Download Working Memory, Cont`d Sensory Memory Classic “Modal” Model of

2/8/2017
Sensory Memory
Working Memory, Cont’d
• Iconic Memory (Visual)
• Echoic Memory (Auditory)
• These short sensory traces
get maintained in memory
– Short-term / Working Memory
– Long-term Memory
Information
Theory
Classic “Modal” Model of Memory
• Claude Shannon
(1916-2001)
• Atkinson & Shiffrin (1965)
– 3-store model of memory
• “A Mathematical
Theory of
Communication”
(1948)
Photo: Alfred Eisenstaedt .1963. TimeLife
“Coffee-house Internet passwords”
What strategies did you use?
• (In the old days, this might be phone numbers…)
• Rehearsal – repeating item to yourself over
and over
• Chunking – re-coding the list into larger
“chunks”
•
•
•
•
•
4 characters:
6 characters:
8 characters:
10 characters:
15 characters:
ST83
1M3MZ5
8RS4OFB9
M9TLUKDM2D
SDXF5L2F36EH1M2
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Chunking
Chunking
• Try to remember the following string:
• Get all that?
149162536496481100121
Chunking
What strategies did you use?
• How about if you divide it up into more
meaningful chunks?
• Rehearsal – repeating item to yourself over
and over
• Chunking – re-coding the list into larger
“chunks”
1, 4, 9, 1 6, 2 5, 3 6, 4 9, 6 4, 8 1, 1 0 0, 1 2 1
12, 22, 32, 42, …, 112
• Potentially no limit to memory if chunked
repeatedly
• Also notice loss (not a strategy) —
When you didn’t need the information
anymore, you cleared your working memory
7±2
7±2
• George Miller’s landmark 1956
paper
• How much information can
human memory carry?
• Uses Information Theory terminology:
“bits of information”
• Bits of information for simple tasks
roughly the same regardless of modality
– Think binary: 3.25 bits = 23.25 = 9.5…
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7±2
7 ± 2 Chunks
• But! Words have more information in them than
single letters…
• How does this affect number of items in memory
span?
• It doesn’t
• Can recode information into larger chunks
• Number of chunks is always around 7 ± 2
A closer look…
• Miller’s paper is foundational, but lacks
complexity
– Are all items in the list equal?
– How does speed of information transfer affect
memory?
– How does memory change with task demands?
Outline
• Types of Memory
– Sensory Memory
• Memory Capacity
• Memory Features
• Working Memory
(Much of the following material from the
supplementary readings)
• Excellent book
from expert
memory
researcher
Alan Baddeley
• Over the years
pushed &
shaped our
understanding
of short-term /
working
memory
Alan Baddeley
(1934 – present)
University of York
img: https://en.wikipedia.org/wiki/Alan_Baddeley
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Serial Position effects
Serial Position effects
• Remember the 15 character password?
• Which characters were easiest to remember?
• Primacy – the first items are privileged
• Recency – the most recent items are privileged
Primacy & Recency hold
over longer lists, too
Explanation?
• Modal Explanation
– First items get rehearsed most
– Items moved to LTM when buffer is full
– Most recent items still stored in STM/WM
What happens if we…?
Serial effects – slowed presentation
• Slow down presentation, to allow more time
for rehearsal?
• No effect on
recency
• Pre-recency
items recalled
better
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What happens if we…?
Serial effects - Delayed recall
• Slow down presentation, to allow more time
for rehearsal?
• WM decays over time…
• Recency effects
are removed
– What if we delay recall?
What happens if we…?
Serial effects - Intervening Tasks
• Slow down presentation, to allow more time for
rehearsal?
• WM decays over time…
• Demo-• Try to remember the
following items
– What if we delay recall?
• What about interfering with maintenance?
Serial effects –
Phonological Similarity Effect
• List 1
– Contain?
• Tan?
• Cap?
• List 2
– Contain?
• Day?
• Bug?
• Now count back from 201
by 3
• Also blocks recency
•
•
•
•
•
•
•
•
•
•
Wave
Arm
Ice
Cat
Middle
Egg
Blood
Window
Metal
Garden
Serial effects –
Phonological Similarity Effect
List 1:
•Man
•Can
•Cap
•Map
•Pan
•Tap
•Cat
List 2:
•Pit
•Leg
•Day
•Top
•Cow
•Pen
•Hot
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Serial effects –
Phonological Similarity Effect
• Phonological
Similarity
leads to
poor recall
• Semantic
similarity
has a
small
effect
Phon.
Sim.
Phon.
Disim.
Semantically
similar
Sem.
Disim.
