PS4529/30PS4529/30ApplicationsApplicationsof Cognitiveof CognitiveNeuroscienceNeuroscience

Do ERPs revealDo ERPs revealmodality specific retrieval processes?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 auditory episodeRecall visual episode

As retrieval ends…

As retrievalbegins…

ERP Modality Experiment: ConclusionsERP 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

ConsolidationMechanisms

AttentionalControl

Encoding Storage Retrieval

AttentionalControl

SemanticRecords

PerceptualRecords

Binding

ContextSemanticRecords

PerceptualRecords

Binding

Context

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)

Can we control what we 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)

Target context easy (exp 1) vs. hard (exp 2) to recollect

0 600ms 0 600ms

+

5µV

TARG NONTARG NEW

Exp. 1

Exp. 2

LEFT RIGHT

Herron and Rugg (2003)

ERP data when control exerted over recollection

(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)

Bottom line

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.

ERPs as ‘memory detectors’..?

Brain Fingerprinting

http://www.brainwavescience.com/HomePage.php

“…The Brain never lies…”

“…99.99% for sure…”

“…Find the MERMER and you’ve found the Murderer…”

“…the infallible witness…”

Farwellian view on Cognitionand 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 Multi-faceted 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 scene-

relevant 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. Has the science been tested? 2. Has the science been peer reviewed and published? 3. Is the science accurate? 4. 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/

0,13026,1176809,00.html

•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

Key Issue: The supposed objectivity of scientific neural data vs. the subjectivity of

personal report

Questions and Answers?