context and tone (disrupts Pavlovian and contextual conditioning). * Hippocampal lesions: selectively eliminated contextual freezing but left tone‑elicited freezing intact. * Striatal lesions: had no effect on either form of fear conditioning.

Answer 106

METHODS: Subjects: Rats implanted with tetrodes in lateral amygdala (LA). Procedures: * Baseline: 10 tone CS presentations (no US). * Conditioning: 10 tone CS–footshock US pairings. * Controls: unpaired CS/US (to test necessity of pairing). * Differential conditioning: interleaved CS⁺ (paired) vs CS⁻ (unpaired). * Extinction: repeated CS alone. Measurements: peristimulus spike rasters & firing‐rate histograms for each trial block. RESULTS: * Conditioning: All recorded LA neurons showed a marked increase (>200 %) in CS‐evoked firing after CS–US pairing (Quirk et al., 1997). * Unpaired control: No change in CS responses when CS and US were unpaired (Quirk et al., 1995). * Differential: CS⁺ responses potentiated; CS⁻ responses actually depressed below baseline. * Extinction: CS‐elicited firing declined in concert with behavioural extinction, indicating a new inhibitory memory trace (CS ≠ US) that suppresses but does not erase the original CS→US association.

Answer 107

Before conditioning: LA neurons show minimal or inconsistent tone‐evoked spiking. After paired CS–US conditioning: All recorded LA units exhibit a robust increase in tone‐evoked firing (>200 % of baseline) across 10 CS–US pairings (Quirk et al., 1997). Control (unpaired CS/US): When tone and shock are presented unpaired, LA responses to the tone do not change, proving that CS–US contingency is required for synaptic plasticity.

Answer 108

Novel context or CS-: LA neurons do not increase firing to a novel tone or in a familiar tone presented in a non‑shock context, mirroring absence of freezing. CS⁺ with CE inactivation: Infusing lidocaine into central nucleus (CE) blocks freezing but does not prevent the conditioned increase in LA firing to CS⁺. Conclusion: LA stores the CS→US memory trace; behavioural output (freezing) is downstream in CE.

Answer 109

CS⁺ (paired): Tone‐evoked LA firing potentiates markedly. CS⁻ (unpaired): Tone‐evoked firing actually depresses below pre‐training baseline. Implication: LA circuits can encode positive (potentiation) and negative (depression) valence based on CS–US contingency.

Answer 110

During extinction (CS alone): CS‐evoked LA firing gradually declines in parallel with reductions in freezing. Memory trace: Original CS→US potentiation is not erased but inhibited - LA units remain capable of firing if inhibition is lifted. Inference: Extinction forms a new inhibitory memory (CS ≠ US) rather than unlearning the original association.

Answer 111

Infralimbic (IL) PFC→LA projections: IL activation during extinction drives GABAergic interneurons in LA, suppressing CS‐evoked firing. Functional role: This top‑down inhibition gates the expression of the original fear memory without erasing it, enabling context‑dependent retrieval of extinction.

Answer 112

METHODS: * Rats underwent tone–shock conditioning (Day 1), followed by extinction training (tone alone) later that day. * On Day 2, before testing, half received bilateral ventromedial PFC (vmPFC) lesions; controls had sham surgery. * Measured freezing to the tone during Day 2 recall. RESULTS: * Conditioning & extinction (Day 1): vmPFC‑lesioned and sham groups froze similarly during tone–shock pairing and showed equivalent extinction. * Recall (Day 2): Sham rats exhibited low freezing (extinction recall), whereas vmPFC‑lesioned rats showed high freezing—failure to recall extinction. * Conclusion: vmPFC is not required for initial extinction learning but is essential for retrieval of the extinction memory.

