Amnesia2023_updated

Amnesia Overview

  • Amnesia types: organic and psychogenic.

Types and Causes of Amnesia

  • Anterograde Amnesia (AA)

    • Impairment: encoding, storing, retrieving new memories.

    • Preserved: language, intelligence, working memory, implicit memory.

  • Retrograde Amnesia (RA)

    • Inability to recall past memories.

    • Temporal gradient: earlier memories are better preserved.

Organic Amnesia

  • Caused by physical brain damage.

  • Generally irreversible and severe.

Causes of Organic Amnesia

  • Alzheimer's disease (AD)

    • Degenerative disorder affecting memory and cognition.

  • Korsakoff’s syndrome

    • Thiamine deficiency, often linked to alcoholism.

  • Herpes Simplex Encephalitis (HSE)

    • Viral infection with known onset.

  • Temporal lobe surgery

    • Specific lesions leading to amnesia (e.g., patient HM).

  • Other causes: strokes, tumors, traumatic brain injuries.

Brain Structures Involved

  • Hippocampus

    • Critical for forming new memories.

  • Diencephalon

    • Involved in memory processing and retrieval.

Characteristics of Organic Amnesia

  • Anterograde Amnesia

    • Difficulty in forming new memories after the onset.

  • Retrograde Amnesia

    • Varies in severity regarding past memories.

Preserved Functionality in Anterograde Amnesia

  • Procedural Memory

    • Skills learned without conscious awareness (e.g., HM learning mirror drawing).

  • Classical Conditioning

    • Learned responses (e.g., pin concealed, tone-based conditioning).

  • Priming

    • Indirect or implicit learning tasks showing preserved functionality.

Examples of Learning in Amnesia

  • Procedural Learning

    • Corkin's studies on HM’s motor skills.

  • Classical Conditioning

    • Studies showing response conditioning without recall.

  • Priming

    • Demonstrating ability to identify degraded images or words through indirect tasks.

Familiarity and Recollection in Amnesia

  • Recognition involves:

    • Familiarity: automatic and unconscious.

    • Recollection: controlled and conscious.

  • Amnesics may show intact familiarity but struggle with recollection of details.

Retrograde Amnesia

  • Characterized by difficulty retrieving pre-onset memories.

  • Testing methods include:

    • Recognition tests of famous historical figures and memory recollection.

  • Temporal Gradient

    • Earlier memories (from years back) are more preserved compared to more recent memories.

Theories on Amnesia

  • Systems Consolidation Theory

    • Memory consolidation from hippocampus to neocortex.

  • Multiple Trace Theory (MTT)

    • Essential involvement of hippocampus in memory retrieval.

  • Memory Transformation Account

    • Memory evolves from detail-dependent to gist-based over time.

Reading Suggestions

  • Organic Amnesia: Baddeley, chapters on amnesia.

  • Psychogenic Amnesia: Baddeley, selected pages.