Memory
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What is Memory?
Memory = the ability of the brain to create, maintain, and retrieve information about the past
Issues of psychological study: Encoding: processing and combining of received information (involves attention) Storage: creation of a record of the encoded information Retrieval/Recall: calling back the stored information in response to some cue for use in some process or activity Issues of neuroscientific study: Connecting function to local brain structures (localization) Contemporary= exposing patterns of activation (holistic processing)
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Early Psychological Studies of Memory
Hermann Ebbinghaus (1885)
1st systematic study of memory
Rehearsed lists of nonsense syllables
ZAT, BOK, QUJ 20 min, 1 hr, 8 hrs, 1 day, 2 day, 6 days, 31 days
Tried to recall after varied intervals
Studied the effect of list length, amount of practice, learning of serially ordered items
Ebbinghaus’s forgetting curve
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Early Psychological Studies of Memory
William James (1890)
Considered conscious experience too transitory to be considered ―Memory‖ Theorized dual memory stores based on introspection method but with little scientific support
very basic precursor to modern memory models Primary Memory:
Immediate memory Never leaves consciousness Gives a faithful rendition of events just perceived Now called Short-Term Memory Permanent memory-- experienced information not readily accessible ―Paths‖ etched into brain tissue—incorrect Now Called Long-Term Memory Copyright © Allyn & Bacon 2005
Secondary Memory:
Early Neurological Studies of Memory
Karl Lashley (1920)
Theorized that physical memory traces called engrams must be made in the brain when learning occurs (no evidence to support at his time but it is coming now!) Lashley removed portions of cortex, varying from 10-50% to study the role cortex played in learning of rats Led to 2 important learning/memory theories Principle of Mass Action: proved that the amount of cortex removed was critical to the learning abilities of the rats= knowledge distributed throughout cortex Equipotentiality: all areas of the cortex are equally important to learning/ no area was proven to be more important than any other area
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Early Neurological Studies of Memory
Donald Hebb (1949)– student of Lashley Theory that changes that occur during learning develop among interconnections of neurons throughout wide areas of the brain Cell Assemblies: loops of neurons become interconnected when learn something - memory is re-activation Some neurological support for this theory
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Neurology of Memory
Memory functions are BOTH located in specialized areas AND distributed throughout the brain
PET scan of person deciding whether a word describes living or non-living object = high activation of frontal cortex (localization) but also activation to a lesser degree in other areas Research shows combination of specialization and generalization applies to many memory operations
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Neurology of Memory
Three main memory sites in the brain-
Cortex:
thinking, problemsolving, remembering
Cerebellum:
motor memory
Hippocampus:
processes new information and routes it to parts of the cortex for permanent storage
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Early Psychological Studies of Memory
Evidence for James’s two memory stores (1890-1960)
Introspection suggests that some things are remembered for a short time, and others for a long time Physiological studies indicate that short term functions can be interrupted, whereas long term functions seem to remain intact
Electroconvulsive shock, head traumas
Psychological experiments suggest two memory stores
Large body of behavioral evidence
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1st Model of Memory
Waugh & Norman (1965)- developed 1st modern behavioral model of memory
Extended James’ early theory
Different than James because they quantified properties of primary memory
Idea of memory as stored in ―boxes-in-the-head‖ Basis of most contemporary models Primary Memory:
Short-Term storage system Independent of secondary memory Has very limited capacity Forgetting due to Decay -- memory fades over time Interference – new information displaces older information Need rehearsal to send information to secondary memory Long-Term storage system
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Secondary Memory:
1st Model of Memory
Model of Primary & Secondary Memory System-- Waugh & Norman (1960s)
Rehearsal
Stimulus
Primary Memory
Secondary Memory
Forgotten