Immediate Recall Vs. Learning…
• In this experiment (Baddeley, 1966)
– With longer lists (can’t fit all into memory)
– If participants have to wait 20 minutes before
recall…
• Phonological Effects disappear
• Semantic Effects (synonyms) get larger
• Phon. Effect has to do with rehearsal
Outline
2nd Reading
• Types of Memory
• Highly influential
researcher in
attention and
short-term
memory
• Watch for him
again in Attention
lectures!
– Sensory Memory
• Memory Capacity
• Memory Features
• Working Memory
Donald Broadbent
(1926 – 1993)
Applied Psychology Research Unit
UK Medical Research Council
Dates: https://en.wikipedia.org/wiki/Donald_Broadbent; img: http://www.mrc-cbu.cam.ac.uk/timeline/images/broadbent.jpg
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7 ± 2?
7 ± 2 chunks
• Braodbent (1975)
• There are some pretty good reasons to doubt
that ~7 is the short-term capacity
• Bits of information for simple tasks
roughly the same regardless of modality
• Let’s re-examine Miller’s evidence…
7 ± 2?
Primacy & Recency hold
over longer lists, too
• Let’s re-examine Miller’s evidence…
• And in the Recency effects…
– Recall: recency is tied to keeping things in your
rehearsal loop
7 ± 2?
• Let’s re-examine Miller’s evidence…
• And in the Recency effects…
– Recall: recency is tied to keeping things in your
rehearsal loop
Q F X S
R U V M
L J D B
4!
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7±2?
7±2?
• Broadbent also mentions:
• Perfect Performance
• On average, people can recall about 7 digits
from a list
• But how many can people almost always
recall?
• Broadbent also mentions:
• Modal Performance
• For lists of categorical items (foods, cities, etc.)
most lists people come up with are 2-3 items
long
– About 3-4
7±2?
7±2?
•
•
•
•
• Broadbent also mentions:
• Running Memory
• RM for manual gestures (not digits)
seems to max out at about 3
Broadbent also mentions:
Running Memory
You hear a list of items
When I pause, give me as
many of the last items as
you can recall
• Last: 0 3 1 10 6 7
Pollack, I., Johnson, L. B., & Knaff, P. R. (1959). Running memory span. Journal of experimental Psychology, 57(3), 137-146.
7±2?
Several different stages?
•
•
•
•
• 7±2 comes from being able to perform some
chunking of information
• And from combining
• When rehearsal is blocked, 3-5 items seems to be
about the limit
• May be limited by Attention
Broadbent also mentions:
Clustering
If you monitor pauses in peoples’ recall
They pause longest between clumps of ~3
items
• Suggests we can only select ~3 items at a
time, and then we chunk them
• Will see more evidence in lectures on Attention!
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Several different stages?
Primacy & Recency hold
over longer lists, too
• Broadbent suggests memory is divided into
different “Stages”
• (His exact formulation is a bit uncertain)
• But let’s look at the serial position curves
again:
Serial effects - Delayed recall
• Recency effects
are removed
7±2?
• Initial Items are pretty robust over time
• These may be in Long-term memory
• Last items are easily disrupted
• These items are lost from an active, working
memory store
7±2?
Parts of the Working Memory System?
• Separating these out, working memory
appears to have a capacity of ~3-4 items
• Baddeley & Hitch (1974) – Working Memory
• 7±2 comes from chunking and use of longterm storage
•
•
•
•
Auditory
Visual
(Episodic Memory)
Central Executive
– (Planning and setting goals)
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Phonological Buffer
• Subvocalization
• Can repeat things in Echoic Memory –
up to a few seconds
– Used in language
– Sounds may be more time-dependent than
images, since sound inherently unfolds over
time
Visuo-spatial Sketch Pad
• Evidence:
– Visualizable words are easier to learn
• See also: Object-based Mnemonics
– Spatial problem-solving aided by visual
“working space”
Episodic Memory
• Combines elements into a single story
or “episode”
• Evidence:
– People with Severe memory damage can still
process individual sentences
(sentences longer than Phonological Buffer)
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Central Executive
Brain activation?
• Coordinates behavior of the buffers
• Keeps systems “on task”
• Turns off subsystems after task is over
• Curtis & D’Esposito (2003)
• Dorsolateral Prefrontal
Cortex (DLPFC)
• Propose 4 major areas
for working memory:
– (P) Parietal areas
• Evidence from people with frontal lobe
damage
• Some evidence from people with hippocampal
damage
• Stores information for
location of objects
– (F) Frontal Eye-Fields
• Visuospatial buffer
– (B) Broca’s Area
• Phonological buffer
– (D) DLPFC
• Central Executive
Clive Wearing
BBC – Man Without a Memory
Clip: https://www.youtube.com/watch?v=Vwigmktix2Y
Deep Thoughts…
Long-Term Memory (LTM)
We are our memories.
