How do we store memories?

memory storage

This article is going to explore areas of cognitive psychology; how do we store memories? By exploring the different areas of the brain involved in memory storage, episodic memory and discussing different theories of memory and forgetting.

WHAT IS EPISODIC MEMORY?

Episodic memory is a personally experienced event(s) in time and space. That is not stored in just one brain region! Specific aspects of memory are initially processed in dedicated cortical areas, shown below:

memory

EPISODIC MEMORY: BINDING

As in perception, aspects must be “bound”. Working Memory is an episodic buffer where information that is attended (i.e. Central Executive, located in Frontal Lobes) and processed in difference brain regions. Working memory is bound together into an integrated memory representation (episode) by the Hippocampus.

memory

memory

HIPPOCAMPUS (HC)
  • Means seahorse in Latin!
  • Essential for declarative memory
  • Located in medial-temporal lobe
  • Without the hippocampus only the learning of skills and habits, simple conditioning, and priming can occur (i.e. Non-declarative memory)
  • Hippocampus establishes bound representations using similar neural processes as learning
    • Creating new synapses
    • Presynaptic facilitation
    • Long-term potentiation
HIPPOCAMPUS: MEMORY CONSOLIDATION

New memories go through a process of strengthening which is called consolidation. “New memories are clear but fragile, and old ones are faded but robust” (Wixted, 2004)

Eichenbaum (2001): Two stage Consolidation

  1. Hours: strengthening of neural connections within the hippocampus
  2. Days/Years: strengthening of neural connections between the hippocampus and cortical regions responsible for perceptual processing
LAWS OF DECAY AND DISRUPTION

Ribot’s Law (1882)

  • Newly formed memories will be effected more by brain injury than older memories
  • Newer memories are at an earlier stage of consolidation and, therefore more vulnerable

Jost’s Law (1897)

  • The older of two memories of the same strength will decay slower
  • Older memories have received more consolidation
MOTIVATED FORGETTING

Sometimes unpleasant memories may be forgotten as a defence mechanism, to protect oneself from material that is too painful, anxiety or guilt producing, or otherwise unpleasant.  Theories about motivated forgetting tend to incorporate ideas from psychoanalysis, counselling, etc:

  • Repression: all memory of event/experience blocked from conscious awareness
  • Dissociation: the creation of a “psychological distance” between themselves and the memory.

Does motivated forgetting require a special memory mechanisms?

  • Some memories (especially emotional) can be held in memory for a very long time
  • Memories can be “lost” and then recovered
    • Inability to recall memory does not mean the memory doesn’t exist
    • The method of retrieval is inappropriate e.g. wrong cue
    • With right method “lost” memory can be recovered
  • Traumatic memories (such as child abuse) may be “lost” due to basic memory mechanisms and not require specific processes.
PROBLEMS WITH MEMORY RECOVERY
  • Are recovered memories true?
    • More errors in recalling older memories
    • We can have false recollection of whole episodes
    • False memories are more likely when they are plausible
    • False memories are recalled as vividly as real memories
    • Attempts to recover “lost” memories may provide misinformation which contributes to false memory.
    • Personal belief in memory is no sign of veracity
    • Can only confirm memory with “hard” evidence

Motivated Forgetting continues to be an area of complex debate and a nightmare for the legal system

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