Presentation on theme: "PS4529/30 Applications of Cognitive Neuroscience."— Presentation transcript:
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 l Studied SEEN items l Studied HEARD items l Unstudied NEW items ERP retrieval effects for each sensory modality:- l SEEN – NEW difference l HEARD – NEW difference Allan, Robb and Rugg (2000), Neuropsychologia,
No! ERPs are insensitive to differences in modality at retrieval Recall auditory episodeRecall visual episode As retrieval ends… As retrieval begins…
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 Consolidation Mechanisms Attentional Control EncodingStorageRetrieval Attentional Control Semantic Records Perceptual Records Binding Context Semantic Records Perceptual Records Binding Context
Exclusion tasks (following Jacoby, 1991) Exp. 1Blocked Encoding. Block 1: Generate a sentence incorporating each word Block 2: Rate each word for pleasantness Exp. 2Blocked 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?
NewTargetNon-Target Exp (0.05)0.76 (0.16)0.83 (0.06) Exp (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
0600ms0 + 5µV TARGNONTARGNEW Exp. 1 Exp. 2 LEFTRIGHT 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. Farwells 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 Page.php …The Brain never lies… …99.99% for sure… …Find the MERMER and youve 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 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 Bs life (e.g. Bs Birthday party at Boscos 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 persons 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 Farwells scientific basis to that for the introduction of a new drug In principle? If someone doesnt generate a MERMER, what can be concluded if we dont know what functions it reflects? Is the distinction between what the person knows or reports versus what their brain reports meaningless?
Readings Farwells website –Particularly his research subsection Review Dan Schacters work on memory errors –7 sins paper from proceedings of the royal society –Neural bases of true and false memory –See also Ken Pallers recent work Gonsalves and Paller (2003) Media portrayal –http://www.guardian.co.uk/life/feature/story/0,13026, ,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