Memory Systems Flashcards
Types of memory
- Declarative/explicit memory
- Nondeclarative/implicit memory
Declarative/explicit memory
- Localized to medial temporal lobe, especially hippocampus and diencephalon
- Facts and events
Nondeclarative/implicit memory
- Hard to learn, hard to forget
Procedural memory (localized to the striatum): skills and habits e.g. playing the piano
Classical conditioning (type of nondeclarative memory:
- Skeletal musculature (localized to cerebellum)
- Emotional response (localized to amygdala)
Declarative vs. nondeclarative memory
Declarative memory acts through conscious recollection – nondeclarative memories operate smoothly without conscious recollection
Declarative/explicit memory is localized to ___
Medial temporal lobe, especially hippocampus and diencephalon
Procedural memory is localized to the ___
Striatum
Skeletal musculature (type of classical conditioning) is localized to the ___
Cerebellum
Emotional responses (type of classical conditioning) is localized to the ___
Amygdala
Long-term memories
Can be recalled days, months, years after they’ve been stored and are only a fraction of what we experience
Short-term memories
Are vulnerable to disruption (head trauma, electroconvulsive therapy) that does not affect long-term memories
Memory consolidation
It is hypothesized that facts and events are stored in short-term memories and only a subset are converted to long-term memories through a process called memory consolidation
Suppose you were telling a friend about the amazing holiday cookie you ate the week before and you, ironically, trip on a large box of Girl Scout thin mints someone left on the sidewalk. You hit your head
and afterwards you are unable to recall the holiday cookie. Memory for the cookie was stored in what type of memory
a) Long term
b) Short term
c) working
B) short term
What is working memory?
An entirely different form of temporary shortage from short-term memories
Characteristics of working memory
- Only lasts for seconds
- Sharply limited in capacity and requires rehearsal ex. getting somebody’s
number - Commonly measured with digit span (max number of randomly chosen numbers read from a list that can be repeated back)
- More effectively held in mind through chunking (ex. breaking group of
numbers into meaningful groups (ex. 326-523-9843)) - Experimental evidence suggests digit spans in different modalities can be
separately damaged → there may be multiple temporary storage areas in the brain
How long does working memory last?
Seconds
Examples of experiments in working memory
- Delayed response task
- Identity & location tasks
Delayed response task
- Experiment Design: Monkey sees food be placed in one well → curtain closed for short delay period (monkey can’t see wells) → curtain reopens with wells covered → monkey chooses correct well with food in it
- What we learned: neurons in the prefrontal cortex showed activity during the delay period when the monkey must hold the information in working memory
Identity & location tasks
- Experiment Design: 2 types of tasks, identity and location tasks, where a participant must memorize the face or location of a face photo and then recall that after a short delay when tested
- What we learned: Delay-period activity found in different but overlapping areas for the two tasks → working memory delay activity exists at various brain locations depending on the task being done
What did the Delayed Response Task reveal about working memory?
a) Working memory is primarily stored in the hippocampus.
b) Neurons in the prefrontal cortex show activity during the delay period when information is held in working memory.
c) The task requires only short-term memory, not working memory.
d) The experiment showed that monkeys cannot retain information beyond a short delay.
B
What factors affect the consolidation process?
Salience and emotion
Consolidation of working and short-term memory
- Sensory info divided into working memory or short-term memory
- Short-term memory (hippocampus) is converted to long-term memory (cortex) through consolidation
- Working memory can apply things in long-term memory through retrieval
What structures does the medial temporal lobe include?
