Memory Flashcards
Lecture 11
how is memory affected by retrograde amnesia?
- person can create new memories but forgets old ones
- can be temporally graded, remember super old memories but not more recent ones before injury
how is memory affected by anterograde amnesia?
person can’t create new memories but remembers old ones
who is patient HM
- had bilateral medial temporal lobes removed because of severe epilepsy (hippocampus, amygdala, part of temporal cortex)
- developed anterograde amnesia and had temporally graded retrograde amnesia
- but working memory was intact
what were patient HM’s symptoms (how did he perform on tasks)
- had severe anterograde amnesia but short term and working memory were intact
- could perform a digit span task with 6-7 digits
- but, when asked to remember things that can’t be actively rehearsed and repeated, he couldn’t (picture matching)
- got better at tasks they did multiple times, but had no memory of doing the task in the past
what was patient HM’s memory duration like?
- they had working (short-term) memory, and could learn motor skills
- they could not consolidate memory into long term storage
what is implicit vs. explicit memory?
- implicit memory - things we remember without being conscious of it
- ex. learning to ride a bike
- explicit memory - things that require effort to remember, need to be actively recalled
- ex. general facts about the world
what are the two types of explicit memory?
- episodic memory - personally experiences events
- semantic memory - facts and general knowledge
who is patient KC?
- had bilateral hippocampus lesions
- remembered general facts but couldn’t remember experiences he had
- semantic memory was intact but episodic memory was not
what is the hippocampal indexing theory?
- all sensory information and stimuli from the event gets indexed together in the hippocampus
- indexing required at first in order to generate recall from other areas
- connections are strong and are able to be associated with each other even without the hippocampus
what is long term potentiation?
- repetitive strengthening of synapses that enables a long-lasting increase in synaptic transmission
- performed in the hippocampus of rats
- use weak vs. strong stimuli and measure EPSPs via electrodes to create a strong neural connections
what happens during long term potentiation?
- EPSP causes glutamate to release into the synapse and bind to AMPARs and NMDARs
- magnesium blocks in NMDARs require a very strong positive charge/depolarization in order to open and allow sodium in
- stronger signals = more calcium = more AMPARs go to bind to more glutamate
- more sodium and calcium are let in for a stronger connection
what are the immediate short term changes (functional) associated with LTP?
AMPARs are recruited to the membrane to have more signals and stronger connection between neurons
what are the long-lasting, slower changes (structural) associated with LTP?
- it can make synapses stronger and able to make more connections
- can start second messenger signalling and changes in genes to create more AMPARs
- ability for stronger memories
how and why are NMDARs related to brain dysfunction?
- LTP is more prominent in memory-related areas
- also epilepsy because of excitable brain areas
- NMDAR activity allows calcium into the cell
- calcium is a potent signalling molecule but too much can trigger apoptosis
- alcohol, PCP, ketamine are NMDAR antagonists
- lose abilities to form memories
what is alzheimer’s disease?
- irreversible (no cure), progressive, neurogenerative disease
- most common cause of dementia
- appears first in the medial temporal lobe then progresses to the cortex
- occasional early onset (familial or genetic form of AD) but there is no single gene associated with AD
