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Ways to carve up memory into different parts or systems:
By duration of storage Sensory vs Short-term vs Long-term
Divisions of long-term memory: Episodic vs Semantic and Declarative vs Nondeclarative
Types of memory deficits:
Organic memory deficit: a deficit which is definitely caused by brain damage
Domain-specific deficit: memory deficit that is restricted to one sort of material such as faces but not verbal material, verbal material but not faces)
Domain-general deficit: Memory deficits that affects all sorts of material
Anterograde amnesia:
Difficulty learning new material AFTER the brain damage. All amnesic patients have anterograde amnesia. So its very difficult to learn new material with anterograde amnesia
Retrograde amnesia:
Difficulty remembering material that was learned BEFORE the brain damage, Most amnesic patients have retrograde amnesia. So it's very difficult to remember old material in retrograde amnesia
Ways to get brain damage that creates amnesia:
Stroke (disruption of blood flow)
Viral infection of brain (encephalitis) o Brain surgery to correct some other problem (remove tumor, remove epileptic tissue, etc)
Head injury (car wreck, gunshot, etc). Luckily with head injuries many have Post-traumatic-amnesia which is often temporary and does not last very long
Degenerative disorders (Alzheimer's disease, etc)
What are the two key brain areas in which damage to these areas will cause amnesia?
The Anterior Thalamus and the Medial Temporal Lobe
What do the Anterior Thalamus and the Medial Temporal Lobe have in common?
These two parts of the brain both link many different parts of the cortex together. So the medial temporal lobe is getting information from all the sensory modalities and is sending out many aspect of information as well.
The Anterior Thalamus is also doing the same thing, having many different connections to many parts of the cortex
Why is damage to the interior thalamus rare?
Damage to the interior thalamus is rare without damaging other parts of the brain.
What is the first part of the brain to deteriorate during alzheimer's?
The interior thalamus is the first part of the brain to degenerate during alzheimer's
The case of HM:
HM had a Severe seizure disorder from an injury when he was 10. At age 27 he had surgery to remove both hippocampi, which is the area of the brain responsible for memory. After that, unable to form new memories of the sort we normally think of as "memories" as he now had anterograde amnesia.
He no longer remembered people he met after surgery, he could No longer learn new words in his vocabulary and had No knowledge of public events or really any new information after surgery. So he could not remember his new address nor the death of his mother
Did HM have STM?
Yes HM did have STM but had both anterograde and retrograde amnesia. But this retrograde amnesia is only for information that occurred a few months before the event
What sorts of learning are impaired in amnesic subjects?
Declarative memory: Amnesic patients often have difficulty forming new declarative memories, which are conscious memories for facts, events, and personal experiences. This includes both semantic memory (general knowledge) and episodic memory (personal experiences).
Episodic memory: In particular, anterograde amnesic patients struggle to form new episodic memories, which are memories for specific events and personal experiences. For example, they may have difficulty remembering what they ate for breakfast that morning or where they went yesterday.
What sorts of learning are intact in amnesic subjects? Be able to provide examples of different varieties of spared learning:
Procedural memory/Perceptual-motor skill such as mirror tracing: Amnesic patients can often learn new motor skills, such as riding a bike or mirror tracing, even if they have no conscious memory of learning these skills.
Perceptual Priming: Patients with medial temporal amnesia will still be able to recognize line segment pictures if they saw the full image. Amnesic patients, when given two letters like "Mo" are more likely to say the word "Moter" if they were exposed to this word before hand, even if they do not remember seeing this word
Classical conditioning: Can be demonstrated by sending a puff of air at an eye while hearing a sound, which will cause the eye to blink. But when they hear the sound again they will blink even without the air
What's the evidence that retrograde amnesia is time-limited?
A study found that memories that occurred quite recently before amnesic brain damage occurred were not remembered very well, but that memoirs that were from years and years from when the brain damage occurred were still remembered quite well, as well as a control group.
This shows that retrograde amnesia is time limited and is not all encompassing, but instead only occurs with information that happened close before the brain damage. They found this to be the case with both autobiographical memories as well as cultural memories
Are new or old memories more susceptible to damage to the temporal lobe?
Newer memories are more susceptible to damage to the medial temporal lobe, while the older memories do not seem to require the medial temporal lobe anymore
Factors of medial-temporal amnesia:
Short-term memory is normal while new learning is impaired due to anterograde amnesia
Long-term memories acquired some weeks to a few years before brain damage are impaired which is an example of retrograde amnesia while very old memories are OK as a result of retrograde amnesia being time-limited
How is the medial temporal lobe thought to be involved in memory consolidation?
The medial temporal lobe which is where the hippocampus is, is not where STM is stored due to STM being normal in medial temporal amnesic. This also shows that the medial temporal lobe is not the storage site for all memories as very old memories are normal in retrograde amnesiacs.
