Amnesia PPT

what is amnesia?

• refers to memory loss

• most often associated w/ damage to the hippocampus and/or medial temporal lobe

  • specific → explicit LTM: episodic & NEW semantic memory

types of amnesia

• anterograde amnesia

• retrograde amnesia

  • temporally graded

anterograde amnesia

• inability to form new explicit memories

• difficulty form new explicit LTM

• new/”going forward”

retrograde amnesia

• inability to remember previously learned explicit memories

• sometimes temporarily disfunctional

• “going backwards”

• temporarily graded R.A.→ tend to have better memory for events and knowledge learned earlier in life

  • changing over time

  • not all but most temporally graded

  • worse for events/memories learned right before damage → better “further away” for damage

amnesia: explicit vs. implicit memory

• amnesia is associated with deficits in explicit memory

  • LTM → ex: episodic

• implicit memory is relatively spared

  • tend to perform normally on assessments of implicit memory

  • bc rely on other brain regions like BG & cerebellum

    • regions not damaged

H.M. (Henry Molaison)

• famous patient with anterograde amnesia

  • also have some reterograde amnesia (temporarily graded)

• spared (still functioning):

  • working memory/STM

  • implcit memory

• suffered w/ seizures

  • localized in temporal lobe → triggered by unknown activation

  • had brain surgery to remove hippocampus & MTL

    • successfully stopped seizures but cause AA & RA

  • shows role in explicit memory

• Tower of Hanoi task

  • evaluate implicit memory → procedure learning

  • can’t remember doing it → but got better bc of implicit memory

imagining the future

• amnesics have difficulty imagining the future

  • ex: what you would see while on camping trip → shows hippocampus is important for imaging future event

• evolutionarily → remembering our past can help us survive in the future

• learn from our past experiences

• predict what might occur in the future

dsexecutive amnesia

• memory impairments that result from frontal lobe damage

  • called “dysexecutive” amnesia bc frontal lobes perform high-level executive functions

dysexecutive amnesia impairments

• difficulty w/ strategic encoding & strategic retrieval

• greater difficulty w/ recall than recognition

  • longer than usual → ex: not recalling any words

  • overall harder in general

• impaired memory for temporal order of events

  • what are the order of events in the memory

• source amnesia → forgetting the context

  • individuals forgets context of where they learned something

  • forgetting source of info

• impaired metamemory → awareness of one’s own memory

  • reflecting on what memory you have/don’t have

  • bc individuals w/ DA struggle w/ executive functioning → effects awareness of own memory

• confabulation → making things up to try to make sense of the situation

  • w/ FL damage

  • “honest lying”

  • reason → making things up bc they don’t remember

• impaired working memory

  • heavily reliant on DLPFC

  • bc processes happen in damaged FL

dysexecutive amnesia: impaired recall

• recall is dependent on strategic, self-guided retrieval processes

  • using executive functioning to decide which memories to retrieve → damage making it harder

• frontal lobe damage makes strategic retrieval more difficult

• but spared performance on recognition test when self-initiated retrieval is not needed

  • bc hippocampus isn’t damaged

• lots of variability

  • ex: someone w/ hippocampal damage → can’t perform recognition or recall

case study: The Lost Mariner

• Korsakoff’s Amnesia

  • caused by chronic alcoholism & poor diet

  • severe thiamine deficiency

  • (sub)type of dysexecutive amnesia

    • related to brain regions outside of hippocampus (ex: FL)