Learning and Memory

Introduction

Memory is essential for tracking life events, personal identity, and learned experiences.
Memory functions through brain plasticity, allowing neural networks to retain and modify information.
Ribot’s Law: Older memories are more stable than newer ones.

Ribot’s Law: Why Are Older Memories More Stable?

Unlike institutions that remember recent changes best, the brain prioritizes older memories.
Evidence from multilingual individuals: Older languages are remembered longer than newer ones.
Case study: Einstein’s last words were lost due to a language barrier, emphasizing how memory retrieval changes over time.

The Mechanism of Memory

Movie Memento depicts anterograde amnesia, where new memories cannot form.
Aristotle’s analogy: Memory as wax imprints (early, inaccurate model of memory formation).
Memory formation involves physical changes in the brain, similar to a windshield crack from a rock.

Studies on Simple Learning and Memory

Sea slugs (Aplysia) demonstrate basic learning via neural adaptation.
Nobel Prize-winning work by Eric Kandel showed how synaptic strength changes with repeated stimuli.
Mammals exhibit more advanced memory, balancing retention and forgetting to prioritize relevant information.

Karl Lashley’s Research on Memory Storage

Lashley trained rats in a maze and made brain incisions, but they retained memory, proving distributed storage.
Memory is not localized in one area but distributed like cloud computing.

Memory Storage in the Brain

Neural networks encode memories by strengthening connections between neurons.
Donald Hebb’s theory: “Neurons that fire together, wire together.”
Long-term potentiation (LTP) and depression (LTD) strengthen or weaken synapses to encode information.
Artificial neural networks attempt to replicate biological memory, with mixed success.

The Stability-Plasticity Dilemma

Brains must balance learning new information while preserving older knowledge.
Artificial neural networks struggle with overwriting prior data.
The brain solves this by:
Selectively applying plasticity (via neuromodulators like acetylcholine).
Moving memories to different storage areas (e.g., hippocampus temporarily stores memories before transferring them).

Case Study: Henry Molaison (H.M.)

Removal of both hippocampi caused an inability to form new memories.
His old memories remained intact, proving memory relocates over time.

The Role of Pace Layering in Memory

Different types of learning operate at different speeds:
Fast-learning: Immediate memory, sensory experiences.
Mid-level: Habit formation, skill learning.
Slow-learning: Deeply ingrained knowledge and cultural values.
Brain plasticity operates across these layers to optimize memory storage.

Unique Memory Conditions

1. Hyperthymesia

Individuals remember autobiographical details perfectly.
Possibly caused by accelerated interactions between memory layers.

2. Synesthesia

Cross-wiring of sensory inputs (e.g., letters evoking colors).
Evidence suggests early childhood associations (e.g., Fisher-Price toy letters) imprint on synesthetic individuals.

3. Dissociative Amnesia (e.g., Jody Roberts & Ansel Bourne)

Loss of autobiographical memory but retention of skills and general knowledge.
Suggests memory is compartmentalized across different neural systems.

Different Types of Memory

Short-term memory: Temporary recall (e.g., remembering a phone number).
Long-term memory: Includes explicit (facts and events) and implicit (skills and habits) memory.
Memory Generalization vs. Specificity:
Some memory functions extract broad patterns (e.g., “apples are fruits”).
Others store precise details (e.g., “one red apple in a basket”).

Key Principles of Learning and Memory

Brains are not like computers: Memory retrieval is dynamic, context-dependent, and reconstructive.
Early experiences shape future learning: Neural connections are pruned based on environmental exposure.
Memory is context-dependent: Relevance determines retention.
Plasticity lasts a lifetime but diminishes over time: Sensitive periods exist for language, motor skills, and sensory adaptation.
Memory storage is distributed: Different memory types are processed in various brain regions.
Memory is multi-layered: Fast-learning systems feed into long-term stable memory layers.

Practical Applications

Enhancing Memory Retention:
Focus on relevance to reinforce learning.
Engage multiple senses and emotional contexts to solidify memories.
Use novelty and variation to maintain cognitive flexibility.
Avoiding Memory Distortions:
Recognize that memory is fallible (e.g., false eyewitness testimonies).
Be aware of post-event misinformation that can reshape past recollections.
Cognitive Maintenance in Aging:
Engage in socially and intellectually stimulating activities.
Avoid repetitive, monotonous routines.
Maintain physical health to support brain function.

Conclusion

Memory is a dynamic and evolving process shaped by neural plasticity.
Learning and retention depend on selective encoding, relevance, and storage mechanisms.
Future advancements in neuroscience and artificial intelligence will continue to uncover the intricacies of how memories are formed, stored, and retrieved.

This structured overview highlights the essential principles from the lecture on learning and memory while ensuring readability and clarity. Let me know if you’d like any refinements!