Lecture 9 - Episodic and Semantic Memory Part 1 Flashcards
What is the definition of episodic memories?
● “Episodic memories: Consciously retrieved memories of unique events, bound by event specific contextual details, such as the time and place in which the experiences occurred.”
AKA unique events in time and place (like last birthday party)
What is the definition of semantic memories?
● “Semantic memories: Consciously retrieved knowledge of autobiographical and non-personal concepts or “facts.” Semantic memories are derived from experience but are largely retrievable without reconstructing specific details about the contexts from which they were extracted.”
AKA knowledge or facts. (what is the date of your birthday. What is the capital of canada?)
What is the category that episodic and semantic memory fall into?
declarative memory
this falls under declarative memory. Within long term memory we have declarative memory, we are consciously aware of things from our lives. We also have non-declarative memories. These might not be consciously retrievable to us but they have changed how we live our lives.
Whats an example of how episodic vs semantic memory works?
● Most students do not remember when and where they first heard about Paris as the capital of France…(episodic)
● …But, most students know that Paris is the capital of France (semantic)
● These forms of memory are highly relevant in humans but…
Can non-humans have episodic memories?
● Some researchers believe that animals cannot maintain episodic memories; others hold the opposite view
○ Birds may be able to remember specific events and how long ago they happened
○ Do we think this is episodic memory?
lots of research has been done in rodents, birds, and other species. If we think it is the same memory system, we can generalize better to humans. People in the field disagree a lot about whether or not non human animals have episodic memory.
how do we know that is not a conditioned response?
this experiment is really famous in psych because it provides the closest evidence of episodic memory in non-human animals.
● Scrub jays hid either worms (which spoil over time) or nuts (which do not spoil quickly) in different parts of a sand-filled ice tray.
● Later, the scrub jays were given the opportunity to retrieve the food
● If the delay was short, scrub jays preferentially retrieved the worms. If the delay was
longer, scrub jays retrieved the nuts. It was as though they anticipated the quick
spoilage of worms.
● Some believe that this behaviour is evidence that the scrub jays possess episodic
memory:
○ They seemed to remember what food they hid, where they had hid it, and how long since they hid it (when).
in this experiment, the researchers used ice trays filled with sand. They are trained to hide their food in the little compartments. They hide the nuts in some places and the worms in others, later on, when they have the opportunity to retrieve their food, what do they do? If the delay was short the scrub jays would unbury the worms, if the delay was long, they would grab the nuts. The idea was that they were afraid that the worms would spoil. Some say that this is evidence of episodic memory.
people use the term episodic like behaviour for this because people disagree. We’re not sure its the same type of episodic memory humans have but it gets close.
someone said that animals are missing autonoetic consciousness. He said there is a special kind of consciousness that humans have that allows us to rexperience our past, we can relive our past in our minds eye. We have a sense of self and know our own memories belong to us. Some researchers believe that humans uniquely have certain forms of consciousness. This is a really debated area of research.
What is Amnesia?
● “The amnesic syndrome: a profound impairment in the ability to store and retrieve consciously experienced, long-term memories in the context of otherwise relatively spared cognition. The prototypical amnesic syndrome is caused by acquired, stable damage to the extended hippocampal network.”
● Episodic memory is most severely impaired.
you can call it amnesia as well. In short, this is a loss of certain forms of longterm memory. Especially episodic memory. There is a lot of debate around the extent of semantic loss. Ex: you meet a patient, leave the room and come back, they won’t remember woh you are because they won’t be able to hold on to that memory of you. We use the term relatively spared cognition because there is debate about how intact everything else is. The important takeaway is that the episodic memory impairment is so striking that the other levels of impairment are unmatched compared to the severity of the episodic impairment.
What can cause amnesia?
● Multiple etiologies can cause amnesia:
○ stroke
○ virus (e.g., encephalitis) (a virus can affect the brain that can cause swelling (can be from a mosquito bite) you can take antiviral medication that can spare you from the damage. )
○ anoxia/hypoxia (reduced or complete loss of oxygen)
(this is a reduced or complete loss of oxygen. Know the term anoxia is the severity of oxygen deprivation. It refers to a loss of oxygen for some temporary period of time. you want the oxygen deprivation to be as short as possible. )
○ traumatic brain injury
(these tend to be less focal in nature so ex from a car crash or getting hit in the head it can impact more than one part of the brain)
○ surgical resections (for tumors or epilepsy)
(particularly in the case of HM because he has both of his hippocampi removed. A long time ago tis used to be done bilaterally, now it is done unilaterally. Epilepsy itself can damage the hoppocampus. this is less but when the tissue is removed, thats when you can see amnesia. )
how does one get amnesia? there are multiple causes. Stroke severe loss of episodic memory tend to come from strokes that impact the hippocus. Often bilaterally.
● Many of these illnesses, diseases or injuries affect the whole brain but the hippocampus (as we will see) is especially sensitive. For example in anoxia, the hippocampus is more vulnerable due to its high metabolic demand (it constantly needs a lot of oxygen). Other cellular properties can lead to toxicity effects in the hippocampus following anoxia.
● The hippocampus is also vulnerable to seizure activity
What are the types of amnesia?
Many forms of amnesia are permanent but there are temporary variants, which involve profound memory loss for a short period of time
○ Transient global amnesia
■ Causes unclear but several candidates
○ Psychogenic amnesia (extends to loss of identity) ■ Linked to psychological factors (e.g., stress)
there is some evidence that for this time period, the hippocampus is not focusing as it should.
most forms of amnesia are permanent but there are 2 types that are temporary.
this looks like permanent amnesia but it doesn’t last as long. There is another form called psychogenic amnesia that extends to loss of identity. This is when someone wdoes not know who they are. Every other form of amnesia, the people who experience it know who they are still. This can resolve and they go on in their lives but this can be precipitated by a very traumatic experience. For the period of time when they were amnesic, they don’t remember much from that time.