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Expanded Model of Memory
Atkinson & Shiffron Model of Memory (1968)
Also based on early dual store theory But presents a three stage informational processing model
Memory structures fixed– Sensory, Short, Long
Expanded earlier models to include processes of transfer
control processes variable– encoding, storage, retrieval Memory: data being retained Memory Store: structural component that contains the information Copyright © Allyn & Bacon 2005
Make distinction between
Components of Atkinson & Shiffron Model
Sensory Memory Records information from the senses for up to three seconds If information is attended to, transferred to STM otherwise it is lost Short-Term Memory Holds information for up to thirty seconds If the information is rehearsed/attended to, transferred to LTM otherwise it is lost Long-Term Memory Relatively permanent can hold vast amounts of information Interference, decay, brain damage can cause information to be lost
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Classic Information-Processing Model of Memory
Based on Atkinson & Shiffron Model of Memory (1968)
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Sensory Memory
Sensory information held briefly in cortical sensory areas so we can initially process it Also called sensory register or sensory store
Function:
provides continuous flow of updated information available for processing
Types of codes:
Iconic Memory: A fleeting sensory memory for visual images that lasts only for a fraction of a second
Visual Cortex Auditory Cortex
Echoic Memory: A 2 to 3 second sensory memory for Auditory information
Other sensory memories for touch , smell, taste
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Classic Information-Processing Model of Memory
Based on Atkinson & Shiffron Model of Memory (1968)
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Short-Term Memory (STM)
Transitory store of information
Held for 20-30 seconds then either transferred to Long-Term Memory or lost
Intermediate storage area for attended-to environmental stimuli where rehearsal takes place Predominantly auditory Even for non-auditory information So much of STM is reliant on your inner voice — you see the word ―MONEY‖ or ―$‖ and you say ―MONEY‖ in your head. Visual Semantic (meaning based)
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Function:
Types of codes:
Short-Term Memory (STM)
Limited processing capacity
held at most 20 seconds
Based on early work of Peterson & Peterson (1959): •Subjects memorized nonsense syllables, (e.g., MJK, ZRW). •To prevent rehearsal, they were given a distracter task during the waiting period (count backwards by 3 from 506). •When a cue was given, subjects tried to recall the letters. •Short-term memories vanish within twenty seconds.
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Short-Term Memory (STM)
Limited processing capacity
Maintenance Rehearsal: sheer repetition allows information to remain in STM for an indefinite period of time and facilitates transferred to LTM Neurology = STM is a reverberating circuit of neural activity with a self-exciting loop of neurons
Note: Merely holding information in STM does not assure it will not be lost (forgotten)!
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Short-Term Memory (STM)
Limited storage capacity
STM can only hold a limited amount of ―items‖ Miller’s Magic number (1956) = 7 plus or minus 2 Once STM filled– information moved to LTM or lost Benefit of limit = helps us forget what is no longer useful (not cluttered with STM distracting trivia)
Q= WHAT MAKES AN ―ITEM‖?
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Short-Term Memory (STM)
STM storage capacity: Chunking: Process of grouping distinct bits of information into larger wholes to increase short-term memory capacity
What is a chuck varies from person to person depending on their prior experiences # of chunks limited but people can learn to increase the size of chunks– ultimately increasing STM Chunking is one of the executive functions of the prefrontal association cortex
** Chunking makes STM capacity NOT an absolute measure!***
A & B Word List
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Short-Term Memory
Serial Position Curve Indicates the tendency to recall more items from the beginning and end of a list than from the middle. Recency Effect:
The Serial-Position Effect
good recall of words at end of list
Considered to still be in STM ―pushed‖ earlier information out
Primacy Effect:
good recall words at beginning of list
more attention/rehearsal Gets to LTM
Middle words lost!
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From the work of Mary Whiton Calkins, early 1900s
Working Memory
Most widely accepted and used model today!
