Chapter 6: Memory

What Is Memory?

• Definition: The ability to store and retrieve information over time.

• Three Key Functions:

  • Encoding: Transforming perceptions into enduring memories.

  • Storage: Maintaining memories over time.

  • Retrieval: Bringing memories to mind.

Encoding: Transforming Perceptions into Memories

• Process of memory formation: Combines existing information with new incoming information.

• Major Types of Encoding:

  • Semantic Encoding: Relating new information meaningfully to existing knowledge.

  • Visual Imagery Encoding: Storing information as mental images.

  • Organizational Encoding: Categorizing information based on relationships among items.

Storage: Maintaining Memories Over Time

• Sensory Storage: Holds brief sensory information (seconds or less).

  • Iconic Memory: Visual sensory storage.

  • Echoic Memory: Auditory sensory storage.

• Short-Term Storage & Working Memory:

  • Short-Term Memory (STM): Holds nonsensory info for more than a few seconds but less than a minute (approx. 7 items). Includes rehearsal and chunking strategies.

  • Working Memory: Actively maintains and manipulates information; involves the episodic buffer, visuo-spatial sketchpad, and phonological loop.

Long-Term Storage (LTM)

• Extended retention for hours, days, years; no known capacity limits.

• Ability to recall items after long durations (e.g., 50 years after graduation).

The Hippocampus and Memory

• Role in Memory Formation:

  • Case of HM: Removal of the hippocampus led to anterograde amnesia (inability to form new long-term memories).

  • Consolidation: Stability of memories over time.

  • Reconsolidation: Memories can be disrupted when recalled and need to stabilize again.

Enhancing Memory Consolidation

• Sleep: Crucial for memory consolidation and targeted memory reactivation (TMR) enhances memory storage, especially for weakly learned information.

Memory Neural Foundations

• Long-term potentiation (LTP): Strengthens synaptic connections; the NMDA receptor regulates information flow and LTP.

Retrieval: Reinstating the Past

• Retrieval Cues: Information may be retrievable through external cues that help bring stored information to mind.

• Encoding Specificity Principle: Retrieval cues should match encoding contexts for effective recall.

• State-Dependent Retrieval: Information is recalled better in the same state as when it was encoded.

Consequences of Retrieval

• Retrieval can strengthen memories or impair others (e.g., retrieval-induced forgetting).

• Memory accuracy can change based on the act of retrieval.

Forms of Long-Term Memory

• Explicit vs. Implicit Memory:

  • Explicit Memory: Direct recall of past experiences (semantic and episodic memory).

  • Implicit Memory: Influence of past experiences on behavior without conscious recollection (procedural memory and priming).

• Semantic and Episodic Memory:

  • Semantic Memory: General knowledge and facts about the world.

  • Episodic Memory: Personal experiences tied to specific times and places, enabling mental time travel and imagination.

Memory Failures: The Seven "Sins" of Memory

• Transience: The tendency to forget; memory fades quickly at first, then slower over time.

  • Involves interference (retroactive and proactive).

• Absentmindedness: Memory lapses due to divided attention; less frontal lobe activity during distractions.

  • Tip-of-the-Tongue Phenomenon: Knowledge available but not easily retrievable.

• Misattribution: Assigning a recollection to the wrong source; false recognition can occur.

• Suggestibility: Incorporating misleading information into memories due to external sources.

• Bias: Distortions influenced by present beliefs and emotions which alter recall of past experiences.

• Persistence: Intrusive recollections of undesired events or memories of emotional experiences (flashbulb memories).

Conclusion: Costs and Benefits of Memory Sins

• The seven “sins” highlight memory's fallibility, yet they also serve adaptive functions for everyday life.