The Cognitive Neuroscience

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The Cognitive Neuroscience Of True and False
Memories Daniel L. Schacter Harvard University
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Against All Enemies

• Mr Clarke The Secret Service asked for fighter
  escorts to protect Air Force One.
• Mr. Miller He himself asked Condoleeza Rice
  whether to call up fighter support and she said
  to go ahead.
• Mr. Clarke Mr. Miller urged Secretary Rumsfeld
  to take a helicopter out of the Pentagon.
• Mr. Miller He never talked to Mr. Rumsfeld that
  day.

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Cognitive Neuroscience of
Memory Distortion (Schacter Slotnick,
Neuron, 2004) What brain regions are involved
in monitoring or reducing memory errors? What
type of brain activity is associated with the
generation of inaccurate memories? Can brain
activity distinguish true vs. false memories? The
sensory reactivation hypothesis What are the
neural origins of memory errors?
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Norman Schacter, 1997
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Sensory Reactivation Hypothesis
True memories are characterized by greater
access to sensory/perceptual details than are
false memories reflects reactivation of
sensory/perceptual encoding for previously
experienced events. Behavioral evidence
Studies of post-event misinformation (Schooler et
al., 1986) and false recognition (Mather et al.,
1997 Norman Schacter, 1997) access to
sensory/perceptual details greater for true than
false memories.
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Sensory Reactivation Hypothesis Neuroimaging
Evidence
Truegtfalse increases in DRM paradigm Subjects
intially hear lists of semantically related
words, tested visually with old and new
items Truegtfalse increases at retrieval in
auditory cortex suggestive of auditory
reactivation (Schacter et al., 1996). However,
later research suggests that truegtfalse
activation may depend on exact format of
recognition test (blocked v. intermixed Johnson
et al., 1997 Schacter et al., 1997).
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FMRI of True and False Recognition Basic
Procedure
(Cabeza et al., 2001)
Participants study lists of semantically
related words (half of
the lists are semantic associates from Roediger
McDermott,
half are categorized lists)
Each list presented alternatively on videotape
by either a male
or female source
Participants instructed to try to remember
words as well as
which speaker presented them
Scanned during old/new recognition test
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True vs. False Recognition of Shapes
(Slotnick Schacter, Nat. Neurosci, 2004)
Previous results suggest greater sensory
reactivation during true recognition compared
with false recognition. We tested this idea by
assessing event-related activity in the visual
cortical processing stream during true and false
recognition of visual shapes.
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Study Phase

• For each of 3 runs at study, 144 shapes were
  presented (16 sets of 9 exemplars)
• Each set alternated in spatial position to the
  right or left of fixation
• Pres. Time 2.5 sec

Nonstudied Prototype
Exemplar
Exemplar

• Instructions remember each shape and side of the
  screen

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Test Phase

• For each of 3 test lists, 96 shapes16 sets of 2
  studied exemplars, 2 nonstudied/related shapes (1
  prototype and 1 exemplar), and 2 nonstudied/
  unrelated shapes
• Presented at center for 2.5 sec
• Participants made recognition decision
• old-left, old-right, or new

