26.2 - Human Memory

Question 1

Summarise the main types and subtypes of memory/learning.

Answer 1

• Declarative (explicit) -> Conscious memory of facts and events
  
  • Semantic -> Factual information (e.g. location of Eiffel tower)
  • Episodic -> Personal experiences (e.g. what you had for breakfast)
• Non-declarative (implicit) -> Modes of learning that are non-conscious
  
  • Skills/Procedural -> Learning skills and habits (e.g. how to ride a bike)
  • Category -> Assigning objects/skills in the world into classes for the purpose of generalization, discrimination, and inference (e.g. movie genres)
  • Priming -> Where identification of a stimulus is improved by an earlier encounter of that or other stimuli (e.g. being able to complete a partially completed letter once you recognise what it is)
  • Associative -> Learning to associate one stimulus with another stimulus (i.e. conditioning).
  • Non-associative -> When repeated exposure to a stimulus leads to a change in how intensely it is perceived (e.g. repeatedly hearing a sound in the background may cause you to tune it out).

Question 2

Compare whether semantic or episodic (both declarative) memories are stored in the long term.

Answer 2

• Semantic memories (i.e. facts) are likely to be stored in long-term memory
• Episodic memories (i.e. experiences) are unlikely to be stored in long-term memory, as the name suggests

Question 3

What is short-term memory?

[IMPORTANT]

Answer 3

• The process of holding memories for between 3 and 18 seconds, such as the digits of a phone number. It very rapidly decays.
• Note that this is different from the colloquial definition of short-term memory.

Question 4

Give some experimental evidence for how short-term memory can be assessed.

[EXTRA]

Answer 4

• Verbal short-term memory is assessed using a digit span test (seeing how many digits the individual can remember)
• Visuospatial short-term memory is assessed using the Corsi blocks test (tapping the blocks in the correct sequence)

Question 5

Where in the brain are verbal and visuospatial short-term memory stored? Give some experimental evidence for this.

Answer 5

• Verbal STM = Left parietal lobe
  
  • Patient KF (Shallice & Warrington, 1970) with a left parietal lesion had a digit span of only 2 but normal spatial span on Corsi blocks and normal long-term memory
• Visuospatial STM = Right hemisphere
  
  • Patient ELD (Hanley et al, 1991) with a right hemisphere lesion had an impaired spatial span but normal digit span and long-term memory

Question 6

What is working memory?

[IMPORTANT]

Answer 6

• A cognitive system with a limited capacity that can hold information temporarily.
• Working memory is important for reasoning and the guidance of decision-making and behavior.

Question 7

Describe a model of working memory.

Answer 7

(Baddeley, 2003):

• There are ‘slave’ storage systems for visuospatial and verbal short-term memory -> These have little function, except to store information
• The information stored there can be used and manipulated by executive control -> e.g. Putting into context the start of a sentence once you have heard the full sentence
• The information can also be stored in long-term memory, which is beyond working memory

Question 8

Describe the areas of the brain involved in working memory.

Answer 8

One theory suggests:

• Parietal cortex -> This is where short-term memory is stored
• Prefrontal cortex -> This is where manipulation and monitoring of information occurs

Question 9

How does memory change with age?

Answer 9

• Short-term memory improves during development
• But both short-term and long-term memory decline with age
• The only exception to this is semantic memory (e.g. facts about the world), which accumulates with time

(Reuter-Lorenz, 2009)

Question 10

Is working memory related to intelligence? Give some experimental evidence.

Answer 10

(Colom, 2008):

• Found that working memory and intelligence were highly correlated

(Jaeggi, 2008):

• Tested whether training working memory can lead to improvements in fluid intelligence
• Found that improving working memory did significantly increase performance on a non-verbal intelligence test
• However, not all other studies have been able to replicate this finding and it remains controversial

Question 11

Where is episodic long-term memory stored in the brain?

Answer 11

The hippocampus is involved in consolidating the memories, which are ultimately largely stored in the cerebral cortex (i.e. they pass from the hippocampus to the cortex).

Question 12

Compare the regions of the brain involved in short and long-term memory.

Answer 12

• Short term = Parietal cortex (and prefrontal cortex in working memory)
• Long term = Hippocampus (medial temporal lobe) and cerebral cortex

Question 13

Describe the case of patient HM and what this tell us about long-term memory.

[EXTRA]

Answer 13

• Patient H.M. suffered from epilepsy and had his hippocampus and parahippocampal regions removed as a possible treatment
• The result of this was that he developed severe anterograde amnesia, meaning that he was unable to form new memories
• He also had graded retrograde amnesia, meaning that his long-term past memory was more affected most regarding memories just before the operation -> He was able to recall childhood memories but struggled with memories of the years before the operation
• This demonstrated the importance of the hippocampus in forming episodic long-term memories

Question 14

How can patient HM’s graded retrograde amnesia be explained?