What do we know about Clive Wearing?
shes asking him about music and he says he’s never heard a note in his life.
his is one of the most severe forms because the damage to his brain is quite widespread. Whats interesting in patients is that through lots of repetition, they can learn things like knowing that he got sick. Whats interesting is his memory loss and his ability to play the piano.
he still knows who he is, he knows his wife.
Amnesia Data: Patient H.M.
(the most studied mind in history)
“Every day is alone in itself, whatever enjoyment I’ve had, and whatever sorrow I’ve had…Right now, I’m wondering. Have I done or said anything amiss? You see, at this moment everything looks clear to me, but what happened just before? That’s what worries me. It’s like waking from a dream; I just don’t remember” (H.M.)
-Milner (1970, p37).
the remainder of the calss we will talk about what is spared and not based on the extend of damage.
● Seizures originated in medial temporal lobes (MTL) including hippocampus (H) ○ We will learn more about these regions later in this lecture
● 1953: William Scoville removed MTL bilaterally
Hm had seizures that originated in his hoppocampus and doctors opted to remove the tissue because medication wasn’t working for reducing the seizured. They removed his hippocampus bilaterally.
We will talk more about the anatomy in the last section of today’s lecture
What happened to HM post surgery?
● IQ unchanged (118)
● Relatively intact short-term memory (more on this later)
● Relatively intact perception attention, language
● But…complained of severe (long-term) memory loss
● Referred to Brenda Milner, neuropsychologist
this surgery is only done unilaterally now.
after his surgery his IQ was relatively unchanged, he had relatively in tact short term memory. Clive’s video talks about the demand of the 7 second memory. Most patient’s short term memory is 20-30 seconds.
What is the difference between episodic and semantic memory in amnesia?
● When H.M. was asked about his past (before his surgery) he could remember facts about himself and the world but could not remember any specific events.
● Suggests that damage to the hippocampus affects episodic memory but less so semantic memory?
○ Depends on whether you are examining pre- versus post-amnesia information and what types of tests you use!
○ Let’s summarize some patterns together
What is the anterograde domain in anterograde amnesia?
What is the retrograde domain in retrograde amnesia?
Memories derived from experiences that occurred after the onset of amnesia-driving.” (anterograde amnesia)
● “Retrograde domain: Memories derived from experiences that occurred prior to the onset of amnesia. (retrograde amnesia)
anterograde and retrograde amnesia cooccur in most patients. Having just one is incredibly rare. In most patients, they have both. The way it presents is a bit different. Anterograde and retrograde amnesia cooccur in patients.
when talking about new learning, we say anterograde. We want to test patients on their memory for stuff they learned after the onset of amnesia. When talking about anything that occured prior to the onset of amnesia we are talking about retrograde.
A cautionary note: students often find these terms confusing because they mistakenly believe they refer to two syndromes that do not co-occur. In fact a single patient can have BOTH retrograde and anterograde amnesia (many do!
Anterograde vs retrograde amnesia? WATCH THIS PART OF THE VIDEO
Patients with amnesia like H.M. have
profound impairment in remembering events from their pre-injury life (episodic memory impairment) but they have relative sparing of semantic memory (they know things about their life)
Patients with amnesia like H.M. have profound impairment in learning/remembering episodes from their post-injury life and they have problems learning new facts (semantic memory)
Childhood (retrograde amnesia)
time of injury
Present (anterograde amnesia)
● Patterns of loss in anterograde amnesia is relatively undisputed amongst scholars.
● But scholars differ in their opinions on retrograde amnesia for many reasons, but let’s start with just one).
● We use the term “relative” sparing to denote that though semantic memory is much better than episodic memory but not always intact.
most of us agree on what happens to new learning.
Does dissociation preclude association?
Semantic and episodic memory can dissociate to some extent following a brain injury. However, in the healthy brain, they often interact.
Example 1: When you are cooking a recipe for the second time, you may remember some of the ingredients and steps (semantic memory) but you may also have an episodic memory of that first instance, which helps you refine your memory of the steps
Example 2: When you recall a memory of your professor tripping and falling, you include the specific episodic details (her loud scream), but also use your general knowledge (semantic memory) to “fill in” the gaps (professors always stand at the front)
What is the anatomy of declarative memory?
● The medial temporal lobes in humans contain the hippocampus and nearby cortical areas, including the entorhinal cortex, the perirhinal cortex, and the parahippocampal cortex (called “medial temporal lobes” or ”MTL”)
most of the patients we talk abotu have damage to the hippocampus, some have damage to the cortex.
How does the hippocampus relate to episodic memory? What evidence is there of this?
● Much research points to the role of the hippocampus in episodic memory especially.
● Began with H.M.
● Similar pattern observed in many other patients
● What other evidence points to a role of the hippocampus in episodic memory?
● Many fMRI studies show strong activation in the hippocampus during episodic memory tasks.
● Its activation occurs for both the encoding and retrieval of episodic memories.
Taken together, there is strong evidence from patient work and fMRI that the hippocampus (and MTL) are involved in episodic memory
● But what exact role does the hippocampus play?
● Even within episodic memory, though researchers agree that the hippocampus is important for new learning (anterograde). There is disagreement about the role of the hippocampus in old episodic memories (retrograde)
Do researchers agree on retrograde amnesia?
No
do researchers agree on anterograde amnesia?
yes
