Author Archives: emilyrmurphy

What a dead salmon reminds us about fMRI analysis

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This has been making the rounds in the neuroscience world, but deserves attention in cross-disciplinary fields.  A group of top-notch fMRI researchers presented an unusual paper at June’s Human Brain Mapping conference.

Paper titleNeural correlates of interspecies perspective taking in the post-mortem Atlantic Salmon: An argument for multiple comparisons correction

Blog headline: fMRI Gets Slap in the Face with a Dead Fish

Salmons have very small brains.

Salmons have very small brains.

In short, researchers scanned a dead fish while it was “shown a series of photographs depicting human individuals in social situations. The salmon was asked to determine what emotion the individual in the photo must have been experiencing.”

Clearly, the fish did not perform well at the task, and thus we have not learned much about interspecies perspective taking.  The work is, however, a compelling and humorous demonstration of the problem of multiple comparisons.  This is a principle in statistics that basically says when you’re looking at enough bits of information (i.e. doing lots of statistical tests), some will seem to be what you’re looking for – purely by chance.  In fMRI experiments, there are a LOT of pieces of data to compare, and without statistical correction for this phenomenon (which is not always done), some will indeed be significant, just by chance.

Lead author Craig Bennett explains further on his blog:

In early 2008 I was working with my co-adviser George Wolford on a presentation he was giving regarding the multiple comparisons problem in fMRI. We were discussing false positives in MRI phantom data and I brought up the idea of processing the salmon fMRI data to look for some ‘active’ voxels. I ran the fish data through my SPM processing pipelines and couldn’t believe what I saw. Sure, there were some false positives. Just about any volume with 65,000 voxels is going to have some false positives with uncorrected statistics. Rather, it was where the false positives occurred that really floored me. A cluster of three significant voxels were arranged together right along the midline of the salmon’s brain.

Remember that the fish was dead.  There was surely no BOLD signal changes going on in a dead fish’s brain.  This is likely not a physiological artifact; it is a statistical one.  Furthermore, the voxels were clustered together – something that may be expected to happen in an “actual” activation and thus used as a threshold for analysis.  Also, it was just one fish!  (No apparent speculation in the paper about what may have happened if this were a school of fish compared to appropriate control school of fish.)

Bennett et al are apparently having a hard time getting the paper published.  The use of multiple comparisons corrections in fMRI studies is a contentious one, as some researchers think it may be overly conservative and thus miss true positives.  As a solution, Bennett suggests reporting both sets of data, corrected and uncorrected.

The moral of the story for interdisciplinary folks: note whether multiple comparisons correction data have been reported (or not).  And always bear in mind that there are a lot of assumptions and decisions being made behind the ultimately reported data in any neuroimaging study.

- Emily Murphy (h/t Alexis Madrigal @ Wired)

Update on Indian BEOS case: Accused released on bail

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We wrote in December about the murder trial in India that relied heavily on Brain Electrical Oscillations Signature (BEOS) test to prove that Aditi Sharma had “experiential knowledge” of the poisoning of her former fiance, Udit Bharati.  Aditi and her husband, Pravin Khandelwal, were sentenced to life in prison. The original opinion, which we believe contains many serious flaws, is available at the original post.

We recently learned, courtesy of some research by Rajat Rana (thanks to Vinita Kailasanath!), that Aditi and Pravin have been granted bail by the Bombay High Court (documents: Aditi’s bail order and Pravin’s bail order).  Pravin’s sentence was suspended on the grounds that there was no real evidence to tie him to the case as a conspirator. Aditi was released based on the fact that the evidence of her possessing the arsenic-laced prasad was not compelling, and indeed “the possibility of plantation cannot not be ruled out” (sic). The BEOS evidence is not mentioned in either brief.

Watch this space for further news and a complete analysis.

- Emily Murphy

More on No Lie MRI case

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David Washburn at the Voice of San Diego has reported on the No Lie MRI case, with some choice quotes from the CEO of No Lie MRI, Joel Huizenga.

We hope to learn more details about the case and the offered evidence soon, so watch this space.  In the meantime, for background reading on fMRI-based lie detection, Hank Greely and Judy Illes published a comprehensive review in the American Journal of Law and Medicine (2007, vol 33, pp. 377-431).

