NSCI 410 Lecture Notes - Lecture 17: Visual Cortex, Episodic Memory, Memory Consolidation

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Short-Term or Working Memory
Encoding of Information: Interaction with Long-Term Memory
information can enter st memory from sensory of lt memory
working memory – memory for new information and information retrieved
from long-term memory; same as st memory
represents behaviour that takes place inside our head – represents our
ability to remember what we have just perceived and to think about it in
terms of what we already know
Primacy and Recency Effects
free-recall task – remember what you can of information that was just given to
you
primacy effect – tendency to remember initial information due to opportunity
for rehearsal which causes them to be stored in lt memory
recency effect – tendency to remember later information due to fact that
they are last to be rehearsed so are still in st memory
pointed out by Atkinson and Shiffrin
Limits of Working Memory
Llyod and Margaret Petersonpresented people with stimuli composed of
3 consonants: JRG
people recalled info 30 seconds later
when made to count backwards from 3-4 digit numbers consonants were
only accesible for a few seconds and dropped to zero after 15-18 seconds
stimuli remain in st memory for 20 seconds unless rehearsed
Miller – the magical number 7 plus or minu 2: people can retain on average
7+or- 2 pieces of information
chunking – process by which information is simplified by rules, which make
it easily remembered once rules are learned
can remember more if information can be organized into more meaningful
sequence
McNamara and Scott – taught people to chain unrelated words together as
they listened to them – imagined story involving those words
Varieties of Working Memory
Phonological Working Memory:
phonological short-term memoryshort term memory for verbal
information (whether presented visually or accoustically)
Conrad – showed how quickly visually presented information becomes
encoded acoustically
briefly showed people lists of 6 letters and then asked them to write letters
saw letters visually but when made errors, they were accoustical (V vs. B)
shows that words were encoded acoustically
phonological memory may be produced by activity in auditory system by
circuits of neurons in auditory association cortex
subvocal articulation – unvoiced speech utterance
although no actual movement may occur, is possible activity occurs in neural
circuits that control speech
when we invision something in our minds It is caused by activity in neurons in
visual association cortex
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voice in head is probably from activity of neurons in motor association cortex
Conrad – attempted to determine whether subvocal articulation played role in
phonological working memory
study on deaf children (could not confuse letters because of their sounds)
children who made accoustical errors were ones who were rated as best
speakers by teachers
deaf children who could speak best encoded letters in terms of movements
they would make to pronounce them
clear evidence for articulatory code in working memory
people may use acoustical and articulatory coding – simulatenously say word
and feel themselves say it in head
phonological code stored in lt memory also might help to strengthen rehearsed
information
conduction aphasia is best evidence for existence of phonoligcal st memory
conduction aphasia – inability to remember words that are heard, although
they usually can be understood and responded to appropriately; caused by
damage to the connection between Wernicke's and Broca's - deficit in
phonological working memory; might disrupt acoustical st memory by making
such subvocal verbal rehearsal difficult or impossible
Visual Working Memory:
possess working memory that contains visual information either obtained from
immediate environment by means of sense organs or retrieved from lt memory
does not encode all details – find prototype in lt memory
DeGroot – showed chessboards to expert players and to novices and if
position of pieces represented game in progress, experts could glance at board
for a few seconds and then look away and report position of each piece but
novices could not; experts could also recognize immediately if positions were
placed haphazardly
st memories for positions depended on organizational rules stored in lt
memory as result of years of chess playing
Gzowski – found similar pattern in Gretzsky's hockey playing
have ability to manipulate visual information in working memory
Shepard and Metzler – presented people with pairs of drawings that could be
perceived as 3D constructions of cubes and found people could accurately
judge if pairs were same shape even if rotated; were able to do so in head and
ones that were more rotated, took longer to judge
Loss of Information from ST Memory:
st memory information controls behaviour and changes lt memory
can decay but rehearsal refreshes it – but mostly due to displacement
Waugh and Norman – heard lists of 16 digits where last digit was
accompanied by tone and called probe digit – when people heard it they had to
think back to last occurence of same digit that tell which digit followed that
one; distance between target and probe was 1-12 items
critical variable was number of items, not time that elapsed – shows that
new information displaces old information in st memory
also showed decayed if slow and a lot of digits were in between – but less of
an effect
St memory is encoded according to previously learned rules and information in
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LT memory determines nature of encoding
Learnend Encoding in Long Term Memory
perceptual memories involve alterations in circuits of neurons in sensory
association cortex of brain, visual memories in visual association cortex,
auditory in auditory association cortex, motor memories in motor association
cortex in frontal lobes
memories that involve combinations of perceptual information involve
establishment of different connections between different regions of association
cortex
learning to perform particular behaviour involves establishing connections
between appropriate regions of sensory and motor cortexes
memory – inovles active and passive processes
The Consolidation Hypothesis
traditional view of memory is that it consists of 2 stage process: consolidation
consolidation – process by which information in st memory is transferred to lt
memory, presumably because of physical changes that occur in neurons in
brain
st memory consists of activity of neurons that encodes information received
from sense organs and once acitibity subsides information is forgotten but
through rehearsal activity can be sustained and if enough time passes activity
causes structural change – permanent and solid; responsible for lt memory
best evidence for this comes from events that dirsupt brain functioning
retrograde amnesia – loss of ability to retrieve memories of one's past,
particularly episodic or autobiographical, that occured just before episode
“closed-head injury” - brain bumps on inside of skull
hypothesis assertions:
st and lt memory are physiologically different
all information gets into lt only after passing through st
most important factor determinig whether paritcular piece of information
reaches lt memory is amount of time it spends in st memory
The Levels of Processing Hypothesis
Craik and Lockhart – pointed out that act of rehearsal may effectively keep
information in st memory but does not necessarily result in establishment of lt
memories
suggested that people engage in 2 types of rehearsal: maintenace rehearsal
and elaborative rehearsal
maintenance rehearsal – rote repetition of verbal information; repeating a
given item over and over again; serves to maintain information in st memory
but not necessarily resulting in lasting changes
elaborate rehearsal – preocessing information on meaningful level, such as
forming associations, attending to meaning of material, thinking about it, etc.
Craik and Tulving – demonstrated effectiveness of elaboration in
remembering by giving people set of cards containing printed sequence
including missing words denoted by blank line and found that participants were
twice as likely to remember sentence if word was of medium or high
complexity
suggest that memory is more effectively established if item is presented in
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