But we can determine that the medial temporal lobe has some function in helping memoires become permanent. This is the consolidation theory of medial temporal lobe function in memory
Consolidation theory of the Medial Temporal Lobe:
Memories are initially formed in both the Medial Temporal Lobe and in other parts of the cortex. And that these newly formed memories in the MTL are strong while those in other parts of the cortex are weak.
But over time output from the medial temporal lobe helps train other parts of the cortex to strengthen memoires in those areas. So it helps memories become permanent
Medial temporal binding idea:
There are going to be a ton of different components to a memory, from auditory information, to verbal information, to how you're feeling about the memory, to a lot of other aspects of the memory. So there are different parts of the brain processing different parts of the event.
But there are many parts of the cortex connected to the Medial Temporal Lobe. These neurons that were initially active in the medial temporal lobe have strong connections with each other now, so if there is a retrieval cue, that reminder will activate the relevant clump of neurons in the Medial Temporal Lobe, but they will also activate the other neurons that are connected to the neurons in other parts of the cortex.
So the medial temporal lobe trains the other areas of the brain to form connections between them. So eventually you can cut the medial temporal lobe out of the picture for these memories that have already been consolidated as they have been trained to activate.
What are the part of the brain that stores specific types of information?
The part of the brain that handles that information is also storing the memory, so for the motor skills the cerebellum is needed for classical conditioning, while classical conditioning of emotions is in the amygdala
What actions do not rely on the medial temporal lobe?
Perceptual priming, classical conditioning and perceptual motor skills all do not rely on the medial temporal lobe.
Areas of the brain that are impaired in amnesic patients vs those that are preserved:
IMPAIRED in amnesics: New episodic or semantic learning
PRESERVED in amnesics: Simple classical conditioning: Eyeblink conditioning
Perceptual learning: Word-stem completion, recognizing fragmented pictures
Skill learning: Perceptual-motor: Mirror-tracing Cognitive learning: puzzle tasks, artificial grammars
Can amnesics improve on cognitive skills and if so what are some examples of things they can improve on?
Amnesics do not only improve on motor and perceptual skills but there is also proof that they improve on cognitive skills such as on the tower of london problem.
Amnesic patients also can learn the order of Phrase structure of a language, meaning the order of words and grammar of the words. But they can't learn a foreign language as they would have to learn the vocabulary of a language which is not preserved in amnesic patients
What is some proof amnesics can learn cognitive skills?
Amnesics can acquire artificial grammar which is proof they can learn cognitive skills
What are the 4 things the MTL does that supports declarative memory?
Conscious awareness of the memory
You learn quicker with the medial temporal lobe than without it
The medial temporal lobe provides flexibility of the acquired knowledge, so it can be used in other tasks
The medial temporal lobe relates all the information in a memory together
Consciousness of memory with the medial temporal lobe providing future planning:
Having access to the medial temporal lobe provides you with the ability to replay events, which is helpful for future planning, by allowing you to think of alternative outcomes to events. So the medial temporal lobe is important for planning for the future.
Quicker learning in the medial temporal lobe:
So in some cases you only need a few instances of training as opposed to a lot training when you have access to the medial temporal lobe. So it helps with rapid learning.
EP and GP study Severely amnesic participants were given pairs of simple objects and they pick one of them.
Under one item it says correct, so the next time they go through the objects they would have to see if they could choose the correct item again. In normal people it took them around 3 days to get it basically perfect.
In these amnesic patients, it took them incredibly longer, almost 36 days to get to a good accuracy level. So this proves that the medial temporal lobe increases the speed of learning.
The flexibility aspect of the EP/GP study:
The flexibility part of the experiment had all the items on the table instead of in pairs and they were asked to sort the items into correct and incorrect categories.
They found that people with a functioning medial temporal lobe were able to put all the items into the categories, meaning their learning was flexible enough to transfer skills from one task to another task, while EP and GP were not able to transfer these skills over, demonstrating that there was very little flexibility
Discuss how rats with damage to the medial temporal lobe do not have the flexibility to transfer information from one task to another:
Found that rats with brain legions can learn a task such as a goes to b and b goes to c, but they cannot translate that to simply that a goes to c.
This is an example of damage to the medial temporal lobe resulting in a lack of flexibility of knowledge, as the rats could not translate their knowledge from one task to another
Why is it important that the medial temporal lobe provides flexibility to learning?
You need the medial temporal lobe to be able to apply information from one task to another
What does the medial temporal lobe do in terms of relating content together in memory?
The medial temporal lobe relates all the information in a memory together. So if you have the word captain, you can remember all aspects of captain from what it means to what a captain looks like.
A person with damage to the medial temporal lobe will have the word captain and only see the word captain, not being able to connect it to it meaning or potential imgadry of a captain.
What might be the GENERAL difference between the sorts of learning that are impaired versus intact in amnesia?
While explicit learning is generally impaired in amnesia, implicit learning can often remain functional