- Emily Murphy

No Lie MRI being offered as evidence in court

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It has come to our attention that No Lie MRI has produced a report that is presently being offered as evidence in a court in Southern California.  A hearing about the admissibility of this evidence is imminent.

The case is a child protection hearing being conducted in the juvenile court.  In brief, and because the details of the case are sealed and of a sensitive nature, the issue is whether a minor has suffered sexual abuse at the hands of a custodial parent and should remain removed from the home.  The parent has contracted No Lie MRI and apparently undergone a brain scan.  The No Lie MRI-produced report reads in part as follows:

sanitized1

The defense plans to claim the fMRI-based lie detection (or “truth verification”) technology is accurate and generally accepted within the relevant scientific community in part by narrowly defining the relevant community as only those who research and develop fMRI-based lie detection.  [Note: California follows its own version of the Frye test of admissibility, not the current federal test under Daubert.]

Limiting the “relevant community” to only those who research and develop fMRI based lie detection is without merit, if only because such a definition precludes effective or sufficient peer-review.  Indeed, it is arguable such a narrowly-defined community has a strong incentive to exaggerate its claims of accuracy and overlook unanswered questions for financial gain if such techniques are “legally admissible.”

The few practitioners who research and develop fMRI-based deception detection are not the only qualified people to comment on the accuracy and validity of the technique.  Statisticians familiar with Bayesian analysis, cognitive neuroscientists familiar with technical and analytical constraints, and researchers working to elucidate the neural basis of memory, decision-making, and social behavior should all make up the “relevant scientific community” for such a complex and as-yet poorly characterized technology.   Further, I suspect the community of peer-reviewers that have reviewed the articles being proffered in support of the evidence of fMRI testing on deception is probably a useful proxy for the legally relevant scientific community, and extends well beyond the handful of researchers working directly on fMRI-based deception detection.

I will post again soon with more details and criticisms about the claims in the statement produced by No Lie MRI – mainly, that their external validation task was inconclusive in the individual, yet the testing proceeded with the case-related probe questions and found to be determinative that the parent was not lying about denying sexual abuse of the child.  Further, that the repetition of three critical questions (as above) four times each seems incredibly unlikely to produce sufficient power to detect a robust neural response that could be accurately classified as deceptive/non-deceptive.

Please add your own views and suggestions, and check back for updates.

- Emily Murphy

Reading Your Mind Video – CBSNews.com

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Here is the video segment from last night’s 60 Minutes segment on the latest neuroimaging work on “mind-reading,” or “thought identification.”  Lesley Stahl talks to CMU researchers Marcel Just and Tom Mitchell and Berstein Center (Berlin) researcher John-Dylan Haynes – pioneers in the field of “mind-reading” using functional neuroimaging and machine-learning pattern classifiers – as well as ethicist Paul Root Wolpe (Emory). The report talks about some of the work that the research groups published in the last year on “thought identification” (tool and dwelling types), intention formation (choosing to add or subtract) as well as potential future uses such as identifying familiarity with a particular place, all using powerful pattern classifiers to interpret complex brain activation patterns.  Wolpe discusses some of the legal and ethical implications, including the “million-dollar question” as to whether brain activation patterns might be considered testimonial evidence, and thus be protected by the 5th amendment, or more akin to other types of biological evidence (such as hair samples, fingerprints, or DNA) that a person can be compelled to submit. The segment also discusses the potential dangers of the persuasive power of brain images, and advises caution and skepticism as the technology develops.

Balancing the probative value against the persuasive power of such information and images as forensic evidence is the topic of a forthcoming paper by CLB fellows Teneille Brown and Emily Murphy. There are still many (unknown) limitations on the technology, particularly for individual, real-world forensic use. However, if Just’s claim of this being ready for prime time within 5 years is correct, a thorough discussion of the legal and ethical implications should be (and, fortunately, seems to be) happening in parallel with technological advances.

more about “Reading Your Mind Video – CBSNews.com“, posted with vodpod
- Emily Murphy

NPR goes cuckoo for neuropuffs

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First, I have to apologize to Slate’s Daniel Engber for borrowing his excellent subtitle.  I have appropriated it here to draw your attention to yet another disappointing use of neuroscience-as-soundbite by a reputable media source.