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Behavioral Results

0.7


0.6
0.5
0.4
P(Old)
0.3
0.2
0.1
0
Old
Related
New
p lt 0.001
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True and False Recognition
Ventral View
Old-hits gt New-CRs (True recognition)
Related-FAs gt New-CRs (False recognition)
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True recognition gt False recognition
Ventral View
Visual recognition-related activity previously
reported in late visual areas (BA19, BA37)
LH
Old-hits gt Related-false alarms
X
Related-false alarms gt Old-hits
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Sensory Reactivation Hypothesis Nature of Visual
Activity?
Results show greater activation for true
than false memories in early visual areas, which
process primitive visual information. Does this
reflect conscious memory for previously studied
shapes? Perhaps recollection of some feature of a
shape - a line segment or color? NO!
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Sensory Reactivation Hypothesis Nature of Visual
Activity?
Early visual activation is the same for
previously studied shapes both when people call
the shape old (indicating memory) and when they
call it new (indicating forgetting). This
finding suggests that a nonconscious form of
memory distinguishes between true and false
recognition. In contrast, later visual areas
that activate similarly for true and false
recognition do reflect conscious memory.
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Cognitive Neuroscience of
Memory Distortion (Schacter Slotnick,
Neuron, 2004) What brain regions are involved
in monitoring or reducing memory errors? What
type of brain activity is associated with the
generation of inaccurate memories? Can brain
activity distinguish true vs. false memories? The
sensory reactivation hypothesis What are the
neural origins of memory errors?
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Cognitive Neuroscience of Memory
Distortion Encoding Origins What
are the neural origins of memory distortion?
Can we tell by examining brain activity at the
time of encoding whether an event will be
remembered accurately or inaccurately? Several
recent studies have begun to explore
this question using subsequent memory designs,
where scanning brain activity at the time of
encoding allows us to predict whether an item
will later be remembered or forgotten.
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Wagner et al., Science, 1998
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Specific Nonspecific Recognition

• Accurate memory is often highly specific, whereas
  distorted memories rely more on general gist of
  what happened
• Specific recognition exact or verbatim memory
  for previously studied item
• Nonspecific recognition general memory for
  gist of previously studied item (Brainerd
  Reyna, 1995 Schacter et al., 1998)
• e.g., false recognition calling related new
  item old

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Specific vs. Nonspecific Recognition Rationale

• We sought to compare
• the neural origins of specific and nonspecific
  recognition at encoding using a subsequent memory
  design
• Key hypothesis
• activity during encoding in the right fusiform
  region, implicated in processing specific visual
  features of objects, will be preferentially
  associated with subsequent specific recognition
• (Garoff, Slotnick, Schacter, Neuropsychologia,
  2005)

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MethodEncoding

• During fMRI scanning
• Participants view 360 nameable objects

• Task Is object larger or smaller than a
  13-inch square box?

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MethodRecognition

• Next day, outside of scanner
• Participants view 450 objects (180 same, 180
  similar, 90 new)

Task Is object same, similar, or new
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fMRI Results Distinct Neural Regions
Specific recognition gt Nonspecific recognition
right fusiform cortex
Z -20

• Supports hypothesis that right fusiform gyrus
  is associated with specific feature encoding
• Right fusiform gyrus is ONLY area to show
  activity in this contrast

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Reality Monitoring and the Brain
Reality monitoring refers to our ability to
distinguish between memory and imagination
remembering perceived events versus things we
only imagined (Johnson Raye, 1981) Studies
using fMRI to measure brain activity during
encoding provide evidence that we can predict, to
some extent, when reality monitoring will succeed
and when it will fail. We examined reality
monitoring for emotional and nonemotional
information.
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Evoking Reality-Monitoring Errors
frog
casket
canoe
snake
Adapted Adapted from Gonsalves and Paller (2000)
Paller, 2000
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Kensinger Schacter (2005), Neuropsychologia

• Memories for emotional events were more accurate
  than memories for neutral events better
  discrimination between seen and imagined objects

• Role of encoding processes?
• Activity in regions that process emotional
  information during encoding increased the
  likelihood of subsequent correct memory
  attributions for emotional but not nonemotional
  items
• - Amygdala orbitofrontal cortex
• Interactions between amygdala and hippocampus
• Important for enhancing correct memory
  attributions for emotional items

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FMRI of True and False Memory Implications for
Witness Testimony?
Is fMRI a truth machine that we can use to
determine the accuracy of witness memory? Not
now (or for forseeable future) -Results apply
to groups, not individuals. -As experimenters,
we know what actually happened in the real
world, we dont know. -However, our results
show that in principle imaging can distinguish
true and false memories.