Neuropsychology: The Remembering Brain Flashcards
What is memory?
-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
What is the case of H.M.?
-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
What is the taxonomy of memory?
-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
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What is the taxonomy of short-term memory?
-Phonological short-term memory
-Visuo-spatial short-term memory
-Working memory
What are characteristics of the phonological short-term memory?
-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.)
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What are characteristics of the visuo-spatial short-term memory?
-Luck & Vogel (1997): brief displays of arrays of oriented coloured lines: suggests capacity limitation of ~4 objects
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-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
What brain areas are involved in the visuo-spatial short-term memory?
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
What are characteristics of the working memory?
-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
What is Baddeley’s model of working memory?
-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
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Which modality-specific buffers for temporary storage are there in Baddeley’s model of working memory?
-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)
How are the working memory and prefrontal cortex related?
-PFC involved in working memory
-Petrides’ theory of working memory
What is Petrides’ theory of working memory?
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)
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What is the taxonomy of long-term memory?
-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
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What are characteristics of the declarative memory?
-Part of long-term memory
-Explicit memory
-Info that can be consciously accessed
-Can be divided into episodic and semantic memory
What is the episodic memory?
-Part of long-term, declarative memory
-Events
-Specific personal experiences form particular time and place
What is the semantic memory?
-Part of long-term, declarative memory
-Facts
-World knowledge, object knowledge, language knowledge, conceptual priming
What are characteristics of the non-declarative memory?
-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
What is the procedural memory?
-Part of long-term, non-declarative memory
-Skills: motor and cognitive
What is the perceptual representation system?
-Part of long-term, non-declarative memory
-Perceptual priming
What is classic conditioning?
-Part of long-term, non-declarative memory
-Conditioned responses between 2 stimuli
What is non-associative learning?
-Part of long-term, non-declarative memory
-Habituation and sensitization
What is amnesia?
-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
What different types of amnesia are there?
-Anterograde: difficulties in acquiring new memories after brain injury
-Retrograde: difficulties in remembering events from before brain injury
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What different kinds of brain injury can cause amnesia?
-Neurosurgery
-Strokes
-Head injury
-Viruses
-Alzheimer’s disease (as symptom)
What is the neural basis for amnesia?
-Frontal lobe
-Fornix
-Thalamus
-Hippocampus
-Mammillary body
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Which types of memories are affected in amnesia?
Episodic memory
Which types of memories are less affected in amnesia?
-Short-term memory
-Non-declarative (procedural) memory
-Semantic memory
How does the episodic memory work in amnesia?
-Impaired
-Core symptom in amnesic patients
How does the short-term memory work in amnesia?
-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
How does the non-declarative, procedural memory work in amnesia?
-Spared
-Can learn new skills (ex: mirror drawing)
-Task has to be explained every time, but performances improve
How does the rest of the non-declarative memory work in amnesia?
-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
How does the semantic memory work in amnesia?
-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)
What is Ribot’s law?
-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
What different theories are there to explain the function of the hippocampus and medial temporal lobes in long-term memory?
-Consolidation theory
-Multiple-trace theory
-Cognitive map theory
What is the consolidation theory about the role of the hippocampus and medial temporal lobes in memory?
-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
What is the multiple-trace theory about the role of the hippocampus and medial temporal lobes in memory?
-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
What is the cognitive map theory about the role of the hippocampus and medial temporal lobes in long-term memory?
-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: /
Which mechanisms are there in memory?
-Recall
-Cued recall: needs recollection
-Recognition: can be solved with familiarity (knowing) or recollection
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Which brain regions are important for the different mechanisms of memory?
-Perirhinal cortex: item representation
–>Important for familiarity
-Parahippocampal cortex: context representation
-Entorhinal cortex
-Hippocampus: items in context
–>Important for recollection
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Which different roles do the prefrontal lobes have in memory?
-Working (with) memory
-Memory encoding
-Monitoring memory retrieval
-Evaluating retrieved memories
-Lesion: confabulation
What is the role of the prefrontal cortex in working (with) memory?
-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
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What is the role of the prefrontal cortex in memory encoding?
-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
What is the role of the prefrontal cortex in monitoring memory retrieval?
-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)
What is the role of the prefrontal cortex in evaluating retrieved memories?
-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
What are confabulations?
-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
