Transcript Herron and Rugg (2003)

PS4529/30
Applications
of Cognitive
Neuroscience
Do ERPs reveal
modality specific retrieval processes?
• Subjects SAW and HEARD words at study
• Performed a word-stem (e.g. MOT__) cued recall task
• ERPs were formed to stems completed with
 Studied SEEN items
 Studied HEARD items
 Unstudied NEW items
• ERP retrieval effects for each sensory modality: SEEN – NEW difference
 HEARD – NEW difference
Allan, Robb and Rugg (2000),
Neuropsychologia, 38 1188-1205.
No!
ERPs are insensitive to
differences in modality at retrieval
Recall visual episode
As retrieval
begins…
As
retrieval
ends…
Recall auditory episode
ERP Modality Experiment: Conclusions
• Multiple retrieval processes, active at different times
– Onset ~ 0.5s after retrieval cue!
• Retrieval of ‘visual’ and ‘auditory’ episodes involves
common processes. No evidence for modality specific
retrieval processes.
• ERPs reflect a ‘core component’ of retrieval?
– Changes in neocortical activity driven by the
Hippocampus during early stages of retrieval (prior to
modality specific activations)?
– Or: attention to retrieval products?
Episodic Memory Mechanisms
Semantic
Records
Perceptual
Records
Semantic
Records
Context
Binding
Encoding
Attentional
Control
Perceptual
Records
Context
Binding
Storage
Consolidation
Mechanisms
Retrieval
Attentional
Control
Can we control what we recollect?
Exclusion tasks (following Jacoby, 1991)
Exp. 1 Blocked Encoding.
Block 1: Generate a sentence incorporating each word
Block 2: Rate each word for pleasantness
Exp. 2 Blocked Encoding.
Block 1: Generate a sentence incorporating each word
Block 2: Read each word aloud
Retrieval
Words from block 2 always defined as ‘target context’
Herron and Rugg (2003)
Target context easy (exp 1) vs.
hard (exp 2) to recollect
New
Target
Non-Target
Exp. 1
0.96 (0.05)
0.76 (0.16)
0.83 (0.06)
Exp. 2
0.88 (0.11)
0.63 (0.13)
0.84 (0.08)
Herron and Rugg (2003)
ERP data when control exerted over
recollection
LEFT
RIGHT
Exp. 1
+
Exp. 2
5µV
0
600ms
TARG
Herron and Rugg (2003)
0
NONTARG
600ms
NEW
Bottom line
(1)
ERPs may reveal covert retrieval ‘strategy’
The size of parietal old/new effects reflect
the attention paid to particular retrieval
products.
Neural correlates of remembering are
present, or absent, dependent on strategy
If retrieved information is not ‘task-relevant’, it
wont be attended and there wont be a
neurophysiological sign of its recollection
(Herron and Rugg, 2003)
ERPs as ‘memory detectors’..?
1. Farwell’s claims.
2. Their validity from scientific perspective.
3. The basics of his view on cognition and the
brain.
4. His MERMER technique, the data pattern and
interpretation.
5. Its application in forensic settings.
6. Suggested reading from his web-based
material.
Brain Fingerprinting
http://www.brainwavescience.com/Home
Page.php
“…The Brain never lies…”
“…99.99% for sure…”
“…Find the MERMER and you’ve found the
Murderer…”
“…the infallible witness…”
Farwellian view on Cognition
and the Brain
• What does a criminal always take from a crime
scene that records their involvement with it?
• Their brain
• How is this knowledge expressed?
– By a unique neurophysiological signature called a
‘MERMER’
CMF view of Memory and the Brain
• Subjective experiences of memory reflect a highly
fallible (and malleable) system
– Memories for events that never happened can be
generated
– Memories for events that did happen can be deliberately
forgotten, altered and possibly inhibited.
– Strategic changes during retrieval can eliminate ERP
evidence of recollection in exclusion-type tasks
MERMER
• Memory and Encoding Related Multifaceted EEG Response
• When details of a crime are known to
the suspect, a MERMER will be
detected. A MERMER will not occur in
an innocent subject.
