Essentials of Memory Systems & Amnesia

Memory Systems

  • Short-term memory (working memory): Keeps information while you are actively working on it. Without rehearsal, information is lost quickly.
  • Long-term memory: More enduring storage of information.
  • Declarative memory (explicit memory)
  • Non-declarative memory (implicit memory)

Components of Memory

  • Declarative (Explicit) Memory:
    • Involves intentional recollection of previous experiences (conscious, accessed directly).
    • Factual information (words, definitions, names, concepts).
    • Episodic Memory: Events, chronological, or temporally dated recollections of personal experiences.
    • Semantic Memory: Facts, general knowledge not tied to when the information was encoded.
  • Non-Declarative (Implicit) Memory:
    • Apparent when retention is exhibited on a task that does not require intentional remembering (unconscious, accessed indirectly).
    • Procedural: Skills and habits.
    • Priming
    • Simple classical conditioning
    • Non-associative learning

Amnesia

  • Pathological loss of memory.
  • Retrograde Amnesia: Loss of memories for events that occurred prior to the onset of amnesia.
  • Anterograde Amnesia: Loss of memories for events that occur after the onset of amnesia.

Medial Temporal Lobe (MTL)

  • Important for forming new long-term memories.
  • Newly formed memories are dependent on the MTL.
  • MTL is not a permanent storage site for long-term memories.

Non-Medial Temporal Lobe Amnesia

  • Korsakoff's Syndrome
  • NA case study
  • Alzheimer's Disease
  • Post-trauma

Korsakoff’s Syndrome

  • Consequence of alcohol abuse, leading to sensory and motor problems, disorientation, confusion, confabulation, personality changes.
  • Thiamine deficiency.
  • Severe retrograde AND anterograde amnesia (mainly episodic).

Alzheimer’s Disease

  • Pathology: neurofibrillary tangles & amyloid plaques, reductions in neurotransmitters.
  • Progressive and terminal leading to dementia.
  • Progressive amnesia (anterograde and retrograde).
  • Explicit and some implicit memory deficits.

Post-Traumatic Amnesia

  • Confusion on regaining consciousness.
  • Cannot remember time right before incident (retrograde) and events since onset of confusion (anterograde).
  • Confusion period lasts longer than time spent in coma.

Non-Declarative Memory in the Brain

  • Cerebellum: sensorimotor skills.
  • Striatum: stimulus-response associations.

Striatum

  • Important for learning and retrieving specific responses to specific stimuli.

Hippocampus

  • Involved in spatial memory.
  • Functions in memories for spatial location, based on external location cues.

Long-Term Memory Theory

  • Enduring changes in the efficiency of synaptic transmission are the basis of long-term memory.
  • Pre-synaptic neuron must successfully produce a change in the post-synaptic neuron (Hebbian synapse).

Long-Term Potentiation (LTP)

  • Long-lasting facilitation of synaptic transmission.
  • "Neurons that fire together, wire together".

NMDA Receptor

  • Glutamate must bind to NMDA receptor.
  • Allows calcium ions (Ca+2) through its central channel into post-synaptic neuron.
  • Calcium activates protein kinases and sparks LTP.