On Tuesday, public radio served up what was effectively a 30-minute advertisement of a book by marketer Martin Lindstrom, featuring the power of neuromarketing to tell us why we REALLY buy things.  The answer, of course, is in the brain – which is, as Lindstrom writes, “the ultimate no-bulls*** zone.”  “Its really quite simple,” said Lindstrom on the air, referring to using an fMRI scanner to examine what someone is “really” thinking about a particular product.  You just look at the brain’s “craving spot,” according to Lindstrom, the nucleus accumbens, and see if it lights up!  (Unfortunately, the nucleus accumbens “lights up” for many reasons, including the onset of both pleasant and unpleasant noise).

The excerpt from the book available on NPR’s website raises questions that, in fairness, may be answered later in the book.  In the study described, smoker Marlene reported that warning labels on cigarette packages caused her to smoke less. However, once she was in the scanner, her brain apparently told a different story.  Her nucleus accumbens activation in response to the labels was in interpreted to mean that “cigarette warning labels not only failed to deter smoking, but by activating the nucleus accumbens, it appeared they actually encouraged smokers to light up.”  The brief description of the experiment alludes to Marlene also being asked to report her subjective desire to smoke while she was being shown these images, but the conclusion fails to mention how this response correlated and whether it, alone and without the fMRI data, was just as good at revealing whether Marlene really wanted a smoke.  Furthermore, why would anyone expect that the cigarette warning labels, which are undoubtedly cues strongly associated with smoking, suppress craving?  The more interesting and relevant question is whether they suppress actual purchasing or lighting up at the critical moment of decision – the study, as described, does not ask the question whether the labels assist someone in exerting “willful” inhibition on giving in to the craving to smoke.

This issue comes up again and again with neuromarketing.  Greg Miller at Science summarized last fall’s op-ed debacle in the also-esteemed New York Times, reminding us that neuroscientists know that is that it’s not possible to infer a particular mental state (such as craving) from the activation of a particular brain region (such as the nucleus accumbens).  The problem of reverse inference in neuroimaging studies appears to be utterly ignored by the media who disseminate glowing reports of brain scans revealing “truth”.

The point here is not that neuromarketing is useless, though it may turn out to be a massive waste of money if low-tech, less-expensive measures for assessing “true” consumer preference are available.  My real target is not Lindstrom, who seems to be making a killing by peddling this to, among others, McDonald’s, Nestle, Procter & Gamble, Microsoft, The Walt Disney Co., Unilever and GlaxoSmithKline. If those companies care to spend their advertising dollars on neuromarketing studies, no problem, but a return-on-investment analysis may be in order.

The target here is the failure, on the part of NPR, to ask any interesting and moderately scientific questions about whether this stuff really works, or what the caveats might be.  Instead, what happened was that a listener who does not have extensive experience with neuroscience (i.e. most people) was misinformed about the nature of brain imaging and brain function.  (I won’t get started on the “you vs. your brain” rhetoric that plagues this entire genre of neuromarketing and neuropunditry.)

My ethical concern stems from the fear this talk of neuromarketing might inspire in consumers.  (One commenter on the NPR website wrote: “This technology getting more advanced is a really frightening idea.”)  One also wonders whether the reputation of neuroimaging research may be harmed if the public fears that those who have access to it might use it for personal gain at the expense of consumer autonomy.  (We have written about this recently in a special issue of the Journal of Consumer Behavior.)

Please, NPR, when you talk about science, take the opportunity to accurately educate the public about the marvelous complexity of our brains, rather than reducing hard-won knowledge to sound bites.  Especially when those sound-bites are in the marketing service of someone else.

- Emily Murphy

BEOS ruling from Indian court

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Below, you can download the full ruling in the murder case covered by the International Herald Tribune and New York Times earlier this fall, notable for the prosecution’s use of the “Brain Electrical Oscillations Signature test,” (BEOS) to  confirm that one defendant had “experiential knowledge” of the crime.  Two persons were convicted of the murder and sentenced to life in prison. (It is also available at the blog of Anand Giridharadas, the reporter who covered the story.)

We at the CLB are working on our response to the ruling, but we post it here in advance of our thoughts so interested persons may have a chance to read it for themselves first.  Watch this space for our analysis of the opinion and the BEOS technology described therein.  — Emily Murphy

Download the full opinion here