Learning and memory Flashcards
Who is HM and what we have found by studying him?
HM (Henry Molaison) was a patient who underwent bilateral medial temporal lobe resection (removal of amygdala, hippocampus, part of frontal cortex) to treat epilepsy. As a result, he developed severe anterograde amnesia, meaning he could not form new explicit memories, though his IQ and personality remained intact.
Key Findings from Studying HM:
1. Hippocampus is essential for forming new explicit (declarative) memories, but not for retrieving old ones.
2. Short-term and working memory were preserved, but long-term explicit memory formation was impaired.
3. Implicit memory (procedural learning) was intact – shown through tasks like mirror tracing, where he improved over time despite having no recollection of practicing.
4. Memory is not a single process – different brain structures support different types of memory (e.g., hippocampus for declarative memory, basal ganglia for procedural memory).
HM’s case revolutionized our understanding of memory systems and brain function.
What kind of memory tests HM fail to do well?
HM failed in tests that required explicit (declarative) memory, particularly those involving new learning and recall. Some key tests he struggled with include:
1. Recognition and Recall Tests
* Given a list of words or images to study, he performed poorly when asked to recall them later. (Can’t even remember receiving the list)
* Paired-association tasks: He could not learn and remember word pairs.
2. Digit Span +1 Task
* He could repeat a short sequence of numbers but difficult to solve problem once the sequence exceeded e.g., 7±2, showing limited short-term to long-term memory transfer.
What’s priming tasks and perceptual identification task, and what have found by studying wit HM
Priming Tasks & Perceptual Identification Task
1. Priming Tasks
* Involves exposure to a stimulus that influences a later response without conscious awareness.
* Example: Word Stem Completion – HM was given a list of words to study, then later shown word fragments (e.g., “app___”) and asked to complete them.
* Finding: HM was more likely to complete the words with those he had seen earlier, despite having no recollection of seeing them before.
2. Perceptual Identification Task
* Involves showing words/images very briefly (hard to consciously perceive) and asking participants to identify them.
* Finding: HM was better at identifying words/images he had seen earlier, even though he had no memory of studying them.
Key Conclusion from HM’s Performance
* Priming and perceptual learning rely on implicit memory, which does not require the hippocampus.
* HM’s intact priming ability suggests that implicit memory is supported by different brain structures (e.g., neocortex) rather than the medial temporal lobe.
What’s mirror tracing task and what’s been found in HM’s study?
Mirror Tracing Task
* A procedural learning task where participants trace a shape while only viewing their hand through a mirror, making coordination more difficult.
* It measures motor learning and implicit memory.
Findings in HM’s Study
* HM improved across trials, making fewer errors each day.
* Despite his improvement, he had no memory of ever doing the task before.
* This demonstrated that procedural memory (motor learning) was intact, even though declarative memory (explicit recall of learning) was impaired.
Key Conclusion
* The hippocampus is not necessary for procedural memory. Instead, the basal ganglia and cerebellum play a major role in motor learning.
* Memory is not a single system—declarative and procedural memory rely on different brain structures.
What is declarative and non declarative memory?
- Declarative (Explicit) – Conscious recall of facts/events (Hippocampus).
- Episodic – Personal experiences (“I had coffee this morning”).
- Semantic – General knowledge (“Paris is the capital of France”).
- Non-Declarative (Implicit) – Unconscious learning, influences behavior (Basal Ganglia, Cerebellum).
- Procedural – Skills/habits (riding a bike, mirror tracing).
- Priming – Prior exposure affects response (word stem completion).
- Classical Conditioning – Associative learning (fear conditioning).
- Non-Associative – Habituation & sensitization.
Key Difference – Declarative requires conscious recall, Non-Declarative is automatic.
HM’s Case – Lost declarative memory but retained non-declarative memory (e.g., improved at mirror tracing but had no memory of learning it).
What’s the familiarity we can found in HM’s test of learning.
- Test – HM was shown images he had seen before and asked to choose between a familiar and unfamiliar one (two-alternative forced choice task).
- Finding – He performed well, often selecting the previously seen image, despite having no recollection of seeing them before.
Key Conclusion – Familiarity-based recognition can occur without explicit recall, suggesting some forms of recognition memory do not depend on the hippocampus.
What’s the tests of association (classical conditioning paradigms) HM took and what’s found
- Test – HM was exposed to neutral stimuli (e.g., a tone) paired with an unconditioned stimulus (e.g., a puff of air to the eye) that naturally elicited a blink reflex.