- Hippocampus
- Entorhinal cortex
Medial temporal cortex
- Includes hippocampus and nearby cortical areas such as the entorhinal cortex (functions as input to hippocampus)
- Critical for declarative memory formation and storage
Entorhinal cortex
Functions as input to hippocampus
Wilder Penfield - MTL
○ Procedure: electrical stimulation to the brain in epilepsy surgery
○ Found: Stimulation of temporal lobe → evoked more complex experiences (memories, traces)
○ Different response to stimulation than other brain regions
Human MTL recordings
○ Some neurons were sensitive to general categories like faces, buildings, etc)
○ Some neurons were highly selective to specific objects like Halle Berry’s name/face
○ Hippocampus seems to link new sensory information to older
Memory consolidation in brain regions
- Sensory info typically comes from association areas (NOT lower-level sensory areas)
- First reaches parahippocampal cortex and rhinal cortex (including perirhinal and entorhinal cortex)
3. Reaches hippocampus
a. Fornix is an important output pathway from the hippocampus: Loops around the thalamus before terminating at hypothalamus
b. Arrow from hippocampus to cortical association areas represents consolidation
Flow chart of memory consolidation in brain regions
Causes of amnesia
- Concussion
- Tumor
- Stroke
- Viral encephalitis
Two types of amnesia
- Retrograde
- Anterograde
Usually have some combination of both
Retrograde amnesia
- Forget past (retro) memories but can make new ones
- Usually graded in time (old memories more likely to be retained)
Anterograde amnesia
Unable to make new memories - cannot consolidate
Retrograde and anterograde amnesia graphs
Patient HM
- Treated for epilepsy – bilateral surgical removal of MTL (meaning parts of hippocampus, amygdala, and surrounding cortex)
- Resulted in absolute anterograde amnesia (no consolidation) and partial retrograde amnesia
- HOWEVER: still had intact working memory and intact procedural memory (could learn new tasks but not remember learning them)
- Clive Wearing – amnesia similar to HM, caused by viral encephalitis
What does Patient HM’s case indicate?
That medial temporal lobe not involved in storage of ALL memories: working memory and procedural memory probably mediated in other places as well
Which of the following are expected if Adrian had anterograde amnesia?
a) Forgets the first name of Dr. Paradiso
b) Remembers his mother’s maiden name
c) Can’t seem to recall that he texted Anna “nice weather huh” a week after his concussion
d) Can still remember how to ride a skateboard
b, c, and d
Which of the following best describes what was learned about memory from Patient HM’s case?
a) The medial temporal lobe is essential for consolidating new declarative memories and plays a central role in
storing working and procedural memories.
b) HM’s intact ability to learn new tasks demonstrates that the medial temporal lobe is not involved in memory formation.
c) The medial temporal lobe is required for declarative memory consolidation, but working and procedural memories appear to rely on other brain regions.
d) Damage to the medial temporal lobe results in complete loss of all memory types, including working, procedural, and declarative memory.
C
Experiments/evidence summary table
Hippocampus
- Memory consolidation
- Short-term memory
- Spatial memory
- Link information across sensory modalities
- Episodic and spatial memory may have the same basis, lesions affect both
Maybe:
○ grid & place cells = “where”
○ other temporal lobe cells = “what” we see
Together → hippocampal system can store “what happened where”
Models of memory storage
- Standard model
- Multiple trace model
Standard model of memory storage
- Linear, unchanged with retrieval
- Memory trace first made in hippocampus, then transferred to neocortex some time later
Multiple trace model of memory storage
- Patient HM – showed evidence of retrograde amnesia for decades (undermines standard model)
- Hippocampus & neocortex are both always involved in memory storage
- Each time memory is retrieved, new trace is added
Which statement best differentiates the standard model and the multiple trace model of memory storage?
a) The standard model posits that memories are stored exclusively in the hippocampus, while the multiple trace model suggests they are stored only in the neocortex.
b) The standard model proposes that memories are consolidated linearly in the hippocampus and then transferred to the neocortex, whereas the multiple trace model suggests that both the hippocampus and neocortex are involved in memory storage throughout its lifespan, with new traces added during retrieval.
c) The standard model states that retrieval creates new memory traces, while the multiple trace model views retrieval as leaving the original memory unchanged.
d) Both models agree that the hippocampus plays a minimal role in long-term memory retrieval
B
Reconsolidation
- Memories can be altered or even erased after consolidation
- Reconsolidation: recalling/ reactivating a memory makes it plastic (moldable) again
○ Can strengthen a memory if it has multiple recall events
○ Can alter the memory during its reconsolidation depending on activity during recall of memory - Important for adapting to new info
What is reconsolidation, and why is it important?
a) Reconsolidation occurs when memories are recalled or reactivated, making them plastic again, allowing them to be strengthened or altered depending on activity during recall.
b) Reconsolidation refers to the process where memories become permanently unchangeable after initial consolidation, making them resistant to further adaptation.
c) Reconsolidation is the process of transferring short-term memories to long-term storage without modification.
d) Reconsolidation is the erasure of old memories to make room for new information
in the hippocampus.