Answer 14

• Memory consolidation is thought to work by initially sotring the memories in the hippocampo-cortical regions
• It is then eventually transferred fully to the cortex
• This explains why patient HM’s loss of the hippocampus caused him to not only develop anterograde amnesia, but also lose some recent past memories that had not yet been fully consolidated

Question 15

What is Ribot’s law?

[IMPORTANT]

Answer 15

• The idea that new memories are more likely to be lost than old memories.
• This can be explained by the theory of memory consolidation, where memories are initially stored in the hippocampo-cortical regions and then eventually transferred fully to the cortex -> Once it is fully consolidated, it is less likely to be lost

Question 16

What are the causes and symptoms of Korsakoff syndrome?

[IMPORTANT]

Answer 16

• It is a syndrome characterised by severe memory loss and confabulation
• It is caused by thiamine (vit. B1) deficiency, which is often seen in alcoholics
• The mammillary bodies in the Papez circuit seem to be particularly affected
• It is reversible

Question 17

Give some experimental evidence for the “last in, first out” theory of memory.

[EXTRA]

Answer 17

(Butters & Cermak, 1986):

• Studied a professor who developed Korsakoff’s syndrome shortly after writing his autobiography
• Assessment showed that the professor retained far better memory of events that were a long time ago, compared to just before his diagnosis

Question 18

What is procedural memory?

Answer 18

A form of implicit memory relating to how to perform different actions and skills (e.g. riding a bike).

Question 19

What is priming?

Answer 19

Where identification of a stimulus is improved by an earlier encounter of that or other stimuli (e.g. being able to complete a partially completed letter once you recognise what it is).

Question 20

Amensics typically have lesions of…

Answer 20

Medial temporal lobe (e.g. hippocampus)

Question 21

Are procedural memory and priming affected in patients with hippocampal lesions (i.e. amnesics)?

Answer 21

No, they appear to be intact:

• Patient HM was able to learn in a mirror tracing task (procedural learning).
• Dr Claparède pricked an amnesic woman in the hand with a pin every time he shook her hand. Even though she couldn’t remember him each time she saw him, she became aversive to shaking his hand (priming).

Question 22

Give an example of a condition with medial temporal lesions that leads to amnesia.

Answer 22

Alzheimer’s disease (it tends to affect the entorhinal cortex and then the hippocampus)

Question 23

Describe the concepts of primancy and recency.

[IMPORTANT]

Answer 23

• When information is presented in a list, we tend to remember the most from the start of the list (primancy) and end of the list (recency).
• Clinical relevance: Patients recall best the information you give them at the beginning and end of the consultation.

Question 24

How can recency be lost? What is this evidence for?

Answer 24

• The recency effect is lost when there is gap between the end of the information and recall that is filled with an activity, such as counting back in 3s.
• Counting backwards prevents rehearsal and retention of words in short-term memory. Thus, this demonstrates that recency is likely to be mediated by STM.

Question 25

Are recency and primacy affected in medial temporal lobe lesions (e.g. hippocampus)?

Answer 25

• Recency is not affected, because it is mediated by short-term memory, which is not controlled by the medial temporal lobe
• Primacy is affected, because it is mediated by long-term memory, which is controlled by the medial temporal lobe

Question 26

Memory is…

Answer 26

Reconstructive

Question 27

What is meant by memory being reconstructive?

Answer 27

We do not store and recollect memories exactly as they are, but much rather we reconstruct memories based off information and previous knowledge.

Question 28

Give some experimental evidence for memories being modified or even created.

[EXTRA]

Answer 28

(Loftus, 1974):

• Participants watched a video of a car crash
• They were then asked to judge the speed at which the cars crashed
• The average speed the participants estimated varied depending on the verb that was used
• Some also falsely recalled seeing broken glass

(Wells, 1998):

• Studied eyewitness testimony
• Participants watched an 8 second security video and asked to pick the gunman from photographs.
• Every observer picked someone despite the fact that none of the people in the photos was the gunman.

Question 29

What is confabulation?

[EXTRA]

Answer 29

• False memories without conscious knowledge of their falsehood.
• These are often plausible, but imaginary, recollections of an event or sometimes a grand account of personal life.
• They occur after orbitofrontal cortex damage and in Korsakoff’s syndrome, perhaps as a consequence of failures in control over memory retrieval.

Question 30

Compare how and where episodic and semantic long-term memories are stored.

Answer 30

• Episodic memory is first stored in the hippocampus (medial temporal lobe) and then consolidated in the cortex.
• Semantic memory is eventually found to be stored in the left temporal pole. It is quite likely that the hippocampus plays a role in the formation of these memories, but there is more uncertainty about this.