L2: LTM

Long-term Memory Overview

  • Amnesia: Understanding the mechanisms of memory impairment and the distinction between different types of memory.
  • Varieties of Long-Term Memory: Includes explicit memory (declarative) and implicit memory (non-declarative).

Multi-Store Model (Atkinson & Shiffrin)

  • Environmental Input: Stimulus from the environment that initiates sensory processing.
  • Sensory Memory:
    • Duration: < 1 second
    • Capacity: Large
  • Short-Term Memory (STM):
    • Duration: 30 seconds
    • Capacity: Limited
  • Long-Term Memory (LTM):
    • Duration: Unlimited
    • Capacity: Large
  • Memory Processes:
    • Maintenance Rehearsal: Process for holding information (STM).
    • Elaborate Rehearsal: Leads to long-term storage.
    • Forgetting:
    • Decay: Loss of memory over time.
    • Interference: Competing information disrupts retrieval.

Evidence for Distinction Between Memory Types

Duration and Capacity Differences
  • Different durations and capacities provide evidence for distinct memory systems.
Serial Position Curve
  • Primacy Effect: Recall of first items due to longer rehearsal.
  • Recency Effect: Recall of last items; items still in STM.
  • Notable Changes:
    • Primacy effect remains stable across delays.
    • Recency effect diminishes with delay due to STM decay.
Brain Damage Evidence
  • Selective STM Deficits: Specific brain damage leading to impaired STM, while LTM remains intact (Case Study of Patient KF).
  • Studies show patients can preserve LTM functions while exhibiting deficits in STM.

Amnesia

  • Types of Amnesia:
    • Retrograde: Loss of memories prior to trauma.
    • Anterograde: Inability to form new memories post-trauma.
  • Functional Preservation:
    • Amnesiacs retain language skills and can hold conversations.
    • STM and IQ remain unaffected.
Key Case Studies
  • Patient KF:
    • Left parietal-occipital lobe damage.
    • Preserved LTM despite impaired STM.
  • Patient H.M.:
    • Medial temporal lobe damage.
    • Experiments showed differences in recall and recognition tasks.

Types of Long-Term Memory

Taxonomy
  • Declarative Memory (explicit):
    • Episodic Memory: Personal experiences and events.
    • Semantic Memory: Facts and knowledge.
  • Non-Declarative Memory (implicit):
    • Procedural Memory: Skills and tasks.
    • Classical Conditioning: Conditioned responses.
    • Priming and Nonassociative Learning: Learning through exposure.

Memory Tests and Tasks

Explicit vs. Implicit Memory
  • Explicit Tests: Can include free recall, cued recall, and recognition.
  • Implicit Tests: No intention to recall; includes tasks like fragment identification and word-stem completion.
  • Amnesiacs perform comparably to controls in implicit tests despite deficits in explicit tasks.

Consolidation in Long-Term Memory

  • Process: Strengthening of memory traces over time, switching from reliance on the hippocampus to neocortical areas.
  • Role of Sleep: Essential for protecting and promoting memory consolidation.
    • Muller & Pilzecker (1900): Demonstrated delay enhances recall.
    • Gais et al. (2006): Showed sleep protects learning from interference.
  • Understanding Consolidation: It's an ongoing process crucial to fortifying memory retrieval and storage.

Summary of Key Points

  • Amnesics show impairments in declarative memory tasks but retain abilities in non-declarative tasks.
  • The study of memory types and the effects of amnesia provide insights into the complexity of human memory systems.