Baddeley (1986) Re-modeling of STM
Short term memory is woven together with higher cognitive processes-- such as learning, reasoning, and comprehension Focuses on the maintenance of information through the speed of rehearsal
Challenges limited capacity viewed as not a matter of holding 7 +/- 2 items but can keep however much information we can rehearse in a fixed amount of time, so speed of processing is the limiting issue
Transitory area that is more than storage– conceptualized as an active, conscious work space where information is accessible for current use and processing occurs Differs from previous STM models in 2 major ways:
Bring information from Long-Term storage back into intermediate WM for active processing along with incoming information from senses Has 3 (plus 1) components (rather than just single storage bin) Central Executive (master controller) Articulatory Loop/Phonological Store (for verbal) Visiospatial Sketchpad (for visual) New: Episodic Buffer (integrates info so it makes sense)
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Working Memory
•Central Executive: temporary memory about the goals active at the moment, expected inputs during sequences of action, and intermediate products of cognitive activities. Many of the inputs to this system are from cognitive processes rather than perceptual mechanisms. •Phonological Store and Articulatory Loop: a store that is dedicated to spoken information and a sub-vocal rehearsal mechanism. •Visual-Spatial Sketchpad: a separate working memory component used for imagery tasks •Episodic Buffer: an area that binds information from subsidiary systems and Long-term memory into a single representation (so the different parts make sense)
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Psychological Support for Working Memory
Articulatory Loop and word-length effect (Baddeley et al., 1975)
Calculate in your head 37 x 28__ may use visual image may rehearse verbally to retain it use central executive to remember task is multiplication and keep track of where you are
wit, sum, harm, bay, top university, opportunity, aluminum, constitutional, auditorium
Crucial issue is how long it takes to say the word (speed of processing, rather than # of chunks)
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Neuroscientific Support for Working Memory
Many investigators have seen evidence supporting the idea of a central executive
have observed higher cognitive activity in an area in the Dorsolateral Prefrontal Cortex Object WM ―where‖ system spatial location dorsolateral prefrontal cortex ―what‖ system object recognition orbitofrontal prefrontal cortex Phonological Loop Broca’s Area (frontal cortex left hemisphere) responsible for production of speech
Activation of Right Prefrontal Cortex associated with Visuospatial Sketchpad Activation of Left Prefrontal Cortex associated with Phonological Loop
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Support for Working Memory
The Delayed Response Task food placed in well barrier appears animal must remember which well after delay “A not B” Task Jean Piaget modified delayed response task for human children Monkeys with lesions in the frontal cortex and infants under 1 yrs old (immature frontal cortex) cannot perform the task neurons in the Dorsolateral Prefrontal Cortex fire only during the delay portion of the task– as if they are keeping information active
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Classic Information-Processing Model of Memory
Based on Atkinson & Shiffron Model of Memory (1968)
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Long Term Memory
Relatively permanent memory storage Capacity is essentially limitless Permanence is essentially endless
Permastore: very long term storage of information In terms of retrieval, research shows recognition better than recall
must be rehearsed/attended to!
Holds information transferred form STM/WM
Function: hold all information that is not currently being used but that is potentially retrievable
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Long Term Memory
Classes of information stored in LTM (Bower, 1975)
Spatial information
Symbolic structure corresponding to images of our world and where significant objects are located in that cognitive map
Our knowledge of the properties of objects and things Of ourselves, others and how to behave in various social situations
Physical laws
Beliefs
Values and social goals Motor skills
For driving, riding a bike, playing pool, etc. Also problem-solving skills for various aspects of life and our plans for how to achieve various things For understanding language, interpreting art and music, etc.
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Perceptual skills
Long Term Memory
Codes: Auditory
We remember meaning over exact wording
Wanner (1968): LTM is better for changes in wording that results in a change of meaning rather than just a change in word style Memory for meaning is equally good whether people are warned or not
Droodles –Bower et al. (1975)
Visual
Shepard (1967):
LTM capacity is greater for visual information in a picture/scene than for verbal/read information People have better memory for meaning of a picture than meaning of sentences We remember meaning over details (interpretation of the picture rather than the exact picture itself) LTM is better for changes in images that effect the meaning of the picture
Semantic (meaning-based)
Predominant coding used!
Memory for detail is available initially but forgotten rapidly, whereas memory for meaning is retained.
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Neuroscience of LTM Storage
Memory functions are distributed throughout the whole brain-Long-Term memory is stored throughout the Cerebral Cortex!
