2022-04-25 10:14:20

Announcements

  • Exam 4, Tuesday, May 3, 12:00 PM (noon) - 10:00 PM

Today’s topics

Review from last time

Memory systems in the brain

Review from last time

  • Learning and memory involve changes in neural firing, circuitry
  • Hebbian learning a type of associative learning
  • NMDA receptor as coincidence detector
    • Molecular basis of one form of long-term potentiation (LTP)
  • Different types of information stored in different brain systems
  • Wrap-up on learning and memory

Disorders of memory

Patient HM (Henry G. Molaison)

  • Intractable/untreatable epilepsy
  • Bilateral resection of medial temporal lobe (1953)
  • Epilepsy now treatable
  • But, memory impaired
  • Lived until 2008

HM’s surgery

Brenda Milner tells the story

Amnesia

  • Acquired loss of memory
  • ≠ normal forgetting
  • Note: computers don’t forget

HM’s amnesia

  • Retrograde amnesia
    • Can’t remember 10 yrs before operation
    • Distant past better than more recent
  • Severe, global anterograde amnesia
    • Impaired learning of new facts, events, people
  • But, skills (mirror learning) intact

Types of amnesia

  • Retrograde (‘backwards’ in time)
    • Damage to information acquired pre-injury
    • Temporally graded
  • Anterograde (‘forward’ in time)
    • Damage to information acquired/experienced post-injury

What it’s like

Every day is alone in itself, whatever enjoyment I’ve had, and whatever sorrow I’ve had…Right now, I’m wondering, have I done or said anything amiss? You see at this moment, everything looks clear to me, but what happened just before? That’s what worries me. It’s like waking from a dream. I just don’t remember.

What it’s like

Other causes of amnesia

  • Disease
    • Alzheimer’s, herpes virus
  • Korsakoff’s syndrome
    • Result of severe alcoholism
    • Impairs medial thalamus & mammillary bodies

Patient NA

  • Fencing accident
  • Damage to medial thalamus
  • Anterograde + graded retrograde amnesia
  • Are thalamus & medial temporal region connected?

Patient NA

Spared skills in amnesia

  • Skill-learning
  • Mirror-reading, writing
  • Short-term memory
  • “Cognitive” skills
  • Priming

What does amnesia tell us?

  • Long-term memory for facts, events, people
  • ≠ Short-term memory
  • ≠ Long-term memory for “skills”
  • Separate memory systems in the brain?

Alzheimer’s Disease (AD)

  • Chronic, neurodegenerative disease affecting ~5 M Americans
  • Cognitive dysfunction (memory loss, language difficulties, planning, coordination)
  • Psychiatric symptoms and behavioral disturbances
  • Difficulties with daily living
  • (Burns & Iliffe, 2009)

Progression

  • Post-mortem exams show \(\beta\) amyloid plaques and neurofibrillary tangles in hippocampus + other brain areas

AD Treatments

  • Acetylcholinesterase (AChE) inhibitors (e.g. Aricept)
    • ACh a neuromodulator in the brain
  • NMDA-R partial antagonists (e.g., Memantine)
  • Drugs that address amyloid \(\beta\) don’t work especially well
  • AD the result of disordered immune response?

Hippocampus

Hippocampus & medial temporal lobe areas

  • Dense in NMDA receptors
  • Formation, storage, consolidation of long-term episodic or declarative memories
  • Stores info for later transfer to cortex

Hippocampus in non-human animals

Cortical areas activated or deactivated during memory encoding

Cortical areas deactivated in non-memory cognitive tasks but activated during memory retrieval

Memory systems in the brain

References

Burns, A., & Iliffe, S. (2009). Alzheimer’s disease. BMJ, 338, b158. https://doi.org/10.1136/bmj.b158

Dickerson, B. C., & Eichenbaum, H. (2010). The episodic memory system: Neurocircuitry and disorders. Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology, 35(1), 86–104. https://doi.org/10.1038/npp.2009.126

Squire, L. R. (2004). Memory systems of the brain: A brief history and current perspective. Neurobiology of Learning and Memory, 82(3), 171–177. https://doi.org/10.1016/j.nlm.2004.06.005