- Finding – He successfully acquired conditioned responses, blinking in response to the tone alone after repeated pairings.
Key Conclusion – Classical conditioning does not require the hippocampus; instead, cerebellar circuits support this form of learning.
HM could be classical conditioned even tho he do not realize he had been exposed to the tone.
What’s the other two similar but difference cases to HM, N.A and Clive wearing. What’s the impairment and what’s the influence.
Case of Patient N.A.
* Cause – A fencing accident that resulted in damage to the dorsomedial thalamus(背内侧丘脑) and mammillary bodies(乳头体), which are part of the medial diencephalon(间脑内侧区).
* Impairment – Severe anterograde amnesia, especially for declarative memory, but with intact procedural memory.
* Preserved Abilities – Could still learn new motor skills and had normal intelligence and working memory, similar to HM, but with less severe retrograde amnesia.
Key Influence on Memory Research
* Showed that memory formation is not solely dependent on the hippocampus, as damage to the medial diencephalon also leads to anterograde amnesia.
* Reinforced the idea that the hippocampus and diencephalon form a connected network essential for encoding new declarative memories.
* Demonstrated that non-declarative memory (e.g., motor learning) does not rely on the hippocampus or diencephalon, similar to findings from HM.
* Clive Wearing * Impairment – Profound anterograde and retrograde amnesia due to herpes simplex encephalitis (脑炎), unable to form new memories and lost most past memories. * Influence – Demonstrated severe disruption of declarative memory, but procedural memory (e.g., playing the piano) remained intact, reinforcing the distinction between explicit and implicit memory systems.
What‘s the case of Patient K.C.
Case of Patient K.C.
* Cause – A motorcycle accident that caused extensive brain damage, including the hippocampus(海马体), parahippocampal cortex(旁海马皮层), and frontal cortex(额叶皮层).
* Impairment – Severe episodic memory loss, unable to recall personal past experiences (retrograde amnesia), and anterograde amnesia, unable to form new explicit memories.
* Preserved Abilities – Semantic memory remained intact (e.g., he could recall factual knowledge but not personal events), could converse normally, and still retained procedural skills like playing chess, despite not remembering how he learned them.
Key Influence on Memory Research
* Provided strong evidence that episodic and semantic memory are dissociable, meaning personal experiences and factual knowledge rely on different brain mechanisms.
* Confirmed that the hippocampus is critical for forming and retrieving episodic memories but is not necessary for semantic or procedural memory.
Key Conclusion – Patient K.C.’s case demonstrated that episodic memory requires the hippocampus, while semantic and procedural memory can be preserved despite severe hippocampal and cortical damage.
What can we learn about long-term memory from case study of HM, K.C, etc.
- Memory is not a single system – Different types of long-term memory rely on distinct brain structures.
- Hippocampus is essential for declarative memory – HM and K.C. showed that hippocampal damage leads to anterograde amnesia, preventing the formation of new explicit memories.
- Episodic and semantic memory are dissociable – K.C. lost episodic memory but retained semantic knowledge, proving that personal experiences and general facts are stored differently.
- Procedural memory is independent of the hippocampus – HM and K.C. could still learn motor skills (e.g., mirror tracing, chess), showing that the basal ganglia and cerebellum support procedural memory.
Key Conclusion – Long-term memory consists of multiple subsystems (episodic, semantic, procedural), supported by different neural structures rather than a single memory center.
Why are some memory conscious and some not
- Declarative Memory (Conscious) – Requires active recall and awareness, supported by the hippocampus and medial temporal lobe.
- Episodic Memory – Remembering personal experiences (e.g., “I went to a concert last year”).
- Semantic Memory – Storing facts and general knowledge (e.g., “Paris is the capital of France”).
- Non-Declarative Memory (Unconscious) – Does not require awareness and influences behavior automatically, relying on structures like the basal ganglia, cerebellum, and neocortex.
- Procedural Memory – Skills and habits (e.g., riding a bike, playing chess).
- Priming – Exposure to stimuli influences responses without conscious effort.
- Classical Conditioning – Associative learning (e.g., blinking to a tone after pairing with an air puff).
Key Conclusion – Conscious memory (declarative) depends on the hippocampus, while unconscious memory (non-declarative) relies on subcortical structures, allowing us to perform complex behaviors without deliberate thought.
What’s the Proposed information flow.
- Information Flow – Sensory information flows from association cortices(联想皮层) into the parahippocampal cortex(旁海马皮层) and perirhinal cortex(梨状皮层), then converges in the entorhinal cortex(内嗅皮层), the main gateway to the hippocampus(海马体).
