Neuropsychology: The Remembering Brain

Question 1

What is memory?

Answer 1

-Ability to learn from and recall experiences
–>Helps in predicting future situations and flexibly adapt behavior and thoughts to new situations
-Related to plasticity: brain’s ability to change at neural level as result of experience
–>Persists throughout life (although greatest in childhood)
-Learning and memory: brain-level properties, not specialized faculties
-Different regions of brain contribute to learning and memory in different ways
–>Some regions specialized for words, others for perceptual learning, others for remembering episodes from one’s life
-Different types of memory can be selectively affected by brain damage

Question 2

What is the case of H.M.?

Answer 2

-Epileptic seizures at age 10
-Surgical resection of bilateral medial temporal lobes (including hippocampus) at age 27: resulted in profound amnesia
-1 of most cited articles in cognitive neurosciences

Question 3

What is the taxonomy of memory?

Answer 3

-Environmental input
-Sensory memory: visual, auditory and tactile
-Short-term memory: limited capacity memory for info currently “in mind” and further manipulation (working memory)
-Long-term memory: stored info that need not be currently accessed or consciously accessible
(image)

Question 4

What is the taxonomy of short-term memory?

Answer 4

-Phonological short-term memory
-Visuo-spatial short-term memory
-Working memory

Question 5

What are characteristics of the phonological short-term memory?

Answer 5

-Capacity limit of phonological short-term memory assessed by span tasks
–>Miller (1956) suggests span is 7 +/- 2 meaningful “chunks”
–>Others: limit lower, chunking relies on long-term memory
–>Limit may be lower if info is not rehearsed (ex: articulatory suppression through mouthing irrelevant speech)
-Capacity not strictly related to meaningfulness of chunks
–>Span length lower for polysyllabic words (skeleton, binoculars, etc.)
–>Span length lower for phonologically similar words (map, cat, cap, etc.)
(image)

Question 6

What are characteristics of the visuo-spatial short-term memory?

Answer 6

-Luck & Vogel (1997): brief displays of arrays of oriented coloured lines: suggests capacity limitation of ~4 objects
(image)
-Ranganath et al. (2004): maintaining single object in short-term memory involves activating ventral stream representations
-Likely source of activation: parietal areas (ex: selected & sustained attention) and prefrontal cortex (ex: task-setting)
–>Intraparietal sulcus activity related to intra- and interindividual differences in capacity

Question 7

What brain areas are involved in the visuo-spatial short-term memory?

Answer 7

Fusiform face area: FFA, for faces
-Parahippocampal place area: PPA, for houses
-Superior temporal cortex: content of memory
-Occipital-temporal cortex: content of memory
-Sensory regions: content of memory
-Parietal cortex: selected and sustained attention

Question 8

What are characteristics of the working memory?

Answer 8

-Info passively retained in limited capacity short-term stores (ex: phonological or visuo-spatial short-term memory)
–>Lie posterior (parietal lobes), with content of info also in sensory regions (Ranganath study)
-Prefrontal cortex responsible for refreshing info in stores (rehearsal) and manipulating that info (ex: using list of numbers in short-term memory to perform calculations)
–>Ex: central executive in Baddeley and Hitch

Question 9

What is Baddeley’s model of working memory?

Answer 9

-Working memory as work space in which info processed and results temporarily stored
-Central executive: controls what happens in and interacts with buffers
-Short-term systems: modality-specific buffers for temporary storage
-Each buffer has limited capacity
-Direct or indirect interaction with long-term memory
(image)

Question 10

Which modality-specific buffers for temporary storage are there in Baddeley’s model of working memory?

Answer 10

-Visuo-spatial sketchpad: storing visual info (ex: visual semantics)
-Episodic buffer: storing aspects of events and multidimensional aspects (ex: episode long-term memory)
-Phonological loop: storing auditory info through constant repetition (ex: language)

Question 11

How are the working memory and prefrontal cortex related?

Answer 11

-PFC involved in working memory
-Petrides’ theory of working memory

Question 12

What is Petrides’ theory of working memory?

Answer 12

In humans: division of PFC into at least 2 separate processes
-Ventrolateral prefrontal cortex: activating, retrieving and maintaining info held in posterior cortex (frontal)
–>Posterior cortex: storage side of info (non-frontal)
-Dorsolateral prefrontal cortex: manipulating and monitoring info in mind (frontal)
(image)

Question 13

What is the taxonomy of long-term memory?