Answer 113

METHODS: * Rats implanted with electrodes in infralimbic (IL) cortex. * Underwent tone–shock conditioning, extinction training (tone alone) on Day 1, and extinction recall (tone alone) on Day 2. * Recorded IL neuronal firing and measured freezing. RESULTS: * Extinction recall (Day 2): A subpopulation of IL neurons showed a significant increase in tone‑evoked firing only during recall, coinciding with reduced freezing. * Interpretation: IL neuronal activity signals the retrieval of extinction memory and likely exerts top‑down inhibition over amygdala to suppress fear responses. * Clinical note: Impaired IL activation during extinction recall is implicated in PTSD and anxiety disorders.

Answer 114

Tulving (1983, 2002) as being a memory specific to humans that receives and stores information about temporally dated episodes or events and the temporal-spatial relationships between them.

Answer 115

It's memory for 'what', 'where' and 'when', learnt in a single 'trial' requiring no 'training'. It includes the ability to plan for future events (mental time travel).

Answer 116

METHODS: * Birds learned that wax worms perish 124 h after caching, whereas peanuts remain fresh. * Caching 1: Each jay cached either peanuts or worms on one half of a tray for 4 h. * Caching 2 (120 h later): Jays cached the other food type on the opposite tray half. * Retrieval test (after removing food): Presented empty tray with fresh sand at either 4 h or 124 h post‑worm caching. * Controls: (a) Jays never taught worm decay (tested at 4 h vs 124 h); (b) decay timing reversed. RESULTS: * At 4 h, jays preferentially inspected/recached worm sites (worms still edible). * At 124 h, jays ignored worm sites and inspected peanut sites instead (worms decayed). * In untaught controls, jays inspected worm sites equally at both intervals, ruling out simple forgetting. * Conclusion: Jays remember what was cached, where, and when, meeting Tulving’s episodic‐memory criteria.

Answer 117

METHODS: * Over 6 days, jays experienced a rotating schedule: * “Breakfast compartment” (A or C) delivered food in the morning; the other compartment was empty. * Each location alternated daily in a counterbalanced order. * On Day 7, jays were sated, then given pine nuts and access to both compartments (no food bowls). * Measured where jays chose to cache nuts (anticipating next‑day breakfast). RESULTS: * Jays cached significantly more nuts in the compartment that had been empty at that time of day during training. * Demonstrates planning for a future state (hunger) by choosing a location where food would be needed. * Caveat: Repeated training introduces associative reinforcement; without verbal report, true “episodic” or “mental time‐travel” interpretations remain debated.

Answer 118

WWWWhen: Episodic memory requires encoding What happened, Where, and When (Tulving). Animal issue: “When” (temporal order or elapsed time) is hard to demonstrate non‑verbally and often confounded by circadian or age cues.

Answer 119

WWWWhich: Substitutes “when” with identification of the experience context (“which occasion”/which session). Eacott & Easton (2010): Rats can remember which of two encoding episodes an object–location event occurred, demonstrating a contextual, single‑trial memory dependent on hippocampus.

Answer 120

Incidental encoding: Animals aren’t reinforced or trained to memorize; memory forms spontaneously. Single‑trial learning: One exposure suffices to test real‑time episodic encoding. WWWWhich elements: Must test what (item), where (location) and which occasion (context A vs B). Hippocampal dependency: Impairment by medial temporal lesions confirms reliance on classic episodic‑memory circuitry.

Answer 121

Encode “Which” & “What–Where”: In Context A (grey walls), rats explore two novel objects (e.g. cube & cylinder) at fixed locations. Encode alternative “Which”: In Context B (grid walls), same objects appear but swapped locations. Test “Which” recall: After a delay, rats return to Context A and encounter two identical copies of one object (e.g. two cubes). Preferential exploration of the copy in the location never occupied by that object in Context A indicates recall of the object–place–context pairing.

Answer 122

Persistence: Rats show significant novel‐location exploration (exploration score > 0) up to 60 min after encoding; performance falls to chance by 120 min. Measure: Exploration preference = (time on novel object–location) − (time on familiar), plotted against log‑delay. A positive score indicates intact episodic‑like memory.