- Convergence in the Hippocampus – The entorhinal cortex(内嗅皮层) sends information to the dentate gyrus(齿状回), which then projects to CA3 region(CA3区) and subsequently to CA1 region(CA1区), where different inputs are integrated into a coherent memory representation.
- “Highway of Memory” – The fornix(穹窿) serves as the primary output pathway of the hippocampus, transmitting processed memory information to the mammillary bodies(乳头体) and anterior thalamus(丘脑前部), which further contribute to memory consolidation and distribution.
Key Conclusion – The hippocampus(海马体) functions as a memory integration hub, organizing and encoding information before relaying it through the fornix(穹窿) to other brain regions for long-term storage and retrieval.
What’s the different contributions to declarative memory?
Most declarative memory for facts and events consists of two components: the sense of familiarity with the features of the item (“I’ve seen that actress somewhere…”), and additionally recollection of the item in the specific context in which it was presented (“Oh, she played Daenerys in Game of Thrones”).
Perirhinal cortex is thought to be responsible for the sense of familiarity in memory, whereas recollection of the item is the function of the hippocampus. Processing of contextual aspects of memory (including spatial cognition, which we will discuss in more detail a little later) appears to depend especially on the parahippocampal cortex
In general, the performance of experimental animals suggests that the hippocampus acts as the final stage of convergence for adjacent regions of cortex.
In keeping with this schema, people with specific hippocampal damage appear to have difficulties with recollection, while familiarity-based aspects of memory are spared. Conversely, people with surgical lesions that include the perirhinal cortex but not the hippocampus experience impaired familiarity with stimuli despite preserved recollection. The medial temporal lobe is not the only brain region required to form new declarative memories (amygdala can enhance familiarity in memory test).
What’s the definition of learning and memory
Learning is the process of acquiring new information.
Memory is the ability to store and retrieve information. The specific information stored in the brain.
where is hippocampus?
Hippocampus
* Interior medial aspect of the
temporal lobe
* Extends into a structure called
the fornix (connects to the
mammillary body
* Latin for seahorse
Path way: receive LEC and MEC inputs, -> dentate gyrus -> CA 3 -> CA 1.
What is the associational/convergence hierarchy to hippocampus?
Ventral Stream(腹侧通路) → LEC(侧内嗅皮层) – Processes “what” information, handling object recognition, features, and non-spatial context.
Dorsal Stream(背侧通路) → MEC(内侧内嗅皮层) – Processes “where” information, supporting spatial navigation, movement tracking, and environmental mapping.
Hippocampus(海马体) as the Integration Center
Combines object (LEC) and spatial (MEC) information into a unified episodic memory.
Key Takeaways - The ventral stream identifies objects, while the dorsal stream encodes spatial locations before reaching the hippocampus.
This dual-stream system enables episodic memory formation, linking what happened and where it happened.
Key Difference – LEC focuses on what is in the environment (objects and context), while MEC focuses on where things are (spatial positioning and movement). Both feed into the hippocampus, where information is integrated for episodic memory formation.
What’s the goal of open field observation?
Open Field Observation: Purpose and Process
Open field observation is a behavioral experiment designed to study how neurons in the hippocampus and entorhinal cortex respond to spatial exploration. The goal is to identify and define receptive fields for neurons involved in navigation and memory processing.
How It Works:
* An animal (typically a rat or mouse) is placed in an open, unmarked arena and allowed to freely explore.
* Neural activity is recorded to analyze how different brain regions encode spatial and contextual information.
* Researchers aim to identify place cells(位置细胞)in the hippocampus, which fire when the animal is in a specific location.
* They also look for grid cells(网格细胞)in the medial entorhinal cortex(MEC, 内侧内嗅皮层), which fire in a regular grid-like pattern, forming a spatial coordinate system.
* Understand how spatial and non-spatial information is processed in the hippocampal network.
Key Takeaway
Open field observation helps researchers understand how the brain encodes space and movement, revealing the neural basis of navigation, memory, and spatial representation.
What’s place cells and grid cells and what could they tell us?
Place Cells & Grid Cells: What They Are and What They Tell Us
Place Cells(位置细胞)
* Found in the hippocampus(海马体), these neurons fire when an animal is in a specific location within an environment.
* Each place cell is associated with a particular “place field”, meaning it becomes active only when the animal is in that specific area.
Grid Cells(网格细胞)
* Found in the medial entorhinal cortex(MEC, 内侧内嗅皮层), these neurons fire in a hexagonal (六角) grid pattern across an environment.