Multiple test for your brain
• Three kinds of information are used to determine whether a
subject has specific crime-related information in their brain:
– Target
– Irrelevant
– Probe
• Target information elicits a ‘yes’ response or a MERMER. This is
used as a control. Irrelevant information will not elicit a MERMER.
A MERMER in response to probe stimulus indicates recognition or
the presence of certain information.
• Targets:
information
the
subject
definitely knows; this can be ensured
by telling the subject before the test
starts.
• Irrelevants: information that subject
definitely does not know; this can be
ensured by simply making up the
information
• Probes: information relevant to the
crime or situation, which the subject
may or may not know.
Journal of Forensic Sciences (2001)
• Involving 3 pairs of subjects (A/B), who knew each
other
– Days beforehand, ‘A’ (the informer) was interviewed about
events in ‘B’s life (e.g. B’s Birthday party at Bosco’s diner).
– ‘B’ was tested on this information (probes)
• Knowing
– ‘A’ from another pair was tested on the same stimuli
• Unknowing
- All subjects were given a list of Target stimuli prior to
the test
- ‘Exclusion’-type test instructions
Subject 1
(Knowing)
Subject 6
(Unknowing)
Prior and succeeding MERMER work
• Knowledge of FBI acronyms
– Farwell reports 100% accuracy in discriminating FBI
trainees from non-trainees.
• knowledge in the public domain about the MERMER
technique
–
–
–
–
US PATENTS
Internal CIA reports
The JFS study
A couple of conference abstracts
Forensic Applications of MERMER
• Harrington case
– 26 years into life sentence
– MERMER for alibi-relevant probes but not crime scenerelevant probes
– Key prosecution witness hears about this and changes
testimony
– Harrington goes free!
– IOWA supreme court rules such evidence is admissible in
court
• JB Grinder case
– Led to a conviction
• JR Slaughter case
Forensic Applications of MERMER
•
The ‘Daubert’ standard used by the IOWA
supreme court:1.
2.
3.
4.
Has the science been tested?
Has the science been peer reviewed and published?
Is the science accurate?
Is the science well accepted in the scientific community?
Key scientific issues to consider
• Farwell quite clearly does not deny the imperfection of
human memory
– An eyewitness testifies to the the content of their memory,
not to the truth of what happened.
• But he believes that the MERMER reveals
– “… what IS present in a person’s brain.”
– This makes no sense, whatsoever, without knowledge of
the function revealed by the MERMER
– What function(s) does the MERMER reflect?
• The Daubert criteria imply that there is a clear answer to this
critical question
A Scientific evaluation
1. Has the science been tested?
A little, by Farwell
2. Has the science been peer reviewed and published?
Twice, I think.
3. Is the science accurate?
Unknown
•
Is the science well accepted in the scientific community?
By definition, it cannot be.
Is the MERMER an Old/New ERP
effect?
• Inadequate work on neurophysiology of
– MERMER
• What is its scalp distribution?
– Very long-term memory retrieval
• Possible lack of Hippocampal involvement during retrieval
• Lack of distinct recollective qualities
• Preponderance of ‘interpretation’
– Repeated retrieval of single ‘episodes’
• Almost nothing known…
Is Farwell right or wrong to apply his
technique with this level of
knowledge?
• Are moral considerations relevant?
• On empirical grounds?
– Compare Farwell’s scientific basis to that for the
introduction of a new drug
• In principle?
• If someone doesn’t generate a MERMER, what can be
concluded if we don’t know what functions it reflects?
• Is the distinction between what the person knows or
reports versus what their brain reports meaningless?
Readings
• Farwell’s website
– Particularly his research subsection
• Review Dan Schacter’s work on memory errors
– 7 sins paper from proceedings of the royal society
– Neural bases of true and false memory
– See also Ken Paller’s recent work
• Gonsalves and Paller (2003)
• http://troy.psych.northwestern.edu/~cnl/
• Media portrayal
– http://www.guardian.co.uk/life/feature/story/0,13026,117
6809,00.html
Key Issue: The supposed objectivity of
scientific neural data vs. the subjectivity of
personal report
•If accuracy / truthfulness matter, then
personal report cannot be trusted
Motivation to lie
Unreliability of memory
Even if valid testimony is given,
issues of personal responsibility
and lapses of self-control still arise
Questions and Answers?