Memory

Question 1

Declarative Memory - Encoding

Answer 1

Encoding is the process of establishing a memory

Features are remembered in the same brain sensory and motor areas involved in encoding.

Relationship among the events that bind them together as a single memory (“index”) is stored in the medial temporal lobe.

Question 2

Declarative Memory - Storage

Answer 2

Memories are strengthened or “consolidated” during a storage phase.

Makes them long lasting and perhaps permanent.

Some memories may not be strengthened, resulting in forgetting

Question 3

Declarative Memory - Retrieval (recent memories)

Answer 3

Retrieval is the process of recalling a memory

An internal or external cue is used to trigger voluntary or involuntary retrieval

In recent memories the cues act by accessing the index in medial temporal lobe

Temporal lobe serves to coordinate information in cortical regions

Question 4

Declarative Memory - Retrieval (old memories)

Answer 4

Retrieval is the process of recalling a memory

An internal or external cue is used to trigger voluntary or involuntary retrieval

In remote or old memories the cue can access the cortical circuits directly.

Memories can be retrieved without access to medial temporal lobe

Question 5

Role of Frontal Lobe in Declarative Memory

Answer 5

Frontal lobes play a role in the semantic and linguistic processing important for encoding and retrieval.
connecting information with existing knowledge.

Guide search and evaluate search results

Also play a role in working memory

Question 6

Role of Parietal Lobe in Declarative Memory

Answer 6

Important for attentional processes

Directing attention appropriately for the encoding and retrieval of memories.

Question 7

Anatomy of medial temporal lobe

Answer 7

Hippocampus
Parahippocampal cortex
Rhinal Cortex (Perirhinal / EntoRhinal)

Question 8

Medial temporal lobe connectivity

Answer 8

The perirhinal and pararahippocampal corticies receive input from unimodal and polymodal associated areas in the cortex.

They project primarily to the entorhinal cortex
Entorhinal cortex in turn projects to the hippocampus.
Hippocampus is well positioned to integrate information from multiple cortical regions into a single memory or event.

Question 9

Cognitive map theory (hippocampus)

Answer 9

Hippocampus plays a role in memory for the spatial relationship among items.

Existence of place cells in rodent and human hippocampus.

Experienced taxi drivers have larger hippocampi than controls – size correlates with years driving.

Question 10

Relational memory (hippocampus)

Answer 10

Hippocampus plays a role in memory for the new associations – not just spatial ones.

Tested using odor associations in rodents.

Learns preferences in pairs of odors based on the presence of a reward.
A>B, B>C, C>D
Can later infer relationship across pairs
A>C

Lesions to hippocampus disrupt the ability to learn relationship across pairs.

Question 11

Patient K.C.

Answer 11

Patient K.C. had lesion to hippocampus

impaired episodic memory – memory for personal events

Spared semantic memory – can remember and learn facts.

Question 12

Hippocampus in episodic vs semantic memory

Answer 12

Hippocampus plays a role in episodic memory rather than semantic memory.

Episodic memory is related to recognition (reporting details).

Knowing is also related to semantic memory (no details).

Hippocampus activates only for recognition

Question 13

Experimental paradigm from Ranganath et al., 2004

Answer 13

(hippocampus and enncoding)

Studied 360 items presented in different colors during fMRI scanning.

Participants responded by:

Rating whether they had seen the item before (1 new - 6 old)
Reporting the context the item was presented in (color)

fMRI categorized based on responses.
Correct and Incorrect.
Correct Source vs Incorrect Source.

Greater activity in Hippocampus and Parahippocampus for correct compared to incorrect source.

Question 14

Familiarity based encoding

Answer 14

Now look at correlation between BOLD and confidence rating.

A measure of familiarity based recognition.

Found activity in entorhinal cortex.

Not in hippocampus.

Suggests dissociation between hippocampus and entorhinal cortex.

Question 15

Hippocampus and Retrieval

Answer 15

Eldridge et al (2000) measured activity in hippocampus during memory recall.

Measured correct recall as well as remember compared to familiar.

Hippocampus was active only during correct recall and not when items were correct but only familiar.

Suggests supports a role for hippocampus in episodic recollection

Question 16

False memories and context (Cabeza, 2001)

Answer 16

Cabeza, 2001 – had participants listen to related words,

Performed old/new recognition using old – new and false words.