* Unlike place cells, grid cells do not correspond to a single location but create a repeating, structured spatial map. Grid system keep tract space of where we have been and where we’re going. It knows the pattern from a -> b -> C, where’s place cell do not know that pattern.
What They Tell Us About the Brain
* Place cells represent specific locations, helping form a mental map of the environment.
* Grid cells provide a coordinate system, allowing for path integration and navigation.
* Together, they reveal that the hippocampus and entorhinal cortex work together to encode spatial memory, supporting navigation and episodic memory formation.
Key Takeaway – Place cells and grid cells are fundamental to understanding how the brain processes space, forms memories, and enables navigation.
What’s border cells?
Border Cells(边界细胞)
* Location – Found in the medial entorhinal cortex (MEC, 内侧内嗅皮层) and some hippocampal regions.
* Function – Fire when an animal is near a boundary, such as a wall or edge of an environment.
* Consistency – Their activity remains stable regardless of the size or shape of the environment, meaning if a new wall is added, a new border field forms in alignment with it.
Key Takeaway – Border cells help animals recognize and navigate within enclosed spaces, ensuring that memory representations include environmental boundaries.
What’s head direction cells
Head Direction Cells(头方向细胞)
* Location – Found in the medial entorhinal cortex (MEC, 内侧内嗅皮层), anterior thalamus (丘脑前部), and other navigation-related brain areas.
* Function – Fire when an animal’s head is facing a specific direction, regardless of location.
* Characteristics – Each cell has a preferred firing direction, similar to a compass, and remains active as long as the head maintains that orientation.
Key Takeaway – Head direction cells provide an internal sense of direction, helping animals maintain spatial orientation even in the absence of external cues.
What does open field studies reveal?
Open Field Studies – MEC contains grid cells (spatial coordinate system), border cells (detect boundaries), and head direction cells (track orientation).
Conclusion – MEC is crucial for space and movement-related firing.
Alzheimer’s Disease Impact – MEC is one of the first affected regions, leading to spatial memory deficits, getting lost in familiar places, and difficulty with complex navigation tasks.
Future Research – How adding objects to the open field affects spatial representation.
What’s object cells and trace cells?
Object Cells & Trace Cells
* Object Cells(物体细胞) – Found in the lateral entorhinal cortex (LEC, 侧内嗅皮层), these neurons fire when an object is present in a specific location. Some object cells respond to specific objects, while others track new vs. familiar objects. They help link objects to experiences, supporting episodic memory.
* Trace Cells(痕迹细胞) – A subtype of object cells in the LEC that continue to fire even after an object is removed. They help track where an object was, allowing the brain to maintain a temporal representation of objects, which is essential for memory formation and recall.
Key Difference – Object cells respond to the presence of objects, while trace cells keep firing even after the object is no longer there, maintaining a memory trace of its past location.
What’s lesion studies?
Two tasks tested how LEC (lateral entorhinal cortex) and MEC (medial entorhinal cortex) lesions affect object recognition vs. context recognition.
Task 1: Object Recognition
• Setup – Mice saw three objects over three trials. In the fourth trial, one object was replaced with a duck.
• Results
• Control Group – Increased exploration, indicating they noticed the object change.
• LEC Lesion – No increase, showing LEC is critical for object recognition.
• MEC Lesion – Slight increase, suggesting MEC plays a minor role.
• Takeaway – LEC is required for object recognition, while MEC has limited involvement.
Task 2: Context Recognition
• Setup – Instead of changing an object, the background was altered in the fourth trial.
• Results
• Control Group – Increased exploration, meaning they noticed the background change.
• LEC Lesion – Slight increase, suggesting LEC has some role in context processing.
• MEC Lesion – No increase, showing MEC is essential for recognizing background changes.
• Takeaway – MEC is required for context recognition, while LEC has minor involvement.
Overall Findings
• LEC (Lateral Entorhinal Cortex) → Object recognition (what changed).
• MEC (Medial Entorhinal Cortex) → Context recognition (background changed).
• Control mice detected both changes, confirming LEC’s role in object memory and MEC’s role in spatial/context memory.
what does the place field told us?
Place fields - the area in space that elicit firing in a place cell of the hippocampus
The hippocampus functions as a spatial map, and the hippocampus fires not only in a specific spot, but when something specific is happening in that spot. (老鼠看正前方时,侧方的direction cell 也在firing只是没有正前方的active,然后direction cell的input也没有place cell在hippocampus里fire的强)。