Answer 123

WWWWhich memory: Fornix lesions abolish the exploration preference at both 2 min and 5 min delays (performance at chance), confirming hippocampal dependency. Object–location control: The same lesions do not impair standard What–Where memory (novel‐location preference for a novel object shape), indicating that contextual “Which” recall uniquely requires hippocampal circuits. (Requires EC)

Answer 124

* Perirhinal cortex: encodes What (object identity) * Hippocampus: encodes Where (object location) * Postrhinal cortex: encodes Which (context/occasion) Integration: The hippocampus binds object–place–context into a unified What–Where–Which representation; fornix lesions abolish this combined memory while sparing individual components.

Answer 125

Early onset: Deficit emerges at the same prodromal stage as in humans - before overt amyloid/tau pathology. Progressive worsening: Memory impairment intensifies as Alzheimer‑like pathology advances. Age-related decline in controls: Wild‑type mice show a parallel, milder decline in WWWWhich performance with normal ageing.

Answer 126

Prevalence: ~500 000 affected, ≈ 60 % of UK dementia cases. Stages: * Mild cognitive impairment (MCI): prodromal AD * Early AD * Mid‑stage AD * Late/end‑stage AD

Answer 127

Earliest symptoms: Impaired episodic memory acquisition (difficulty forming new episodic memories) and spatial/navigation deficits. Spared system early on: Familiarity‑based or perceptual memory can remain intact.

Answer 128

Deficits in executive functions - such as planning, cognitive flexibility and inhibitory control - typically appear in mid to late stages of AD.

Answer 129

APP_SWE (Swedish mutation): drives overproduction of amyloid‑β. PS1_M146V (Presenilin‑1): enhances γ‑secretase processing of APP, increasing Aβ42. Tau_P301L: induces tau hyperphosphorylation and neurofibrillary tangles (frontotemporal‑dementia mutation), without which tangles do not form.

Answer 130

4 months: Onset of spatial memory and synaptic‑plasticity impairments. 10–12 months: Appearance of extracellular amyloid‑β plaques in hippocampus and cortex. ~15 months: Development of intracellular phosphorylated‑tau neurofibrillary tangles.

Answer 131

Because it reproduces the key stages of human AD - early synaptic/spatial deficits, followed by progressive Aβ plaque and tau tangle pathology - providing a temporal window to test whether episodic‑like (What–Where–Which) memory declines in parallel with disease markers.

Answer 132

A fixed circular/elliptical “virtual zone” is drawn around each object. Exploration time is counted whenever the mouse’s nose/head enters that zone (angle irrelevant). Zone size is held constant across NOR, OLT, What–Which, WWWWhich and W–W–When tasks.

Answer 133

D= (T novel − T familiar)/Total Exploration * D > 0 → novelty preference * D < 0 → familiarity preference * D = 0 → no preference (“chance”)

Answer 134

What → Perirhinal cortex Where → Hippocampus Which → Postrhinal cortex What–Where–Which → Hippocampus (integrates all three)

Answer 135

It appears by 6 mo - before overt Aβ plaques and tau tangles - mirroring prodromal episodic‑memory loss (MCI) in humans, while single‑component familiarity (recency) remains intact.

Answer 136

METHODS: One‑component: * Novel Object Recognition (NOR): tests What (object identity). * Object Location Task (OLT): tests Where (spatial location). Two‑component: * What–Where: same object moved to a new place—tests binding of What+Where. * What–Which: same object presented in a novel context - tests binding of What+Which (context). Three‑component (WWWWhich): * Combines object, place and context in a single trial- tests What+Where+Which binding. RESULTS: * NOR → perirhinal cortex * OLT → hippocampus * What–Where → hippocampus * What–Which → postrhinal cortex * WWWWhich → hippocampal integration of all three

Answer 137

METHODS: * NOR: 3 min exposure to two identical objects → 2 min delay → 3 min test with one novel object. * OLT: same timing; one object displaced in test. RESULTS: * NOR: both genotypes D≈0.18 (novelty preference), no difference → intact object identity memory. * OLT: controls D≈0.24 (p<0.05); 3×TgAD D≈0.12 (p≈0.05), significantly lower than controls → spatial memory present but impaired.