False = same category as old – but not in old list.
Hippocampus did not distinguish between true (actual old words) and false words.

Parahippocampal gyrus was active only for true words.

Hippocampus active in response to the context and relationships of the words

Question 17

Three process theories

Answer 17

Perirhinal cortex involved in memory for objects – input from ventral pathway.

Parahippocampal cortex encodes information relevant to spatial relationships – input from dorsal pathway.

Hippocampus Encodes the item (object) in its context (relationships).

Explains why perirhinal is related to familiarity and hippocampus to recollection. Helps to combine many of the previous theories we already discussed.

Question 18

Sensory / Functional theory

Answer 18

Knowledge is remembered in the same brain sensory and motor areas involved in encoding.

Retrieving memories activates regions of the brain associated with the processing of the specific feature being recalled.
Action words – motor areas
Sound words – auditory areas

Question 19

Cortical storage of memories

Answer 19

Applies even during passive viewing of words
Action words related to the face (Lick) activate the face area of the motor cortex.
Works like “Punch” activate arm area and “Kick” activate leg area.
Suggests that the representation of the meaning of these words is stored in functional regions associated with the semantics.

Question 20

Reactivation of sensory regions in memory

Answer 20

During an encoding stage a word was paired with either an image or sound.

During encoding :

the visual condition activated visual cortex.
The auditory condition activated auditory cortex.

During retrieval only the word was presented and an old/new judgment.

fMRI showed recapitulation during recall in which:

Remembering auditory word reactivation the auditory cortex
Remembering visual words reactivated visual cortex.

Question 21

Two models for abstract knowledge

Answer 21

Distributed only – abstract knowledge emerges from the concrete network

Distributed plus hub – there is a specialized regions for conceptual knowledge

Question 22

Posterior parietal cortex in retrieval

Answer 22

fMRI studies show that dorsal parietal cortex is associated with familiarity and low-confidence.

Ventral regions are more strongly associated with recollection and high confidence recognition.

Interpreted in terms of the attention to memory theory.

Question 23

Dorsal attention stream

Answer 23

top down attention

Memory search and evaluation process.

Question 24

Ventral attention stream

Answer 24

Bottom up attention

Captured by strong memories and retrieval cues

Question 25

Dorsal parietal regions

Answer 25

associated with a positive SME – more active when items are subsequently remembered.

Question 26

Ventral parietal regions

Answer 26

associated with a negative SME – more active when items are subsequently forgotten.

Ventral parietal region associated with failed memory during encoding and successful recollection during retrieval.

Question 27

Synaptic consolidation

Answer 27

Synaptic consolidation involves the synaptic level changes that allow for the persistence of a memory.

Takes minutes to hours

Question 28

System consolidation

Answer 28

System consolidation involves large scale changes in memory circuits

Takes days to years.
Involves changes in the contribution of different brain regions to memory.

Hippocampal lesions

Question 29

Standard theory of consolidation

Answer 29

Standard theory suggests that the memory connections are slowing transferred to the cortical from the hippocampus.

Damage to the hippocampus will not affect such memories but will affect recent memory.

Question 30

Multiple trace theory of consolidation

Answer 30

Multiple trace theory suggest that multiple traces are created in the hippocampus as an episodic memory is recalled and encoded .

Partial disruption of hippocampus can still spare the memory.

Question 31

Sleep and consolidation

Answer 31

Some argue that memory reactivation during sleep is important for consolidation.

Recordings from visual cortex and hippocampus during maze running in an awake animal showed that neurons fired in a specific sequence.

There was also coordination between visual cortex and hippocampus.

The same pattern and coordination was observed during sleep.

Suggests that the events were replayed during SWS.

Question 32

Reversal in parietal lobe activity

Answer 32

Successful memory is associated with decreased activity during encoding and increased activity during recall.

According to attention to memory

Bottom up attention during encoding reflects influence of distraction and other events rather than top down focus on the information to be learned.

Bottom up attention during recall reflects successful capture of attention.

Question 33

outward/inward attention and memory

Answer 33

Alternative have been suggested that include inward vs outward directing of attention.

Ventral parietal regions are related to inward direction of attention related to considering personal aspects of episodic memory.

Effective during retrieval

Ineffective during encoding because encoding requires outward direction of attention.