Without our memories, we are
creatures of mere sensation.
-d.r.
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Outline
When people think of “memories”…
• Types of long-term memory
• Often think of specific things / events
– Implicit / Explicit
• How do we store?
My first ride on
a roller-coaster!
Date of signing of
US Constitution
• What do we store?
My best friend’s
middle name
• How durable is the store?
My worst break-up
Capitol of New
York?
Explicit Memory
Semantic memory –
not tied to specific
time or place
Date of signing of
US Constitution
My best friend’s
middle name
Capitol of New
York?
My favorite birthday
party
Memory is also Implicit
Episodic memory –
tied to specific events
My first ride on
a roller-coaster!
My worst break-up
My favorite birthday
party
• Processes / Procedural Memory
– How to ride a bike
• Classical / Operant Conditioning
– Learned changes in behavior
• Priming
– Giving little bits of information to produce faster
recognition
Priming: example
Priming: example
• Dell’Acqua &
Grainger
(1999)
• A masked
stimulus is
presented too
fast for
conscious
identification
• Decision task
on word at
end:
• Is it a natural
or man-made
object?
• Compare when
Prime is
semantically
Related or
Unrelated
– A “Prime”
Dell'Acqua, R., & Grainger, J. (1999). Unconscious semantic priming from pictures. Cognition, 73(1), B1-B15.
Dell'Acqua, R., & Grainger, J. (1999). Unconscious semantic priming from pictures. Cognition, 73(1), B1-B15.
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Priming: example
Memory is also Implicit
• Responses are
faster when
primed with
same category
• Responses
slower when
primed with
different
category
• Processes / Procedural Memory
– How to ride a bike
• Classical / Operant Conditioning
– Learned changes in behavior
No
prime
Semantically
Related
Semantically
Unrelated
• Priming
– Giving little bits of information to produce faster
recognition
Dell'Acqua, R., & Grainger, J. (1999). Unconscious semantic priming from pictures. Cognition, 73(1), B1-B15.
Implicit Memory
Outline
• Often a procedure
• Does not require conscious recognition
• Conscious thought may interfere
• Types of long-term memory
• Can measure changes in
reaction / performance
– Implicit / Explicit
• How do we store?
• What do we store?
• How durable is the store?
How are memories stored?
How are memories stored?
• Physical Location?
• Synapse Strength?
• Physical Location?
• Lashley (1950)
– Trained rats on various tasks
– Then lesioned rat cortices in an attempt to find
out where those behavioral memories were
stored
– Couldn’t find them in a single place
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How are memories stored?
• Instead, errors
in learning
increased
with amount
of cortex
lesioned
• Physical Location?
• Lashley (1950)
– “It is not possible to demonstrate the isolated
localization of a memory trace anywhere within
the nervous system. Limited regions may be
essential for learning or retention of a particular
activity, but within such regions the parts are
functionally equivalent. The engram is
represented throughout the region.”
(Definitions)
How are memories stored?
• Engram – The package of information that
makes up a memory
– the bound representation of experienced
events, including: perceptual and conceptual fragments,
• Physical Location?
self-generated thoughts, contextual details, etc…
• Trace – a pointer to the memory for retrieval
• Lashley (1950)
– “every instance of recall requires the activity of
literally millions of neurons. The same neurons
which retain the memory traces of one experience
must also participate in countless other activities.”
How are memories stored?
Hebb 1949
• Physical Location?
• Synapse Strength?
• Classic work of
cognitive neuroscience
• Recall Hebbian Learning?
– Cells that fire together
wire together
• Changing synaptic
potential stores
information
• Lays out Hebb’s
hypotheses on
learning
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Classical Conditioning
Physiology of Mind (Structuralism)
• Wilhelm Wundt
(1832-1920)
Whtvr…
• Sensation does not
differ from ideation
• “Blue is and remains
blue”
(whether sensed or
imagined)
Response is physiological and subconscious
Image and dates: https://en.wikipedia.org/wiki/Wilhelm_Wundt
Hebb 1949
Hebb 1949
• Each neuron has tons
of connections
• Cells fire in networks
• Some cells will be
linked in groups
• These “assemblies” may “reverberate”
Hebb 1949
• Even simple
assemblies might
reverberate for…
half a second?
• Reverb = short term
memory?
• Leads to continued
firing / wiring =
learning?