Answer 13

-Declarative memory: explicit memory
–>Episodic memory: events
–>Semantic memory: facts
-Non-declarative memory: implicit memory
–>Procedural memory
–>Perceptual representation system
–>Classical conditioning
–>Non-associative learning
(image)

Question 14

What are characteristics of the declarative memory?

Answer 14

-Part of long-term memory
-Explicit memory
-Info that can be consciously accessed
-Can be divided into episodic and semantic memory

Question 15

What is the episodic memory?

Answer 15

-Part of long-term, declarative memory
-Events
-Specific personal experiences form particular time and place

Question 16

What is the semantic memory?

Answer 16

-Part of long-term, declarative memory
-Facts
-World knowledge, object knowledge, language knowledge, conceptual priming

Question 17

What are characteristics of the non-declarative memory?

Answer 17

-Part of long-term memory
-Implicit memory
-Info not consciously accessible
-Can be divided into procedural memory, perceptual representation system, classical conditioning and non-associative learning

Question 18

What is the procedural memory?

Answer 18

-Part of long-term, non-declarative memory
-Skills: motor and cognitive

Question 19

What is the perceptual representation system?

Answer 19

-Part of long-term, non-declarative memory
-Perceptual priming

Question 20

What is classic conditioning?

Answer 20

-Part of long-term, non-declarative memory
-Conditioned responses between 2 stimuli

Question 21

What is non-associative learning?

Answer 21

-Part of long-term, non-declarative memory
-Habituation and sensitization

Question 22

What is amnesia?

Answer 22

-Memory disorder in which there is loss of memory that occurs after brain damage
–>Different types
-Can arise from different brain injuries
-Neural basis: different brain regions associated with amnesia
-Preserved and impaired memory in amnesia

Question 23

What different types of amnesia are there?

Answer 23

-Anterograde: difficulties in acquiring new memories after brain injury
-Retrograde: difficulties in remembering events from before brain injury
(image)

Question 24

What different kinds of brain injury can cause amnesia?

Answer 24

-Neurosurgery
-Strokes
-Head injury
-Viruses
-Alzheimer’s disease (as symptom)

Question 25

What is the neural basis for amnesia?

Answer 25

-Frontal lobe
-Fornix
-Thalamus
-Hippocampus
-Mammillary body
(image)

Question 26

Which types of memories are affected in amnesia?

Answer 26

Episodic memory

Question 27

Which types of memories are less affected in amnesia?

Answer 27

-Short-term memory
-Non-declarative (procedural) memory
-Semantic memory

Question 28

How does the episodic memory work in amnesia?

Answer 28

-Impaired
-Core symptom in amnesic patients

Question 29

How does the short-term memory work in amnesia?

Answer 29

-Less impaired
-Normal digit span (Baddeley & Warrington, 1970)
-Can remember and produce number for 15mins by continuously repeating (Milner, 1971)
–>But forgot withing 1min of stopping and no recollection of attempting

Question 30

How does the non-declarative, procedural memory work in amnesia?

Answer 30

-Spared
-Can learn new skills (ex: mirror drawing)
-Task has to be explained every time, but performances improve

Question 31

How does the rest of the non-declarative memory work in amnesia?

Answer 31

-Spared
-Amnesic patients can learn rules of weather prediction game, but can’t remember which cards previously seen
-Patients with Parkinson’s disease: opposite pattern (remember seen cards, can’t learn rules)
-Show priming in stem completion, despite inability to recollect word
-Improve on Gollin Incomplete Figures test, despite inability to recollect having done task before

Question 32

How does the semantic memory work in amnesia?

Answer 32

-Generally intact semantic memory
–>But not sure if this reflects fact that most semantic knowledge acquired early in life
-Generally better memory for early life (Ribot’s law)
-Some patients: able to learn new semantic knowledge, but at which rate and with which mechanisms debatable (ex: lot of repetition helps, so maybe spared cortex involved)

Question 33

What is Ribot’s law?

