Long-term memory and learning Flashcards
Where is the hippocampus located? (name the region, nearby anatomical structures etc.)
In the allocortex, within the medial temporal lobe near e.g. amygdala
What part of Henry Molaison’s (HM) brain was removed? What were HM’s symptoms after the resection? What was intact?
Half of the hippocampus, 5cm of the medial temporal lobe were removed (bilaterally); the more posterior part of the hippocampus was left in place. Remaining hippocampus atrophied.
Symptoms:
Anterograde loss of declarative long-term memory
Minor retrograde loss of declarative memory (long-term memory intact up to 2 years before surgery)
Intact:
IQ, perception, short-term memory unless distracted, procedural memory
Describe the concept of systems-level consolidation.
Hippocampus learns a pointer to individual items in sensory areas, then initially, in the consolidation stage, you have a retrieval cue sent to the hippocampus and the hippocampus retrieves the pointers to the individual entities that are stored throughout the cortex. Later, a fully consolidated memory is then retrieved from the cortex directly.
Name 2 subtypes of declarative (explicit) memory
episodic memory, semantic memory
Name at least 2 subtypes of non-declarative (implicit) memory
procedural memory, perceptual memory, classical conditioning, non-associative learning
Name the 4 stages of memory
encoding, consolidation, storage, retrieval
Name some key brain regions active in declarative memory
- Medial temporal lobe (esp. hippocampus)
- PFC
- middle diencephalon
Perceptual priming is an example of what kind of memory?
non-declarative (implicit) memory
Give an example of a procedural memory. Which areas do you expect to be involved?
Learning an action or a skill, like riding a bike, juggling, etc.. Involvement of basal ganglia, cerebellum and others dependent on the task.
What is some the evidence for the “fragility” of the consolidation stage?
“Concussed football players (N = 6) were interviewed immediately after injury and were then found to possess good recall for events that had occurred just before the injury. Within 3-20 min, however, recall for these events was lost. Such delayed forgetting did not occur in a control group of 12 players who suffered injuries other than concussion.”
This shows that consolidation is needed for storage to LTM, and can be disrupted.
There are two criteria of distinguishing long-term memory.
hippocampus dependence, resistance to distraction
what is Ribot’s law?
It states that there is a time gradient in retrograde amnesia, so that recent memories are more likely to be lost than more remote memories.
Is long-term memory always dependent on the hippocampus?
no (according to the systems-level consolidation model), over time (remote memories) becomes hippocampus-independent and stored in cortical associations
Transfer of memories from hippocampus to neocortex possibly occurs when the neocortex is not processing external stimuli. Explain.
One example is a study by Pavlides & Winson (1989), where the place cells of rats (encoding where they have been recently) fired the most during sleep. The interpretation is that the way in which you consolidate information is in a sleep offline stage, since you don’t have new information coming in. By sleeping you can turn off the inputs and allow the hippocampus to replay the memory
Procedural learning depends on the MTL. Yes/No?
No. HM showed good progress on procedural learning tasks and could form new procedural memories.