Possible explanation for infantile amnesia (lack of memories before around age 3-4 yrs) the regions of cortex for long-term storage may not develop fully until later in childhood
Motor memory is stored in the cerebellum
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Transferring information from STM/WM to Long-Term Memory
Memory Consolidation: Process by which chunks of memory re-structured to go into LTM for permanent storage Crucial Brain areas for Memory Consolidation= •Medial Temporal Lobe •Hippocampus •Entorhinal Cortex •Thalamus
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Transferring information from STM/WM to Long-Term Memory
Case of H.M. Damage to temporal lobe and hippocampus inability to transfer explicit memories from short- to longterm memory Hippocampus crucial to consolidation of explicit memories However, he could learn implicit perceptual and motor skills and retain that information over time. Many brain areas crucial to consolidation of implicit memories– but all stored in cerebellum or cortex
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Classification of Long-Term Memories
Neurological and psychological research suggest different types of memory are held in Long-Term Memory
Non Declarative Memory (Implicit)
Procedural Memory
Motor Perceptual Cognitive
Declarative Memory (Explicit)
Episodic Memory
Autobiographical Flashbulb
Semantic Memory
Schemas Scripts
Priming Condition Non-ing Associative
Semantic Repetition Classical Operant
Habituation
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Classification of Long-Term Memories
Declarative Memories: ―Knowing That‖ – stored long-term facts about ourselves and the world
Are Explicit - consciously retrievable memories Crucial for formation = medial temporal lobe structures & thalamus (major sensory relay) 2 types episodic
memory of instances or episodes from events in our lives What did you wear to prom? Memory consolidation = hippocampus memory of facts and general knowledge What is prom? Memory consolidation = entorhinal cortex
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semantic
Classification of Long-Term Memories
Declarative Memories:
Episodic Sub-types- Autobiographical: recollections people have of their own personal experiences and observations (People’s memories are most vivid for times of transition) Flashbulb: Particularly good (vivid) memories for events that are very important or traumatic Semantic Sub-types- Schemas: A mental framework of interrelated concepts in a meaningful organization based of the type of objects that they are, the parts that they tend to have and their typical properties Scripts: A type of schema for a particular event (stereotypic sequences of actions)
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Neuroscience of Long-Term Memories
Declarative Memories and consolidation:
Neuroscience research suggests that memories are stored in the activity and change in neurons (remember Hebb’s Cell Assemblies & Lashley’s Engrams)
Long-Term Potentiation (LTP)
Tendency of nerve cells that have been exposed to a rapidly repeating stimulus to enhance their response tendencies for an extended period of time Belief is that some chemical and/or structural change occurs and the memory is permanently stored Long-Term Declarative memories are believed to begin as the cortex sends information to the hippocampus, a process that strengthens the memory by rapidly and repeatedly exciting the neural circuit in the cortex (New evidence suggests happens during REM sleep!) Copyright © Allyn & Bacon 2005
Classification of Long-Term Memories
Procedural Memories: ―Knowing How‖ – stored longterm knowledge of learned habits and skills
Are implicit - out of awareness Can be motor, perceptual, cognitive or combination examples: riding a bike, driving, tie shoes, reading, mental math) uses many cortical areas depending on type of memory visual priming - visual cortex motor programs - basal ganglia (mid-brain structure important for motor control), cerebellum (motor memory) does not involve temporal lobe and no hippocampus association
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Modern Information Processing Model of Memory
STM/WM
Dorsolateral Prefrontal Cortex Orbitofrontal Prefrontal cortex
LTM
Temporal lobe & Thalamus Visual/Auditory/ Somatosensory Cortex Prefrontal cortex
Hippocampus
Declarative
Entorhinal Cortex
Episodic Buffer
Dorsolateral Prefrontal Cortex
Non Declarative
Many-depends on type
Broca’s Area Temporal Cortex Dorsolateral Prefrontal Cortex
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Factors that effect Retrieval from Long-Term Memory
Practice (Rehearsal) Each time we use a memory, it increases in strength– can reach a higher level of activation so can be retrieved more rapidly Retention is increased through ―overlearning‖ Power Law of Learning= linear relationship repeated research shows: the more practice, the faster the recall but with diminishing returns Research shows LTM is better when practice is spread over a long period of time – distributed vs. mass (called the Spacing Effect)
new rat evidence relates hippocampal re-activation during REM and learning (suggests more REM more activation of hippocampal more consolidation into LTM better learning)
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Factors that effect Retrieval from Long-Term Memory
Depth of Processing (Craik & Lockhart, 1972)
Theory that states that rehearsal improves memory only if the material is rehearsed (practiced) in a deep and meaningful way– attended to, fully analyzed, enriched by associations or images PROCESSING IS THE KEY TO STORAGE! Deeper processing in terms of meaning (semantics) leads to better memory than shallow processing looking only at surface form. Emphasizes semantics as a primary code/organization of information in LTM
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Factors that effect Retrieval from Long-Term Memory
Depth of Processing is supported by research!
Subjects were shown lists of words and asked to use one of three strategies:
Visual: Is the word printed in capital letters? Acoustic: Does the word rhyme with _____? Semantic: Does the word fit the sentence _________?
The more thought involved (deeper processing through semantic rehearsal), the better was their memory.