Answer 138

METHODS: * 3 min in Context A with Object A. * 3 min in Context B with the same Object A. * 2 min delay. * 3 min test in Context B with two copies of Object A—one congruent, one novel context pairing. RESULTS: * Both 3×TgAD and controls show D≈0.25 (p<0.01), with no genotype difference → intact object–context binding.

Answer 139

METHODS: * Rats sample two objects in Context 1 and two in Context 2 (3 min each). * Delays of 2, 5, 10, 15, 30 min (3 min tests). * D‑scores averaged over 2–15 min delays per age. RESULTS: * 3 mo: both genotypes D>0 (p<0.001) → intact episodic‐like memory * 6 mo: controls D≈0.17 (p<0.001), 3×TgAD D≈0 (ns) → deficit emerges * 12 mo: controls D≈0.08 (p<0.05), 3×TgAD D<0 (ns) → persistent impairment

Answer 140

METHODS: * 5 min Acq1 with Object A + Object ★ (“old”). * 5 min Acq2 with Object B + Object □ (“recent”). * 2 min delay. * 5 min test with all four objects arranged so only Object A is both old & displaced. RESULTS: * Both genotypes preferentially explore the Displaced‑Old object (D>0, p<0.01) → intact recency/place binding even at 14 mo.

Answer 141

METHODS: * Transgenic for APP_SWE, PS1_M146V, Tau_P301L. * Longitudinal histology and behaviour. RESULTS: * 4 mo: synaptic‐plasticity & spatial deficits appear. * 10–12 mo: extracellular amyloid‑β plaques in hippocampus & cortex. * ~15 mo: intracellular phosphorylated‑tau tangles. * Aligns with gradual emergence of episodic‐like memory deficits in these mice.

Answer 142

Standard Consolidation Theory (SCT) – hippocampus is essential for recent episodic memories but not for remote memories once they’ve been fully transferred to neocortex. Multiple‑Trace/Trace‑Transformation Theory (MTT) – hippocampus is always required to retrieve detailed episodic memories, creating new traces with each retrieval; over time, semanticized (“gist”) versions can reside in neocortex, but vivid recall remains hippocampal‑dependent. Scene‑Construction (Reconstruction) Theory – neocortex stores the elements of an event permanently, but the hippocampus is needed at recall to reconstruct a coherent episodic scene from those distributed cortical traces.

Answer 143

Standard Consolidation Theory (SCT) – hippocampus is essential for recent episodic memories but not for remote memories once they’ve been fully transferred to neocortex.

Answer 144

Multiple‑Trace/Trace‑Transformation Theory (MTT) – hippocampus is always required to retrieve detailed episodic memories, creating new traces with each retrieval; over time, semanticized (“gist”) versions can reside in neocortex, but vivid recall remains hippocampal‑dependent.

Answer 145

Scene‑Construction (Reconstruction) Theory – neocortex stores the elements of an event permanently, but the hippocampus is needed at recall to reconstruct a coherent episodic scene from those distributed cortical traces.

Answer 146

1. Hippocampus is required for episodic memory acquisition (conversion of STM to LTM) 2. Hippocampus is NOT required for STM recall. 3. Hippocampus is NOT required for storage or recall of semantic information.

Answer 147

Over time, episodic memories can be transformed into semantic memories. After this “conversion,” recall of those memories may become independent of the hippocampus. This predicts that hippocampal lesions should spare “basic” recall of very old memories.

Answer 148

MTL amnesics often show intact “basic” remote recall, suggesting no overt deficit. However, detailed (“rich”) recall - including perceptual detail, viewpoint specificity, vividness, judgments of recollection, and relational associations- may still require the hippocampus. Thus, hippocampal damage may selectively impair the quality rather than the existence of old episodic memories.

Answer 149

If you test only for basic recognition (e.g. “Do you remember this event?”), amnesics perform well. To reveal their deficit, you must probe the richness of recall (e.g. “Describe what you saw,” “How vivid was it?”). Therefore, success or failure in remote‐memory tasks depends crucially on how (and how deeply) you test memory.