A
Impact of benzodiazepines on memory
- Benzodiazepines inhibit consolidation from HPC to cortex (ie: blocks memory formation)
○ GABAA receptor agonist (GABAA receptors inhibit neurons)
○ “Shuts down” hippocampus
○ Sometimes given during surgeries to block memory formation
○ Ex: Lorazepam, valium, rohypnol ■ Lorazepam study showed:
●reduced activity in hippocampus
● impaired memory task performance
● memory performance correlated with extent of activation in hippocampus
Altering memory: HDAC2 (histone deacetylase 2)
HDAC2 (histone deacetylase 2): shuts off plasticity genes → drugs that inhibit will turn on plasticity
Experiment:
1. Create traumatic experience for mouse by pairing a sound with an electric shock → mouse will freeze (fear response) whenever it hears the sound
2. Give mouse drug that inhibits HDAC2 (end result is plasticity will be turned on) and present sound in safe environment → animal will no longer fear foot shock (plasticity allows them to re-plasticize memory and make it non-traumatic)
3. Allows the rat to stop associating sound with pain
What does the experiment involving HDAC2 inhibition demonstrate about memory?
a) Memories cannot be altered once they are formed and consolidated.
b) HDAC2 inhibition prevents memory formation altogether, erasing traumatic memories instantly.
c) HDAC2 inhibition reactivates plasticity, allowing a traumatic memory to be re-plasticized and modified when presented in a safe environment.
d) Traumatic memories can only be erased through physical brain lesions, not through pharmacological methods.
C
A brain structure associated with procedural memory is
a) substantial nigra
b) cerebellum
c) striatum
c) striatum
A task used to test working memory is
a) delayed non-match to sample
b) Wisconsin card sorting
c) classical conditioning
d) instrumental learning
b) Wisconsin card sorting
When a mouse with a hippocampal lesion retrieves food from a radial arm maze, the mouse
a) no longer remembers the task
b) retrieves some of the food but never retrieves food from some of the arms
c) retrieves all of the food but repeatedly goes down arms from which it already got the food from
c) retrieves all of the food but repeatedly goes down arms from which it already got the food from
Which memory deficit might H.M. have had?
a) he forgets what his mother looked like
b) someone says a phone number and he can’t keep it in mind
c) he forgets how to drive a car, which he once knew how to do
d) he can’t remember the name of the scientist who studied him weekly over the past year
d) he can’t remember the name of the scientist who studied him weekly over the past year
Wilder Penfield was able to elicit bizarre memory-like experiences during epilepsy surgery when he electrically stimulated the ___ lobe
Temporal
Place cells in the hippocampus
- A place field is similar to a visual RF because a cell
responds most strongly when a rat sees or is near
one of several visual cues - If the rat is removed from the box, the box rotated,
and rat returned, the cell responds near the same
visual stimulus (not absolute location) - If the lights are turned out, the cell responds the same!
- Visual input is not essential
- The cell responds to the place where the animal thinks it is
In an experiment we discussed, rats formed a fearful memory of an electrical jolt to its
feet that was paired with a loud sound. What was the essential aspect of the experiment that
appeared to erase the fearful memory the day after the fearful memory was formed?
a) The memory was reactivated a day later by the loud sound and electroconvulsive shock (ECS)
was administered but no foot shock
b) A day later, the rat was returned to the cage where the fearful memory was formed, but there
was no foot shock, loud sound, or ECS
c) A new non-fearful memory was formed the next day by giving the animal ECS in the original
cage without the loud sound or the foot shock
d) The loud sound was played the next day without the foot shock while a protein synthesis
inhibitor was administered
a) The memory was reactivated a day later by the loud sound and electroconvulsive shock (ECS)
In the MTM, memories are stored in both the ___ and in ___
Hippocampus and neocortex
Fondly retrieving the name of your
long-gone goldfish “Mr. Glubs” probably involves moving information
a) From long term memory to working memory
b) From short term memory to long term memory
c) From working memory to short term memory
d) From long term memory to short term memory
a) From long term memory to working memory
Declarative memory consolidation is significantly impacted by lesions in all of the following structures except:
a) prefrontal cortex
b) thalamus
c) hippocampus
d) parahippocampal and rhinal cortex
a) prefrontal cortex
Where is it thought that memory consolidation occurs?
Hippocampus
The primary source of input to the hippocampus comes from ___
entorhinal cortex