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Factors that effect Retrieval from Long-Term Memory
Elaborative Processing
Embellishing an item to be remembered with additional information improves recall Elaborative processing results in better memory even if the processing is not focused on the meaning of the material The Generation Effect-- Having the person elaborate on the information themselves yields better memory than just presenting the information to them (taps into self-schema/ narcissistic trait rich and extensive network available for storing self-information) The Self-Reference Effect– People tend to recall more information that refers to themselves than about other information
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Factors that effect Retrieval from Long-Term Memory
Context
Encoding Specificity Principle: any stimulus encoded along with an experience can trigger one’s memory of the experience Context-Dependent Learning: easier to retrieve information from memory when in the same situation as when the information was first encoded (environment) State-Dependent Learning: easier to recall information if state of mind is the same as when the information was first encoded (mood)
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Factors that effect Retrieval from Long-Term Memory
Incidental vs. Intentional Learning
Repeated research shows:
Whether a person intends to learn/later recall does not matter! What matters is how the person processes the information at its presentation People do tend to remember more when they intend to learn because they tend to engage in other activities
Rehearsal Elaborative processing
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Factors that effect Retrieval from Long-Term Memory
Memory is Constructive!
Not simply a matter of consuming facts about the world and regurgitating them: Prior experience, post-event information, perceptual factors and desire to recall certain events over others effect LTM Research shows people have tendencies to distort memory: Eye Witness testimony is susceptible to suggestion Misattribution: recall of what we think we should have seen, rather than what we actually saw
Eye Witness Transference (mis-perception of an event where witness replaces one person with another in memory) Bias in recall
Tend to distort episodic memories more than semantic memories
we use more of our semantic memories in real-life situations--refresh your semantic memory (strengthen memory trace through activation) plus most semantic memories fit into pattern & corrected by others
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Long-Term Memory
Forgetting
WHY???
Lack of Encoding Decay Interference Repression
Information not stored in LTM
Memory may exist but difficult (impossible) to retrieve
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Long-Term Memory
Forgetting
Can You Recognize a Penny?
One reason
people forget is due to lack of encoding.
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Long-Term Memory
Forgetting
Decay Theory:
Memory traces simply weaken in strength over time Some neurological evidence to explain decay– Long-Term Depression (LTD) = decrease in neural responsiveness
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Long-Term Memory
Forgetting
Interference: Learning additional associations to a stimulus can cause old ones to be forgotten (lost)
Proactive Interference
The tendency for previously learned material to disrupt the recall of new information Swimmer has problem learning new stroke because close to well-known stroke The tendency for new information to disrupt the memory of previously learned material Difficulty skiing because recently learned to snowboard
Retroactive Interference
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Long-Term Memory
Forgetting
Repression:
Freud says that when we have memories, impulses, desires, and thoughts that are too difficult or unacceptable to deal with, we unconsciously exclude them from our consciousness (some people like to say we "push" them down from our consciousness to our unconsciousness). Not universally accepted (because of issues of suggestibility)
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Amnesic Effects of Brain Damage
Amnesia:
Temporary or permanent loss of memory
depending on location of brain damage, could be an issue of
Anterograde Amnesia– can’t form new LTM
(ex. Hippocampus damage) or
Retrograde Amnesia– can’t remember past events (damage to cortex where stored or area needed for retrieval (such as thalamus, cerebellum, etc.)
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Amnesic Effects of Brain Damage
Amnesia due to temporal lobe damage
case of H. M. - bilateral removal of medial temporal lobes (including hippocampus) to control for epilepsy inability to transfer declarative memories from short- to long-term memory
Amnesia due to thalamic damage
case of N. A. - fencing accident damaged left part of thalamus inability to learn new verbal material - can learn faces and locations
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Amnesic Effects of Brain Damage
Amnesia due to Korsakoff’s Syndrome
disease of chronic alcoholics related to loss of vitamin B1 suffer both anterograde amnesia (can’t form new memories) and retrograde amnesia (amnesia for past events) persevere in useless strategy that worked before show no improved learning when released from proactive inhibition (old memories interfere with recall of new) damage to thalamus, cerebellum, cerebral cortex (frontal lobes)
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Amnesic Effects of Brain Damage
Amnesia due to Electroconvulsive Treatment (ECT)
shock used to treat severe depression causes loss of memory, particularly for recent events (LTM intact) ECT induces seizures in temporal lobe - probably disrupts hippocampus
thalamic damage (N.A.; Korsakoff’s) leads to normal rates of forgetting hippocampal and amygdala damage (H.M.; ECT) leads to rapid rates of forgetting
Differences in rates of forgetting
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