However, in vivo…
• We can try and record out of
cells during a task
• Do we see lasting reverb?
Tania Pasternak, PhD
University of Rochester
Professor, Neurobiology
& Anatomy, Brain &
Cognitive Sciences,
Center for Visual Science
Bisley, J.W., Zaksas, D., Droll, J.A., & Pasternak, T. (2004). Activity of Neurons in Cortical Area MT During a Memory for Motion Task.
Journal of Neurophysiology. Jan 2004, 91 (1) 286-300; DOI:10.1152/jn.00870.2003
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However, in vivo…
• Record out of MT in
awake monkey
• Monkey sees motion
sample
• Delay
• Monkey responds
“same/different” to
test stimulus
Bisley, J.W., Zaksas, D., Droll, J.A., & Pasternak, T. (2004). Activity of Neurons in Cortical Area MT During a Memory for Motion Task.
Journal of Neurophysiology. Jan 2004, 91 (1) 286-300; DOI:10.1152/jn.00870.2003
However, in vivo…
• Activity drops
off almost
immediately
• Poor evidence
of local reverb
Bisley, J.W., Zaksas, D., Droll, J.A., & Pasternak, T. (2004). Activity of Neurons in Cortical Area MT During a Memory for Motion Task.
Journal of Neurophysiology. Jan 2004, 91 (1) 286-300; DOI:10.1152/jn.00870.2003
Complex interplay of areas?
Distributed Neural Networks
• Remember –
• How could memory be so distributed?
– Lashley: Memory is distributed
– Lots of small changes add up?
Distributed Neural Networks
Distributed Neural Networks
• Formed of multiple layers of “nodes” /
neurons
• Nodes/neurons in one level pass info onto
nodes/neurons in the next level
• Patterns of activation in level thus can cause a
specific pattern of activation in the next group
of nodes/neurons
• Through learning and feedback,
weights between nodes/neurons can change
• This changes the information represented in
the network
• Online demos:
http://www.mitchcrowe.com/visualizingneural-networks/
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Example
Distributed Neural Networks
with Visual
Distributed Neural
Retinal Networks
Areas
• Example: handwritten letter detection
Inferior
• Example:
handwritten letter detection
Cones
Rods &
Ganglion
Cells
Temporal
Areas
Input
V1, V2,
etc…
Conscious
Recognition
How are memories stored?
How are memories stored?
• Synapse Strength? Not everyone agrees
• Gallistel & King (2009)
Randy Gallistel
• Gallistel & King (2009)
• Memories are stored in cellular RNA/DNA
• Caveat!
– There is too little
information at the
synapses
– How can functions
and information
possibly be
maintained over the
lifetime?
– “We have no idea what the machinery might look like that would
transcribe information from a spike train into a neucleotide sequence.
How to gain access to the encoded number is also a mystery. We have
no idea what the machinery might look like that would transcribe a
neucleotide sequence into a spike train. But how it is that a
neucleotide sequence could in principle encode a number is no
mystery at all. Thus, such a proposal, wild as it is, passes the test that
the synaptic plasticity hypothesis fails. And that is progress.” (p.280)
Clinical Cases…
• We’ll stick with the network
approach for now…
• Are there parts of the brain that knock out
storage to LTM?
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Clive Wearing
BBC – Man Without a Memory
Clip: https://www.youtube.com/watch?v=Vwigmktix2Y
Also, H.M. (Henry Molaison)
• 1953, Doctors try experimental surgery to
relieve seizures
• Remove parts of Hippocampus & Temporal
lobe (function then unknown)
• Post surgery, H.M. could no longer form new
memories
E.P.
PBS - American Scientific Frontiers (2004)
https://www.youtube.com/watch?v=7Grh3PeEMIg 3:10 – 11:16
H.M.’s brain online
• http://hm.brainandsociety.org/hm
_web/
Lesion
Cellularlevel
resolution
All suffered damage to Hippocampus
• Hippocampus is part of the limbic system
• Located in the medial temporal lobe
• Essential to moving information from
WM to LTM
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Role of Hippocampus?
Role of Hippocampus?
• How does hippocampus get info from WM to
LTM?
• Unclear.
• But, consider:
• Also note: These were formation of explicit
memories
• What about implicit memories?
– Hippocampus reactivates recent experiences
during “off-line” periods (rest & sleep)
(Sutherland & MacNaughton, 2000; Davidson, et al, 2009)
(Will discuss more in consciousness lecture)
HM –
Mirror Drawing
Role of Hippocampus?
• Also note: These were formation of explicit
memories
• What about implicit memories?
– Implicit memories may rely on other areas
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