week 7: memory 2 Flashcards
The multiple-trace hypothesis of memory classifies memory by duration:
Iconic memories are the briefest.
Short-term memories (STMs) are longer.
The most enduring form of memory is long-term memories (LTMs) which can last for days or years.
LTM categories
declarative
non-declarative (procedural)
what is Nondeclarative (procedural) memory
Things you know that you can show by doing (e.g., grammar, or motor skills, or problem-solving)
-unconscious memory (implicit)
what is Declarative memory
Things you know that you can tell others (e.g., facts and events)
-explicit memory (conscious memory)
Two subtypes of declarative memory
Semantic memory – generalised memory
Episodic memory – autobiographical
nondeclarative (procedurall) subcategories
skill learning (eg, bike riding)
priming (eg, being more likely to use a new word)
conditioning (eg, salivating when you see food)
Brain structures involved in learning and memory
central temporal lobes
Henry Gustav Molaison (H.M.)
suffered seizures
eeg showed abnormalities in central temporal lobes
Henry Gustav Molaison (H.M.) surgery
bilateral medial temporal lobectomy
removal of the medial portions of both temporal lobes including most of the hippocampus, amygdala and adjacent cortex (rhinal cortex).
HM results
Preserved perceptual and motor abilities
Preserved STM
Some retrograde amnesia
Severe anterograde amnesia
Anterograde amnesia
loss of memory after injury event
Retrograde amnesia
loss of memory prior to injury event
what formal assessments were conducted for HMs amnesia
Digit span + 1 test
Block tapping memory span test
Mirror drawing test
Incomplete pictures test
HM Digit span + 1 test results
Showed HM’s inability to form new long term memories for verbal information
Block tapping memory span test
HM results
Showed that his inability to form new memories was not just restricted to verbal information
Mirror drawing test
HM results
Despite not remembering the test, HM’s performance improved
Incomplete pictures test
HM results
Despite not remembering the test, HM’s performance improved
Incomplete pictures test
HM results
Despite not remembering the test, HM’s performance improved
Why was it so difficult to create an animal model of HM’s amnesia?
- wasn’t initially apparent that HM’s anterograde amnesia was specific to declarative (explicit) long term memories.
- incorrectly assumed that the amnesic effects of medial temporal lobe damage were largely attributable to hippocampal damage. Thus most efforts to develop animal models focussed on hippocampal lesions.
The delayed non-matching-to-sample task.
method for testing declarative memory in monkeys
what did The delayed non-matching-to-sample task provide
provided a means of testing the assumption that the amnesia resulting from medial temporal lobe damage is entirely the consequence of hippocampal damage
what does Bilateral surgical removal of the perirhinal cortex produce
produces severe and permanent deficits in performance on the delayed non-matching-to-sample test and other tests of object recognition
bilateral surgical removal of the hippocampus produces?
either moderate deficits or none at al
Bilateral destruction of the amygdala produces?
no effect on object recognition
Synaptic mechanisms of learning and memory trends
Structural changes at synapses
Physiological changes at synapses
Structural changes at synapses may include
Formation of new synapses
Rearrangement of synapses
Neurogenesis
Physiological changes at synapses may include
Long-term potentiation (LTP) (a stable and enduring increase in the effectiveness of synapses)
Long-term potentiation (LTP)
Repeated firing of a synapse lowers the threshold for that synapse to fire
Long-term potentiation (LTP) stages
Time 1 (before any change happens) Stage 2 (induction) Stage 3 (expression)
Time 1 (before any change happens) LTP
pre-synaptic neuron fires at a normal rate
post-synaptic neuron fires at a certain strength in response
LTP – Stage 2 (induction)
Time 2 (the cause of the change) pre-synaptic neuron fires a lot, causing post-synaptic neuron to fire a lot
LTP – Stage 3 (expression)
Time 3 (after the change)
- presynaptic neuron fires at a normal rate
- post-synaptic neuron now fires more strongly than it did at Time 1
Mechanisms of LTP
- The NMDA receptor is a receptor for glutamate
- the NMDA receptor does not respond maximally unless two events occur simultaneously
- NMDA receptors allow only small numbers of calcium ions to enter unless the neuron is already depolarised when glutamate binds to the receptors which triggers an action potential
what are the 2 events needed for the NMDA to respond maximally
- glutamate must bind to it
2. the postsynaptic neuron must already be partially depolarised
