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.