Answer 33

-Consolidation: process by which moment-to-moment changes in brain activity translated into permanent structural changes
-Involvement of hippocampus and medial temporal lobes
-Older events/memories: more consolidated and less dependent on hippocampus
-Can explain amnesia: memories not fully consolidated lost with brain damage to hippocampus and medial temporal lobes

Question 34

What different theories are there to explain the function of the hippocampus and medial temporal lobes in long-term memory?

Answer 34

-Consolidation theory
-Multiple-trace theory
-Cognitive map theory

Question 35

What is the consolidation theory about the role of the hippocampus and medial temporal lobes in memory?

Answer 35

-Type of info: episodic and semantic memories
-Duration of storage: temporary (years in humans)
-Relationship to cortically based memories: memories transferred from hippocampus to medial temporal lobes
-Explanation of amnesia: old memories not stored in hippocampus, so spared by damage

Question 36

What is the multiple-trace theory about the role of the hippocampus and medial temporal lobes in memory?

Answer 36

-Type of info: contextualized memories
-Duration of storage: permanent
-Relationship to cortically based memories: memories in medial temporal lobes more schematic (lack content) and more semantic-like
-Old memories less rich context and so spared by damage

Question 37

What is the cognitive map theory about the role of the hippocampus and medial temporal lobes in long-term memory?

Answer 37

-Type of info: spatial memories
-Duration of storage: permanent
-Relationship to cortically based memories: hippocampus stores spatial info whereas medial temporal lobes store other kinds of info
-Explanation of amnesia: /

Question 38

Which mechanisms are there in memory?

Answer 38

-Recall
-Cued recall: needs recollection
-Recognition: can be solved with familiarity (knowing) or recollection
(image)

Question 39

Which brain regions are important for the different mechanisms of memory?

Answer 39

-Perirhinal cortex: item representation
–>Important for familiarity
-Parahippocampal cortex: context representation
-Entorhinal cortex
-Hippocampus: items in context
–>Important for recollection
(image)

Question 40

Which different roles do the prefrontal lobes have in memory?

Answer 40

-Working (with) memory
-Memory encoding
-Monitoring memory retrieval
-Evaluating retrieved memories
-Lesion: confabulation

Question 41

What is the role of the prefrontal cortex in working (with) memory?

Answer 41

-Involved in online maintenance and manipulating info (includes working memory and working with memory)
-Lesions: often have disorganized memory (not lost, but can’t work with memory anymore)
-Similar role in long-term as in working memory
-Distinction between ventrolateral prefrontal cortex and dorsolateral prefrontal cortex
-Evidence in humans for different functional specialization of right and left hemisphere
(image)

Question 42

What is the role of the prefrontal cortex in memory encoding?

Answer 42

-Associated with ventrolateral prefrontal cortex and dorsolateral prefrontal cortex
-Functional imaging: ventrolateral prefrontal cortex
–>Higher activity for deep encoding (ex: semantic) than shallow (ex: orthographic) encoding
–>Higher activity in left ventrolateral prefrontal cortex for verbal encoding
–>Higher activity in right ventrolateral prefrontal cortex for non-verbal stimuli

Question 43

What is the role of the prefrontal cortex in monitoring memory retrieval?

Answer 43

-Dorsolateral prefrontal cortex (particularly right) activated more when:
–>Retrieval cues are minimal (ex: free recall > cued recall)
–>Context needs to be retrieved rather than yes/no recognition
-May relate to wider role in monitoring whether currently held info (in this instance: retrieved from long-term memory) is relevant to goals of task, as also found in comparable working-memory tasks (ex: N-back)

Question 44

What is the role of the prefrontal cortex in evaluating retrieved memories?

Answer 44

-Source monitoring: process by which retrieved memories are attributed to original context (ex: seen vs imagined, told vs read, intended vs enacted)
–>Important for context of memory: remembering when learning about memory and from which source
-Qualitative characteristics of retrieved memories used for source monitoring (ex: event more likely to be seen than imagined if perceptual details are recalled)
–>Prefrontal cortex damage: poor source memory, despite good recognition memory
–>Cannot be solved through familiarity

Question 45

What are confabulations?

Answer 45

-False and sometimes self-contradictory memories that patients believe to be real (without intention of lying)
-Different explanations: failure to retrieve info, failure of source monitoring or failure to suppress irrelevant info
-Associated with damage to different regions than in classical amnesia: orbitofrontal cortex