Learning and Memory 1: Hippocampus Flashcards
What did HM have done? Effect?
Bilateral medial temporal lobectomy. Anterograde amnesia (couldn’t form new memories) due to loss of hippocampuses.
What’s the difference between declarative and non-declarative memory?
Declarative - something that can be put into words
Non-declarative - behavioral change in response to stimulus
What is episodic memory?
“Autobiographical” memories - of scenes, context, etc. Emphasis on being from personal experience. (E.g. remembering watching Barack Obama’s election)
What is semantic memory?
Factual knowledge. Remembering that Obama’s the president, scissors are for cutting, the symptoms of Walenberg syndrome, etc.
What is familiarity?
The sense that you’ve seen something or someone before. Loss of familiarity may lead people to think family members have been replaced by imposters.
What is recollection?
Related to familiarity and episodic memory, it’s when the “flood of context” associated with, for example, a person and why they are familiar to you comes into conscious thought. (“Oh! He was in that movie with Kevin Bacon…”)
What are the 3 stages of processing of episodic memory?
Encoding, storage/consolidation, retrieval.
What are the 3 parts of the hippocampal formation?
Subfields, dentate, subiculum.
What are 3 extrahippocampal medial temporal structures?
Entorhinal cortex, parahippocampus, and perirhinal cortex.
Do the medial temporal lobes receive input from multiple sensory modalities?
Yes.
What process allows you remember your night out just from hearing the name of the bar? What structure seems to be particularly important for this?
Binding. The hippocampus - takes input from multiple sensory modalities and forms associations.
What extrahippocampal medial temporal structure is involved with the “what?” (ventral visual pathway) for object memory?
The perirhinal cortex.
What extrahippocampal medial temporal structure is involved with the “where?” (dorsal visual pathway) for spatial/contextual memory?
The parahippocampus.
A lesion to what structure might cause you to specifically lose familiarity?
Lesion to the perirhinal cortex.
A lesion to what structure might give you problems with recollection? (linking the familiarity with the context)
The hippocampus.
What is Capgras delusion/syndrome? What is it often associated with?
Distortion of familiarity -> thinking family member has been replaced by an imposter. Occurs in Alzheimer’s.
What’s Fregoli syndrome?
Another disorder of familiarity, but here you think everybody is familiar (or even that a stranger is embodying a friend/family member)
What pathological process can cause Deja Vu?
Medial temporal lobe seizures.
Review: What structures are in the Papez circuit? What happens if you lesion a part of it?
Fornix, mamillary bodies, anterior thalamic nucleus, posterior cingulate/retrosplenial cortex.
Lesions result in amnesia similar to hippocampal lesion.
What’s one notable lesions to the Papez circuit? Specific structure affected? Effects on memory? Underlying cause of disease?
Wernicke-Korsakoff Syndrome. Lesion to mamillary bodies. Both anterograde and retrograde amnesia. Thiamine deficiency (most often associated with alcoholism).
What is Ribot’s Law? When does it apply?
recent memories are more likely to be lost than the more remote memories in retrograde amnesia *updated
Creates a temporal gradient of amnesia in hippocampal / temporal-limbic amnesia. (doesn’t apply when there’s more extensive medial temporal lobe / neocortex involvement)
Do lesions that affect episodic memory affect semantic memory?
Yes. (and if they’re hippocampal, the retrograde memory loss follows Ribot’s Law, i.e. has a temporal gradient)
If a patient performs much better memorizing a list when asked to visualize the items vs. “unconstrained free recall”, where might the lesion localize?
Frontal lobes - which appear to be important for spontaneous encoding / retrieval of memories.
Lesions to what area might increase false memories or memory distortions?
Frontal lobes
Major differences between amnesia from medial temporal lobe vs. frontal lobe lesion? (2-3 things)
Frontal lobe amnesia is improved with cues and environmental (contextual) information. Frontal lobe lesions have a high tendency for false memory.
How can testing memory of word lists discriminated between storage and retrieval deficits?
If patients can get it with multiple choice, it’s primarily retrieval. If they can’t, it’s primarily storage.
Might the lateral parietal lobes be involved with memory?
Yeah… they might be….
What is the concept of “reactivation” apply to recalling memories of objects?
Sensory areas of the modalities in which the object was initially introduced are more strongly reactivated upon recall. (E.g. if you saw a picture of a hammer, your visual areas will light when asked to think about a hammer; if someone plays a sound of hammering, your auditory centers might light up when later asked to think about a hammer)
What are the two main pathological features of Alzheimer’s Disease (AD)? Which one is more proximal in the disease process?
Amyloid plaques - more proximal
Neurofibrillary Tangles - more indicative of severe disease
What are amyloid plaques?
extracellular A-beta fragment of Amyloid Precursor Protein.
What are neurofibrillary tangles?
Intracellualr, paired helical structures made of hyperphosphorylated Tau.
What percentage of AD cases are considered sporadic? (genetically speaking)
95% ish
What do all the genes associated with autosomal dominant AD inheritance have in common?
All associated with processing of amyloid precursor protein.
How does AD memory loss contrast with the normal memory loss of aging?
Memory using environmental context should be spared in memory loss of aging, but is not in AD.
How does AD cause amnesia? How can it be seen with imaging?
Damage to the hippocampus and extrahippocampal structures. Progressive atrophy can be seen on MRI.
Why shouldn’t people with AD take scopolamine for sea-sickness?
Scopolamine is anti-cholinergic. ACh signaling appears to be necessary for memory formation, and people with AD are particularly susceptible to anti-cholinergic treatment.
What drugs can be used to improve memory in AD? (2 types)
Cholinesterase inhibitors (-stigmines, Aricept, others) NMDA antagonists (memantine)
